Saturday, July 24, 2010

Toroceratops


We’ve been hearing rumbling of this paper for awhile now, but it became big news at SVP last year (in Bristol, England, a place I’ll never go back to): Jack Horner and John Scannella proposed a very radical taxonomic synonymy: Torosaurus, that famous long-frilled chasmosaurine, is actually just a very old Triceratops. This isn’t the first time Horner & Co. have applied ontogenetic lumping. Just last year, Horner & Goodwin suggested that Dracorex and Stygimoloch represent teenage and subadult stages, respectively, of Pachycephalosaurus. The paper has been met with mixed support, but this new effort has really split the community. This all seems to be an effort by Horner to show that the Maastrichtian period of the Cretaceous was a barren wasteland, taxonomically speaking, for the dinosaurs, and that diversity was in the crapper well before that giant meteor wiped the last few stragglers out.

And there’s nothing wrong with that. If you really can convincingly show that only one pachycephalosaur, one ceratopsid, one duckbill, and one tyrannosaur existed at the close of the Cretaceous, then yeah, the future looks grim for the Hell Creek dinosaur community. But that can be a tough pill to swallow. Any beefs I have with the Pachycephalosaurus paper have been addressed in an earlier post, so I won’t go too far into detail here. Mainly, I think the authors did a great job is showing that Dracorex is a teenager, Stygimoloch is a subadult, and Pachycephlosaurus is an old man. Those facts alone do not suggest synonymy. A larger sample size, more complete material, and better knowledge of the ontogenetic development of other pachycephalosaurs is necessary to make any kind of truly informed decision about the growth and development of a single poorly-represented genus.

Anyway, let’s talk about Triceratops and Torosaurus. The former is an extremely well-known, well-represented chasmosaurine ceratopsid from all over North America at the close of the Cretaceous. Torosaurus is known from the same deposits, but is extremely rare. Two species are tentatively known: T. latus and T. utahensis. The latter species was originally regarded as a species of Arrhinocertops by Gilmore, and, in fact, Horner & Scannella suggest that original classification may well bear out.

The authors based most of their claim on a paper from a few years ago by Horner & Goodwin which proposes an ontogenetic series for Triceratops. Key features of this growth series are the changing orientation of the brow horns and the eventual blunting and reabsorption of the epiparietals. The Horner & Goodwin paper details five distinct growth stages, though I do wonder about individual variation. Do all teenage Triceratops have slightly recurved brow horns? Would the brow horns really change orientation from basically straight as a baby to recurved as a teenager to forward-pointing as an adult? It just seems like a stretch. I’m all for horn growth, but I also know, from studies on centrosaurine ontogeny and bone beds, that ceratopsian exhibit a large degree of individual variation. Horner & Goodwin even acknowledge this when discussing Triceratops’ epiparietals, but we’ll get to that in a minute.

The point is that Torosaurus represents a sixth distinct growth stage, wherein the frill changes shape considerably—from wave-shaped in cross section to basically billboard-shaped and elongate, with squared-off upper corners instead of a nice round shape. Additionally, two large fenestrae appear as parietal bone is reabsorbed. Only as a full-grown adult does Triceratops come to resemble most of its chasmosaurine relatives. Apparently this all happens very quickly during the animal’s life, and there are no “in-between” specimens, although Horner & Scannella suggest that the oft-neglected Nedoceratops (Diceratops), with its incipient parietal fenestrae, may represent just such a “transitional” form.

The authors are quick to point out that the structure of the frill is the only skeletal feature that separates Triceratops from Torosaurus, but even this isn’t actually evidence for synonymy. If that’s your only justification for lumping two ceratopsids together, you may as well toss the entire Chasmosaurinae (except maybe Chasmosaurus) under one genus. It’s been repeatedly demonstrated that the parietal bone is the single most important bone in the ceratopsid body for providing taxonomic identification. Arrhinoceratops, Anchiceratops, Torosaurus, Mojoceratops, and Ajugaceratops all look pretty much the same beyond the parietal, although that last genus does have distinct brow horns. If anything, history has shown the safe bet—when it comes to horned dinosaurs—has been to split rather than lump.

Scott Sampson agonized over the decision to place Einiosaurus and Achelousaurus in different genera, since their parietals are so similar, or take Einiosaurus out of Styracosaurus in the first place, which is where it had informally sat for so long. Just recently, another “species” of Styracosaurus has been renamed as Rubeosaurus ovatus. A critical part of each of these decisions has been that the structure of the parietal bone. In Einosaurus and Achelousaurus, Scott eventually came to conclusion that, based on the fact that the former had a big hooked nasal horn while the latter had a roughened pachyrhinosaurine boss was enough to separate them at the generic level, although he briefly toyed with the idea that they merely represented sexual dimorphs of each other! This is how much the parietal bone means in ceratopsid taxonomy!

So, stating heroically that the structure of the frill is the only thing separating Triceratops from Torosaurus, as if that means something, is superfluous and misleading because you could say the same about any two other chasmosaurines or any two centrosaurines. It’s a good thing those two subfamilies differ in more than just parietal anatomy or we’d all be screwed.

Horner & Scannella also point out that Triceratops skulls are ridiculously common, and in fact so many are known that a convincing growth series has been established for the genus. By contrast, Torosaurus is amazingly rare, but it is known from the same time and places that one finds Triceratops. They take this to mean that Torosaurus must represent a very aged Triceratops, but that living such a long and fruitful life must have been a miracle given the rarity of that genus vs. the dozens of Triceratops specimens. I have problems with this for two reasons. First, just because an animal is uncommon doesn’t mean it doesn’t actually exist (taxonomically speaking). Nobody is accusing Bagaceratops or Udanoceratops to be a juvenile or full adult of Protoceratops, even though they’re ridiculously rare by comparison. I’m actually surprised Horner hasn’t tried synonymizing the two species of Protoceratops. Anyway, it’s entirely possible that Torosaurus preferred different environments than Triceratops, which would make sense if they’re going to avoid direct competition, and that environment might not be prone to fossilization. I’ve heard it argued that ceratopsids have such a great fossil record because they liked near-shore environments that increase their chances of being fossilized. Surely they didn’t all live the exact same lifestyle, and it’s possible that Torosaurus habitually lived in a different area than Triceratops. It’s also not fair to say that “no juveniles of this genus exist, therefore this genus must not exist.” I can name dozens of dinosaurs that aren’t known from juvenile forms, yet their validity is not doubted!

The second reason is that I doubt Triceratops would put a ton of effort into suddenly expanding its frill when death occurred so close to that period. As the authors acknowledge, Torosaurus skulls are very rare, yet juvenile, subadult, and adult Triceratops skulls are unbelievably common. Why would “old adult” Triceratops (Torosaurus) be so poorly represented? Horner & Scannella suggest that the mortality rate was higher among non-Torosaurus-stage Triceratops, but I have a hard time believing that. Such a strange survival separation isn’t seen in other ceratopsids—why would it be any different for Triceratops? That is to say, other ceratopsids have pretty equal survival rates, no matter what their growth stage. Triceratops doesn’t?


While the authors focus on Torosaurus latus, one may wonder about how they rectify Torosaurus utahensis. They question how many specimens of T. utahensis are diagnosable to the genus level, and even if it is valid, they throw up their hands and say that it’s a southern species of Triceratops, a different genus, or Arrhinoceratops—which it was originally referred to. Time will tell, I suppose, although Hunt & Lehman (2008) have stated that T. latus and T. utahensis are nearly indistinguishable, and in fact can only be discriminated based on the structure of the squamosal/parietal suture. Is Triceratops also present in Utah? I’m not sure, myself, but it might say something about Toroceratops.

Let’s talk about ontogeny. Horner & Scannella posit that Triceratops retains a paedomorphic condition of a solid frill well into adulthood, but what is the basis of determining that a solid frill is a juvenile trait? In centrosaurines, even the youngest animals have small parietal fenestrae. What about chasmosaurines? Are juvenile and subadult animals known chasmosaurines? Certainly, that Ajugaceratops bonebed can shed some light on this, but I haven’t read much on it. Apart from that concern, Horner & Scannella make a good case for the possible development of fenestrae in Triceratops over time. They discuss several specimens that have thin or sunken areas of the parietal where the bone is uniquely textured. I think this is good positive evidence that actually does make a correlation between Triceratops and Torosaurus. An alternate explanation is that they are actually describing juveniles or subadults of Torosaurus! Despite pointing out a lot of Triceratops skulls that have thinning areas of the parietal, the authors do not or cannot show a “transitional” frill, where the parietal fenestrae is present, but very small, and surrounded by thinning bone and a rim. If the bone was reabsorbed (as it must have been), it would have been reabsorbed from the inside out, so skulls should exist that have circular thinning sections with a small perforation at their center.

Next, the authors discuss squamosal elongation in Triceratops. A series of squamosal bones are shown: almost all of them are recognizably Triceratops: L-shaped. Figure I is interpreted as being from Triceratops, but it looks very similar to figures J and K, which are labeled Torosaurus. The authors are trying to show a purported growth series, but to my eye, the Triceratops squamosals are very obviously different from the Torosaurus squamosals. Worse, a line graph showing squamosal elongation is shown (Figure 4). Triceratops subadults and “young adults” cluster around the center, as expected, but the Torosaurus individuals fall way to the right of everything else. There are no Triceratops or Torosaurus specimens straddling the gap between the two genera. It’s very obvious that Torosaurus squamosals are very different than Triceratops. Plus, one Torosaurus squamosal (ANSP 15192) sits above the cluster of Triceratops squamosals. It’s recognizably Torosaurus but is similar in length to subadult and “young adult” Triceratops? To my mind, that means Torosaurus is fundamentally different than Triceratops at a similar age.

The authors also discuss epiparietal and episquamosal morphology. In the Horner & Goodwin Triceratops paper, the authors observe that Triceratops’ epiparietals and episquamosals become incorporated into the edge of the frill over time, and that older adults no longer have spiky frill edges, but more scalloped edges where the epiparietals and episquamosals are tab-like and rounded. In every known specimen of Torosaurus where epiparietals and episquamosals are preserved, they are also heavily absorbed. However, there are some key differences. Whereas the epiparietals and episquamosals of adult Triceratops are tab-like and rounded, those of Torosaurus are elongate and somewhat flattened, with distinct squared-off edges instead of rounded edges. Did the episquamosals and epiparietals elongate along with the frill bones? I doubt it. Their distinct morphology really does seem distinct.

Torosaurus specimen ANSP 15192 is particularly interesting because it appears to represent a subadult Torosaurus: its nasal horn morphology pertains to an early growth stage based on Horner & Goodwin’s Triceratops paper, and its frill is not as long as MOR 1122 or YPM 1831, yet it still has parietal fenestrae. Of course, Horner & Scannella recognize the analogy with Triceratops but ignore the nasal horn morphology: “No ‘Torosaurus’ specimen has posteriorly curving postorbital horn cores, which would be indicative of immaturity.” However, ANSP 15192’s postorbitals do conform very well to figure (d) of that paper—what you might call a young adult. And guess what? That’s where its squamosal sits on Figure 4 of Horner & Scannella’s paper. In that same growth stage (d), the epiparietals and episquamosals of Triceratops are starting to fuse and become rounded.

I’d talk about the bone histeology of the frill, as that’s one of the more interesting aspects of the paper, but I don’t know enough about bone histeology to do so intelligently.

Horner also seems married to the idea that the dinosaurs were dwindling in diversity at the end of the Cretaceous, and he’s been whining that paleontologists have been overstating the diversity of the Hell Creek Formation for years. That very well may be, but his solution is to synonymize everything that comes out of the ground. Look at what we used to have: Nanotyrannus, Tyrannosaurus, Dracorex, Stygimoloch, Pachycephalosaurus, Triceratops, and Torosaurus. Diceratops has always been questionable. Now we might just have Tyrannosaurus, Pachycephalosaurus, and Triceratops. I’m not against that idea, I’m just saying that extraordinary claims require extraordinary evidence. While the idea that Torosaurus represents the “silverback” stage in Triceratops’ lifecycle may hold merit for future study, I don’t think that Horner & Scannella proved it beyond a reasonable doubt.

Discuss!

EDIT: Can I stop pressing Control-I now?

75 comments:

Ian said...

Great post. One thing that really bugs me is that on a forum I frequent, most of the members are acting like this is the end and that Torosaurus is officially sunk. That is not the case at all! All that has happened is the paper proposing such has been published. That's it! It's now time for people to read and analyze the arguments and see if they hold up, as you have just done. To just say "That's it, it's settled" is not good science, and, in my opinion, something of a cop out from doing any real critical thought.

Dino Hunter said...

I would comment on your post (which I agree with), but I think I'll write a rebutal and see if I can get it published.

Traumador said...

i'm thinking the geographic distrubtion of torosaurus vs. triceratops is the key...

triceratops is found in some places that torosaurs are not... the idea of the adult form being so rare you only find them in a few spots compared to sub-adults found everywhere is ridiculus... however if it can be shown the two always coexist and ONLY ever coexist (not appear in places seperate from each other... which triceratops currently does) i'll be more convinced.

definately more work needs to be done on this, with more refined studies of end cretaceous sites done to try and determine whether the two are truely linked or not...

weird changes in ceratopsians are known. baby pachyrhinos have horns that later grow inward to form the boss, which is really whacky. so i guess a solid frill becoming hollow isn't totally impossible, but still seems counter intuitive...

Mike Keesey said...

"If that’s your only justification for lumping two ceratopsids together, you may as well toss the entire Chasmosaurinae (except maybe Chasmosaurus) under one genus"

That's really not a terribly crazy idea, anyway. Look at Phrynosoma: http://digimorph.org/resources/hornedskulls.jpg

Brad said...

Is there any irrefutable evidence of two or more chasmosaurine taxa coexisting in the same ecosystem at any point prior to Triceratops? Most of them do seem stratigraphically and/or geographically segregated from each other. The stratigraphic range of Mojoceratops in Alberta does appear to overlap with Chasmosaurus, however (as I understand it- prove me wrong!).

It's unfortunate that Tatankaceratops was published too late for consideration in this study.

Andrea Cau said...

"This all seems to be an effort by Horner to show that the Maastrichtian period of the Cretaceous was a barren wasteland, taxonomically speaking, for the dinosaurs, and that diversity was in the crapper well before that giant meteor wiped the last few stragglers out."

This may be true only assuming that the Hell Creek Ecosystem WAS the whole Earth in the Late Maastricthian. Who knows what the rest of North America and Laurasia and Earth were...

It is also possible that the Heel Creek ecosystem reflects only a North American r-oriented condition (few species with a broad ecological and gepgraphical renge), geographycally limited to (part of) North America.

Please, do not see a single Formation as The Entire World...

dinogami said...

he’s been whining that paleontologists have been overstating the diversity of the Hell Creek Formation for years. That very well may be, but his solution is to synonymize everything that comes out of the ground. Look at what we used to have: Nanotyrannus, Tyrannosaurus, Dracorex, Stygimoloch, Pachycephalosaurus, Triceratops, and Torosaurus. Diceratops has always been questionable. Now we might just have Tyrannosaurus, Pachycephalosaurus, and Triceratops.

...and:

NON-AVIAN THEROPODS
-------------------
* whatever theropod made Saurexallopus tracks
* the as-yet undescribed caenagnathid (?Chirostenotes) that now resides at the Carnegie Museum
* the Hutchinson & Chiappe alvarezsaurid
* Richardoestesia, whatever it is
* Troodon
* Dromaeosaurus
* Saurornitholestes

ANKYLOSAURIA
-------------
* Ankylosaurus
* Edmontonia

ORNITHOPODA
-----------
* Thescelosaurus
* Edmontosaurus
* Anatotitan (of questionable distinction, I know)

CERATOPSIA
----------
* Leptoceratops

...and probably others I'm missing. Of course, there's no biostratigraphy within the Hell Creek involved here; I found it rather interesting in Sampson & Loewen's chapter in the new ceratopsian volume how few ceratopsians (either chasmosaurine or centrosaurine) co-occur in the same bio- or chronostratigraphic ranges even in the same areas; seems to point to a very rapid turnover between ceratopsian species. I'd be curious to see the stratigraphic distributions of Triceratops and Torosaurus specimens...

Trish said...

Couldn't read the bits about "(number) growth stage" without this madness suddenly appearing in my mind:

"What's this?"

"Ungehhh-EEEH!!!"*

"Triceratops is evolving!"

(Runt-dunt-dunt-dunt-dunt Dunt-dunt-dunt-Da! Dunt-dunt-dunt-dunt-dunt...)

"Congratulations! Your Triceratops evolved into Torosaurus!"

* - My best onomatopoeia of a certain fictional triceratops with an odd growth stage of her own. *Is* there any evidence of baby trikes having but one horn?

Zach said...

I agree, Andrea. I'm certainly curious about how the dinosaurs were doing in the rest of the world (and even the USA).

Dinogami, there certainly was lots of ceratopsid turnover, but there are some occurances of overlap between two members of the same subfamily (Mojoceratops & Chasmosaurus, for instance), so it's not unheard of.

Nima said...

Hehe I think you can all guess what I think of Horner's new Torosaurus theory (and all his theories about cretaceous dinosaur ontogeny)... TOSS IT OUT!

And if you think the whole WORLD was a dino-diversity black hole in the Maastrichtian, you're badly in need of a trip to Argentina (and Madagascar, AND Mongolia, AND I'm guessing a half-dozen other countries...) Hell Creek was not representative of the entire earth. Most continents were far better off than North America. Sure it wasn't their heyday either, but they were FAR from going to Hell (Creek) in a Handbasket!

What's REALLY funny is that Horner wasn't putting out his lumper-extremist ontogeny theories in earnest until after the Pokemon card franchise came out at the end of the '90s. Coincidence?

Triceratops will "evolve" into Torosaurus when exposed to an Earth gem. Put stage 2 card on top of the basic Pokemon. Upgrade hit points from 70 to 100.

In all honesty though, do you know of ANY land animal that goes through as many insanely different growth stages as Horner's ceratopsians and pachycephalosaurs? I mean at least all of the ACCEPTED growth stages of Triceratops look like each other in all basic aspects. No frill holes, no crazy spikes or radically different shapes.

It looks like Horner's whole philosophy of dinosaur classification and growth stages is more dependent on ocean sunfish than dinosaurs or their close relatives.

qilong said...

Certainly an excellent post. I should be cautious, however, when dealing with attempting to overturn this paper on the example of proscribed parietal evolution. While Scannella and Horner can be faulted for over-extrapolating an ontogenetic series past the point it seems viable, they may be wholly correct in everything save their specific examples. The authors specifically address the issue of parsimony by claiming that it is more reasonable to assume that there is only one taxon available than two (or more). This is the main point of Horner's declining ecosystem theory, and one which needs to be severely addressed.

Christopher said...

The amount of ignorance from certain people here is outstanding! And I'm sorry Zach, but you critique is hardly any better. Really it seems like your entire argument boils down to "I dont fully understand what they are saying, but since Horner is that guy who thinks T. rex was a scavenger then this must be just another of his ridiculous theorys."

In this paper we are shown clearly how the parietal fenestrations of Torosaurus develop, and they develop in mature aged individuals. Further more only established and accepted mechanisms for this development are evoked. We are also shown that there are no specimens of Triceratops out of several hundred that exist which exhibit a bone texture indicative of maturity, and that many of these specimens also exhibit parietal changes that are remarkably similar to what is seen in the earliest stages of fenestration in Torosaurus. It is also known that all specimens of Torosaurus exhibit a mature bone texture. Further more, though I dont think that Scannella illustrated this as well as he could have, you do see the sort of gradual squamosal/parietal lengthening and widening in Triceratops that is being proposed here. Also, Its not really a stretch to see a high mortality rate in young adult individuals with only a few of such reaching maturity.

Im not sure where the idea that Triceratops is found in areas that Torosaurus isnt comes from but unless there is a reference that some one can point me to, this isn't known and all we do known at the moment is that Triceratops and Torosaurus both come from the Hell Creek formation. Certainly the strat should have been addressed first but the histological argument is sound.

So you could have two sympatric species of giant ceratopsian running around the Hell Creek environment. The two are otherwise indistinguishable (probably, we havent found juviniles or young adults of one or mature individuals of the other) until one species reaches maturity and develops its characteristic features. But at some point parsimony needs to take over. Multiple species can not be the null hypothesis because it cant be falsified. Every new specimen could potentially be a different species when you are only dealing with the level of resolution you get in fossils. This is not scientific. Until such a time that a juvenile specimen that is unquestionably Torosaurus which is also morphologically different than same age Triceratops, or alternatively a specimen of Triceratops exhibiting all the histological markers of maturity and none of the morphological characters of Torosaurus is found; Torosurus is sunk.

qilong said...

Christopher,

In response to at least one aspect of your reply to Zach, I would like to note that as the argument of both Scannella and Horner and Farke's work (from which it follows), fenestration appears to result in chasmosaurines in the same manner as one another; Triceratops lacks the classic fenestration because, unlike other chasmosaurines, the frill was much shorter at that ontogeny.

Note, however, that Scannella and Horner do not (as yet) place the relative fenestration due to age into a broader context, but in the context that Torosaurus COULD derive from Triceratops. They conclude, nonetheless, that the fenestration provides proof of age-class differentiation due to species overlap. The authors do not, but propose that further work will support, that stratigraphy of material will further show how the species can be related. As such, while the authors do NOT synonymize the taxa (which requires Torosaurus latus and Triceratops horridus to be synonymous) but recognize that T. prorsus and T. horridus are distinct, one can easily argue from this that the fenestration is chasmosaurine in nature, not species specific, and variation that exists between the species can support the validity of latus apart from either prorsus and horridus. If it does, one cannot assuredly synonymize Torosaurus and Triceratops.

Horner and Goodwin admit similar difficulties in being unable to actually lump Pachycephalosaurus wyomingensis with Stygimoloch, due to the clear morphological disparity, but try to lump them in with one another nonetheless. The practice can only be supported with an a posteriori conclusion to which the data is aligned to agree with.

D. Esker said...

A quick peak at the PBDB (www.paleodb.org) to look at the geographic ranges for Torosaurus and Triceratops reveals the following:

Torosaurus is found in:
Alberta
Colorado
North Dakota
South Dakota
Texas
Utah
Wyoming

Triceratops is found in:
Alberta
Coahuila
Colorado
Montana
North Dakota
Saskatchewan
South Dakota
Wyoming

That is a pretty substantial overlap, albeit not a perfect one -- it is more or less what I'd expect the relativly greater abundance of Triceratops. This isn't totally conclusive -- I'll need to see if there is any consistent difference in environment of deposition betwixt the two.

Zach said...

Chris, if I had to boil my response down to a few key points:

1) Who's to say that a solid frill is a juvenile character for chasmosaurines?

2) The fact that all Torosaurus specimens currently known exhibit adult frill morphologies isn't necessarily indicative of a relationship with Triceratops. It just means they're aduls. And what about that pesky "juvenile" Torosaurus?

3) Let's see some postcranial work on both animals.

4) The structure of the parietal is a bid deal when it comes to ceratopsid taxonomy, and both the parietal and squamosals of Triceratops are obviously distinct from Torosaurus.

5) I didn't mention this in the post because it was getting too long, but the frills of Triceratops and Torosaurus are fundamentally different shapes. Triceratops' frill curves up and is somewhat rounded; Torosaurus' sweeps back and is squared-off.

That's quite a transition.

The Whale Boy said...

Zach, Scannella and Horner are pretty explicit in their treatment of the "Juvenile Torosaurus" - it doesn't have any actual juvenile characteristics aside from small size. It has adult characteristics instead (flattened epi's, forward pointing postorbital horns, etc.).

WRT your distinction between the epiparietals/episquamosals of Torosaurus and Triceratops - I suggest you really look at some actual skulls of each and try to tell them apart yourself. I don't work on dinosaurs, but I've been shown enough of these things to the point where I would be highly, highly suspect of anyone attempting to discriminate between the two.

How exactly are the parietal and squamosal distinct in these two taxa? I'm sorry, take another look at that figure with all the squamosals; the thought of someone pointing at any of those and saying "look how different they are! They must be a different genus!" is laughable.

As far as stratigraphic and geographic ranges does - just look at the units in the southwest where T. utahensis (which just as well may be Arrhinoceratops again as has been suggested) - the sample sizes are abysmally small; they'll mean something when more (and better) material is uncovered. Otherwise - the largest sample size of Torosaurus and Triceratops IS the Hell Creek Formation (and the Lance); hence why this study was conducted there and not in the southwest.

Before any of these tenuous morphological arguments in support of Torosaurus being a different taxon are advanced any further - I highly recommend reading up a little on bone growth and histology, and re-reading that other half of the paper that has thus far been ignored.

Lastly - what I want to know is this: why is there so much resistance to ideas concerning dinosaur growth? The implications are extremely interesting - suggesting that these critters drastically change the shapes of their skulls through ontogeny; Jack had a pretty interesting talk on metaplasia in dino crania at SVP in Bristol (I thought that was a really fun meeting). We already know from Horner and Goodwin (2006) that Triceratops already does all sorts of weird stuff with its head (changes the shape of the postorb. horns, flattens epis, etc.); what Scannella & Horner suggest really isn't that radical.

So - why are people so resistant? Because dinosaur nerds don't want their precious childhood memory of "Torosaurus" to be sullied (Oh no! It's no longer Torosaurus, my childhood memories are dying) or is it because of a more complex, problem in dinosaur paleo? Are other paleontologists scared because their favorite pet genera and species they've named and collected like so many postage stamps or action figures will be synonymized, and threaten their reputation? Or is it because researchers have of late been trying to overemphasize dinosaur diversity? Seriously, just look at Coahuilaceratops; what the hell is that? A bunch of non-diagnostic fragments? I think the problem relates to "taxonomic greed" in dinosaur paleontology right now, and I'm glad I'm not a part of it.

Anonymous said...

Whale Boy@ The same could be said of why everyone is jumping on the 'Torosaurus is Triceratops bandwagon.' Is it just because Jack is an author on the paper. I think more people are jumping on the bandwagon just because of that fact, "Jack worship" and not based on the merits of the study.

Nima said...

These freewheeling Hornerites posting on here are forgetting one thing - circumstantial evidence by itself does not prove a theory. There is not a single irrefutable line of evidence in their argument.

They reason like lawyers instead of scientists.

Lawyers try to make a case through persuasion and emotion based on twisting the evidence that exists to support their argument - they already have a pre-determined case, then they go about selectively picking and spinning evidence to favor it.

Scientists on the other hand go on an evidence-before-conclusion basis - no assumptions, look for possible "false positives", discard anything that is falsified... THEN formulate a cohesive theory. At least that's what GOOD scientists do.

The Hornerites violate this several ways.

First, just because Triceratops and Torosaurus are found MOSTLY in the same areas, it does not prove that they are one and the same. Try finding some other late Maastrichtian ceratopsian that's NOT from these locales - you get Pentaceratops, which is the REAL closest cousin of Torosaurus.

Second, simply because Triceratops experiences changes in skull shape as it grows older, that does not imply a radical change in frill shape and huge amounts of bone reabsorption which would be necessary to turn it into a Torosaurus. Some of you guys should take a good look at a triceratops skull. The frill is insanely thick, both in small and large individuals. Horns and small studs do change form, but there has NEVER been a case in the proven growth series of Triceratops of the entire head changing form, or of fenestrae forming.


Thirdly - indeed, fenestrae are a primitive basal characteristic of ceratopsidae, as both centrosaurines and chasmosaurines have it. Torosaurus is simply an inheritor of that legacy, whereas Triceratops replaced the fenestrae with a solid frill.

Fourth, if you ignore the heads, the bodies of chasmosaurine ceratopsids are nearly identical in most aspects. Yet we don't lump them all into one genus, since the different skulls clearly show different sorts of specializations and growth patterns. Torosaurus is one of many "variations on a theme", Triceratops is another.

Fifth, nobody has ever done any kind of bone-ring dating of a Torosaurus's age. So we may have young adult Torosaurus, instead of an old Triceratops.

Sixth, the claims of Hornerites are far too circumstantial. There is no "transitional" stage that shows a Triceratops head morphing into the Torosaurus configuration. Simply in terms of biology, it makes no sense for a full-grown Triceratops to undergo such a rapid ontogenic change so late in life, without any real change in overall size. There are no living or extinct parallels. Were we to find even one well-preserved juvenile Torosaurus (apparently there is an partial one already), Horner's theory is KIA.

Finally, no Torosaurus specimen has fully double curved brow horns like adult Triceratops. They all have forward-curved, Pentaceratops-like horns, or straight-tipped horns like Triceratops adolescents. Are Hornerites suggesting that Triceratops horns suddenly reverted back to their adolescent/juvenile condition in old age? PLEASE EXPLAIN WHY.

Nima said...

And I agree with anonymous, there is a lot of blind "Jack Horner worship" going on these days.

Basically it seems to me like Horner is trying to cast himself as the new "maverick" of Paleontology (in ways that are often almost the opposite of Bakker). The problem is that, in the rush to make a name for themselves (or remake, in Horner's case) many researchers end up hastily tacking their credentials to some pretty laughable theories and reconstructions.

This goes for Horner, Kristin Curry-Rogers, Dale Russell, Kent Stevens, as well as all your more notable BANDits (Larry Martin, Alan Feduccia, etc.)

Horner's theory of T. rex as a cold-blooded scavenger obviously hasn't stood the test of time and peer review. So he has switched gears. But it's all too obvious that his pursuit of taxonomic lumpery has a greater overarching motive - to "prove" that the end of the cretaceous was a time of terribly un-diverse dinosaur faunas.

Except Horner was a bit late - about a quarter of a century too late. You see, Bakker conclusively proved in 1986 that the last faunas of Late Cretaceous North America were terribly un-diverse. He even charted their decline, as the Mongolian immigrant Saurolophus edged out 80% of the native fauna, only to be itself replaced by Triceratops a few million years later.

However, Bakker didn't dare to assume that all the planet experienced such destabilized ecosystems. South America was not very hard-hit, neither was India. He admitted that the asteroid impact was what finished off the dinosaurs, though in North America they were already doing badly.

Horner seems to be taking it a step further, and lumping like crazy to make the collapse of the faunas seem even more rapid and eliminate even the need for an asteroid impact. I suppose he would blame climate change or other "slow" factors.

But he's overlooked too much, and made too many empty theoretical constructs under the banner or "hard science", recasting himself as a radical far too late - remember, this was the same man who for decades regurgitated the same tired myth that T. rex was cold-blooded and too slow to hunt prey, and still hasn't disowned that claim. Reminds me of John McCain. A "maverick"? Yeah right! A stodgy change-resistant old guard, attempting to ignore his past 20 years and invent any unfeasible idea to court young acolytes. And at such a cost of credibility!

Ian said...

Nima, what do you have against Kristi Curry-Rogers? Also, while I agree that there is a lot of "Jack Horner worship" these days, but I've noticed that there is also a lot of the opposite, with people dismissing his ideas just because of who he is. Neither position is very good. The former is an appeal to authority, and the latter is a form of ad hominem attack. Both of these are serious logical fallacies. We should try to evaluate Horner's theories as objectively as we can, setting any personal admiration or prejudices aside. As for myself, I still like to actually read the paper and see what is said.

The Whale Boy said...

Nima et al.,

1) It isn't a very radical change in shape of the frill. The squamosal may be slightly longer, but the only difference in the parietal is the presence/absence of fenestrae.

2) We already have a triceratops growth study that shows the head changes shape. Go back and read Horner and Goodwin (2006).

3) Scannella and Horner have done a more general histologic study. Go read up on histology, and re-read that part of S/H 2010.

4) Of course you can't see a transitional stage! They either have fenestrae or they don't, and that means either Triceratops or Torosaurus - that's a real convienent strawman. They in fact do show such a transitional specimen where there is a zone of thinned bone right where the parietal fenestra forms. Second, they histologically showed that that part of the frill is undergoing resorption in large triceratops.

5) "Double curved" postorbital horns: Again, you really need to reread Horner and Goodwin's paper. Juveniles have posteriorly curved horns, adults have anteriorly curved horns, and the s-shaped horns are transitional between the two. So, no shit that Torosaurus doesn't have those - because they're all adults. Great job shooting yourself in the foot.

6) I don't give a rats ass if Horner is on the paper or not. I respect the guy; it's one thing to buy into something someone says just because of who they are. However, just because you have some weird ass chip on your shoulder that Horner is satan incarnate or something doesn't make your automatic rejection of his ideas any better. Just remember: this isn't Jack's paper. This is John Scannella's paper.

The simple fact remains that these guys have done the most exhaustive study of triceratops to date, and have utilized one of the largest sample sets available for dinosaurs (Re: skulls). No one else has even attempted to use histology as a tool for something like this (well, except Horner and Goodwin, and other Goodwin papers). I haven't heard a single decent argument here that even remotely topples their hypothesis.

I'm serious: why is there so much reluctance to even consider the possibility they might be right? Taxonomic greed? What I've seen with these comments suggests something far more sinister as the ad hominem attacks suggest - the rejection of ideas just because someone's pissed off that Horner suggested that everyone's favorite carnivorous dinosaur didn't behave the way we imagined when we were five years old? You can't deny that said suggestion hasn't spurred all sorts of new research into theropod paleobiology.

And I'm not a hornerite. As my name implies, I'm a goddamn mammal person, and thank god for that.

Nima said...

@ Ian

I have nothing against Kristin Curry-Rogers personally. Rather, she approved and endorsed Mark Hallett's highly flawed skeletal reconstruction of Rapetosaurus, which is so far the most significant animal associated with her name. Which I find astonishing in light of the face that she had firsthand access to the fossils.

@ Whaleboy

You really need to tone down the personal grievances. You claim you are not a Hornerite but then tell me "no shit, you just shot yourself in the foot" and made insinuations that anyone who disagrees with you is exhibiting "greed" and five-year-old immaturity, accusing me of thinking Horner is satan, or what have you.

I don't claim to know anything good or bad about the man personally, only his theories. Bad science is bad science, I don't much care whether it's under the name of Horner, Martin, Feduccia or anyone else. All I ever said is he's got a lot of poorly supported conclusions and most of his followers blindly act like lawyers to make it looks like he's always right. And just because Scanella isn't Horner, that doesn't mean he's always right either. The fact you accuse me of so much hot air, in such a fashion, makes it pretty clear you're not very good at hiding your fanatic Horner-worship.

I myself prefer Bakker's and Greg Paul's ideas, but at least I am humble enough to admit I do disagree with them on some areas, and you never see ME repeatedly swearing at and insulting anyone who doesn't agree with them. It's easy to tell from our style of debate, who is standing on sound science and who is the vitriolic fringe group follower.

This is probably the main reason why Hornerites, BANDits, Creationists, etc. have lost credibility - bellicose patronizing language, and refusing to have any credible disagreement with their idol. Strange as it may seem, I'm not closed off to the possibility of Horner being correct - I doubt any of his opponents are that dogmatic. However, unlike you, I'm EQUALLY open to the possibility that he's dead WRONG. And so far that possibility is looking a lot more weighty in light of the evidence.

Also, your analysis of triceratops growth stages is off. Double curved horns are not normally a juvenile or adolescent feature, they are the fully grown adults. Look at Scott Hartman's skeletals, his adolescent triceratops actually has straighter horns than most full grown adults (for which you could easily go to a museum or consult Greg Paul's skeletals). In some cases the horns seem to actually straighten out before they recurve.

There's a further wrinkle complicating things - there actually DO seem to be 3 different species of Triceratops (not 16, and not 1 either). T. horridus has the double curved horns as an adult and is quite large. T. prorsus looks similar but is smaller and with a more compact frill and more pronounced epoccipitals (generally a larger nose horn too). T. elatus is large like T. horridus, but with a flatter frill, reduced epoccipitals, and nearly straight horns. None of them show a transition to a Torosaurus-like frill shape. Also, the frill of Torosaurus has often been badly reconstructed. It's more square than in most photos.

T. elatus is the most "Torosaurus"-like species, and also resembles Eotriceratops in many ways. But it's NOT Torosaurus.

Torosaurus has some unique features besides the shape of the frill. The brow horns are proportionally a lot shorter than in any adult triceratops, and also feature a prominent groove on the outer side - a feature also found in Pentaceratops, but NOT Triceratops. Indeed, the extreme forward curve of the horns is also like Pentaceratops, more curved than in any adult Triceratops specimen.

Nima said...

continued:

Torosaurus is basically just the last conventional fenestrated Chasmosaur, probably closest to Pentaceratops and Anchiceratops rather than Triceratops. If that sinks your notion of one glorious ceratopsian genus at the end, so be it. I'm not in love with either possibility, realistically it makes no difference in my life, precisely how many ceratopsian genera were stomping around 65 million years ago. I only care about the actual science, so your accusations of 'not wanting to give up what I learned as a kid' are the real straw man.

BTW, since you are apparently a fan of whales, look at how many genera and species of whales there are, even today in a time when whales and mammals in general are in evolutionary doldrums. We're hardly in the "golden age" of mammal diversity, genetically or otherwise. There are over 40 genera of Cetacea in 14 families.

Don't expect me to simply believe that there was ever only one genus of Ceratopsidae in the Maastrichtian. Pentaceratops proves that idea wrong, and the juvenile Torosaurus specimens do as well.

The Whale Boy said...

Nima: I'm sorry I used cuss words. I'll keep it professional. I'm not expecting to make you believe anything, but thus far you haven't brought a single valid argument to the table.
My comments regarding dinosaur fanboys were targeted toward a much larger group of people than just yourself, so I apologize for that misconstruction.

To address your other concerns:

1) So what if Scott Hartman drew a Triceratops skeleton with double curved horns? I'm talking about real fossils, real skulls - not artwork. Like I said - the largest skulls of triceratops have horns curved forward, as do those of torosaurus; the smallest have them curving posteriorly, and ones kinda in the middle have the s-shaped curve. We already know based on histology that bone is being resorbed and added in different places on the horns, and it totally jives with the known ontogenetic trajectory of Triceratops. That's what the fossil record (i.e. not a couple of drawings) shows...

2) I'm not quite sure if your observation about the length of Torosaurus postorbital horns is valid or true; both Toro skulls at MOR have pretty long postorbital horns. Also, an MOR triceratops skull (nicknamed "Mort") has way shorter horns; so horn length is probably fairly plastic, as you would expect.

I agree - further studies need to be done on what species of Triceratops are actually valid, and the stratigraphy and geography of these Maastrichtian ceratopsids; we should wait for the publications, though.

RE: Cetaceans - certainly, there is quite a morphological diversity among cetaceans, and cetacean diversity peaked in the middle-late Miocene. Anyway, I'm not a fan of whales; I just go out and dig them up, and publish actual research and stuff.

Christopher said...

I am being called a "Hornerite" and its me who is on the side supposedly arguing from a emotional based position? Really now? For one thing, I dont care what Horner says about T. rex, it doesn't have any baring on his morphological work. Secondly this is John Scanella's work.

They aren't arguing like lawyers, they are arguing like Scientists. The evidence isn't meant to be irrefutable. And it isnt based on an a posteriori conclusion to which the data is aligned to agree with. A hypothesis has been advanced to explain the current otogenic disparity between Triceratops and Torosaurs, and similarly within the complex of Hell Creek Pachys. Evidence in the form of histological and morphological data suggests that there is merit to the hypothesis and, at the moment, there is nothing that directly contradicts the hypothesis. Of course there is much in the way of circumstantial evidence put forward in support, such is the majority of palaeo, and alone each individual piece can not stand alone. Taken as one cohesive body of evidence, however, its quite damning.

"OH, but they look so different" or "thats just too much of a change." Etc. are not valid arguments. Quantify that difference. Its already well accepted that the skulls of Triceratops go through radical changes from hatchling to young adult(even if you cant agree that toro and trike are the same, all large Trike skulls are still only young adult) show me exactly why that the particular change from large Trike morphology to Toro morphology is suddenly some how TOO too much. Or why its actually impossible for the mechanisms they evoke to result in such a change. These are valid points to consider if want me to take your ad hominem arm waving seriously. Ultimately Toro = Trike is a falsifiable hypothesis, Toro and Trike are sympatric species is not. Its falsifiable for the reasons I've already stated previously. And that is what matters.

Christopher said...

Now I'll address some of the points you guys brought up.

If by juvenile Torosaurus you mean the Philadelphia skull (ANSP something or other), its not a juvenile Its a small adult. Small size is not a good indication of ontogenic age, especially with older animals. This has been the case for some time now. There are Trike skulls that are as big or larger than MOR 1122, but have all the markers of a juvenile ontogenic stage.

I dont know whether a solid parietal is in fact a juvenile characteristic for Chasmosurines, making the parietal of Triceratops paedomorphic. And I dont know if there are specimens to support this unequivocaly. That said, It wouldn't surprise me at all. There are precious few young juvenile ceratopsians known. Triceratops probably has the most after Protoceratops, which does have solid parietals as a hatchling. The only other young juvenile cranial material that Im aware of is Brachyceratops and Avaceratops, which both have only tiny incipient parietal fenestra at best, the region is not well preserved. Both are also larger than the UCMP baby trike, but that may not mean anything though it is suggestive.

There are no other LATE Maastrichtian ceratopsians. Pentaceratops is at most early Maastrichtian. And what studies have found Torosaurus to group with Pentaceratops?

Bone ring dating? By which I assume you mean the studies on T. rex by Erickson et al. Do you understand how metaplastic bone re absorption works? It needs to be done with post crania, on elements such as the ribs which undergo little to no remolding to be valid. And there simply isnt enough associated skulls with post crania to make such a study worth while.

What makes the particular Triceratops ontogenic series of your choice "proven?" The "entire" head doesn't change, just the post orbital horn cores, which is just a continuing trend in the re absorption and deposition seen in younger stages, and squamosals and parietals, which again is just a continuing trend from younger stages. And really, there has "NEVER" been a case? care to quantify that?

You say that the bodies of chasmosurines are nearly identical. I call bullshit, its just untested, and nobody has bothered to try. Just another example in a long long list of unsubstantiated claims in palaeo. They have said the same about Hadrosaurids and Iguanodontians in the past as well.

"Fenestrae are a primitive basal characteristic of ceratopsidae, as both centrosaurines and chasmosaurines have it. Torosaurus is simply an inheritor of that legacy, whereas Triceratops replaced the fenestrae with a solid frill." Well, yes that is the old standard. However, that was the prevailing theory simply because there wasn't any evidence to support any alternative hypothesis. Enter new data, more specimens, better understanding of phylogeny and ontogeny and you can now begin to formulate a more encompassing hypothesis based on actual evidence rather than just the lack of it.

Christopher said...

Sorry about the double post, I cant seem to delete it. Anyway here is the closing of what I have to say.

What makes the frill of Triceratops so fundamentally different from Torosaurus? Certainly there are specimens which can be said to exhibit a "wave like" morphology. Theres the Triebold specimen, the specimen at the smithsonian which was re cast and enlarged to become the Hatcher mount. But there are many other morphologies some very short and rounded, almost sadle shape, there are also varing degrees of elongation similar to the AMNH skull. You cant pick a single morphology amoung a spectrum, claim it represents the charachteristic condition and then use it as a point to argue your position.


"There is no transitional stage" Really? Really Really? You want to use that argument? Actually there are a lot. Seriously, like a few hundred. The double curved brow horns that you claim exemplify adult Trikes, are the brow horns in transition from the juvinile posteriorly curved morph to the adult morphology of forward curvature. You may notice that there is a spectrum to the degree of double curvature as well as to how straight the curvature is. This occurs because the bone is being reabsorbed at the tip, where you still see some of the juvinile signal, and deposited at the base, where you get the adult signal, at different rates.


There is no partial Juvenile Torosaurus. Unless of course you would like to provide me with a reference. Until such is provided, its unsubstantiated gossip or worse. If it is the case, and holds up to scientific rigour, great! Why is it so difficult for people to understand that science is not about the truth, its about what is best supported by the current evidence. If more evidence shows up that contradicts previously supported theory, thats just scientific progress. Thats how Science works.

Nima, your rhetoric reads like you lifted it right out of the creationist mad libs book of arguments against evolution. You need to do better.

Df9465 said...

It's important to get facts right, 'cause people do read these blogs and often take what they read at face value. I don't feel like this is a very good post on the Trike-Toro paper at all. It is almost entirely opinion, and uninformed opinion at that. Many of the facts are wrong or misrepresent the primary research. I started writing some point for point corrections, but there are too many.

but @Nima: A lot of your facts are also wrong. As a start, read up on Pentaceratops. I think you will be surprised by just how wrong your statements are.

Zach said...

I permentantly deleted your double-post, Chris. It happens to me, too. Don't know why--it's a Blogger thang.

Let's not get into fisticuffs, gents. Whaleboy, I'm not really "against" the idea of Torosaurus not being a valid taxon, I'm just playing devil's advocate, bringing up points where I either disagree or (probably) don't know any better.

I stand by my frill-shape thing that I brought up earlier, though (in a previous comment). Scott and I were discussing this tonight over dinner, and we agree that there is a sharp contrast between the shape and geometry of "adult" Triceratops frills and Torosaurus' frill. In centrosaurines, at least, overall frill shape remains consistent through ontogeny.

df9465 said...

Christopher's points are well made.

@zach: Centrosaurine frills do change shape through ontogeny, and they also remodel/gain various spikes and adornments.

Other chasmosaurines change the shape of their frill through ontogeny, you just have to read the literature to find the examples, since the papers are not specifically about ontogeny.

Zach said...

@Df9465: Centrosaurine frills change in more of a "grow outward" way. Yes, they add spikes, but the fundamental geometry of the frill does not change. In Triceratops' case, the frill curves upward and is rounded. In Torosaurus, the frill is backswept, flat, and subrectangular.

I can see the Torosaurus frill growing from a juvenile Triceratops frill, because it hasn't curved up yet, but, I mean, look at the shape and geometry of an "adult" Triceratops frill, then look at a Torosaurus frill. You'd have to renovate the fundamental geometry of the thing.

Nima said...

Christopher, venting at me like that doesn't help advance science, nor does it make any of us look good.

I am being called a "Hornerite" and its me who is on the side supposedly arguing from a emotional based position? Really now? For one thing, I dont care what Horner says about T. rex, it doesn't have any baring on his morphological work. Secondly this is John Scanella's work.

Really? Did I call you out by name as a "Hornerite"? I don't recall ever having met you, isn't it a bit too soon to start making enemies and accusing me of personal attacks? Perhaps you are one and have issues about it. I can understand. Hornerites know who they are, and you know who you are. Perhaps those statements have a lot of "overlap" much like our lovely dinosaur friends here. It's your call dude.

They aren't arguing like lawyers, they are arguing like Scientists. The evidence isn't meant to be irrefutable. And it isnt based on an a posteriori conclusion to which the data is aligned to agree with.

They admit there are flaws with their conclusion but go on endorsing it anyway, in hopes that the flaws will not make the conclusion invalid. They admit some of the ontogenic changes they suggest for pachys are pretty extreme. Same with ceratopsids. And they still refuse to see any alternative as equally likely. If that's not lawyering, then that term is more applicable to Horner's followers than Horner himself. However, he does have knack for endorsing theories that have less and less credence as time goes on. That's the point behind my reference to the scavenging T.rex.

Can anyone say "escalation of commitment"?

even if you cant agree that toro and trike are the same, all large Trike skulls are still only young adult

Prove this. Even Horner himself admitted IN PRINT that defining that an "adult" animal is very difficult if you are going on fossils. Aside from fusion of vertebral elements and size, adulthood is tricky to gauge with large specimens.

Ultimately Toro = Trike is a falsifiable hypothesis, Toro and Trike are sympatric species is not.

Actually it is falsifiable. You falsify it by finding a "Toroceratops" that's just barely got fenestrae, has a squarish frill, and has shorter, more forward-curving horns. But hair-splitting aside, if your hypothesis is falsifiable, why are you so fanatically defending it? What if it's falsified tomorrow? Would all your mudslinging have been worth it?

Nima said...

BTW Chris, Chasmosaurine bodies are very similar, the only one with any significant variation is Anchiceratops, which in unusually compact and thickset. Hadrosaur bodies show two main morphotypes, other than that they're fairly consistend across genera. Iguanodontids have their own range of morphotypes. That has no bearing on my statements at all.

The "entire" head doesn't change, just the post orbital horn cores, which is just a continuing trend in the re absorption and deposition seen in younger stages, and squamosals and parietals, which again is just a continuing trend from younger stages.

So the radically different Torosaurus frill shape means nothing to you?

Actually there are a lot. Seriously, like a few hundred. The double curved brow horns that you claim exemplify adult Trikes, are the brow horns in transition from the juvinile posteriorly curved morph to the adult morphology of forward curvature.

Then show me an "adult trike" that has fenestrae or a very thin frill! When they are all over an inch thick, and rounded off, it's hard to prove a transition....


There is no partial Juvenile Torosaurus. Unless of course you would like to provide me with a reference. Until such is provided, its unsubstantiated gossip or worse.

Here's your "gossip"! Enjoy the humble pie.

Hunt, ReBecca K. and Thomas M. Lehman. 2008. Attributes of the ceratopsian dinosaur Torosaurus, and new material from the Javelina Formation (Maastrichtian) of Texas. Journal of Paleontology 82(6): 1127-1138.

There are juvenile specimens in the paper identified as T. utahensis. And there's also some adult material from the same site.

Why is it so difficult for people to understand that science is not about the truth, its about what is best supported by the current evidence.

Why, I might ask you ("alleged") Hornerites the same thing! I'm critiquing Horner's ideas, not claiming mine are absolute truth. Furthermore, if the "current evidence" is twisted to support a wrong conclusion, that's not science either. Just keep an open mind on that.

Nima said...

Nima, your rhetoric reads like you lifted it right out of the creationist mad libs book of arguments against evolution. You need to do better.

Actually I have debated plenty of creationists, their primary tactic is to get personal, LIE and put words in people's mouths, misquote scientists, slander, insult you, etc. I have done none of that, I'm not trying to do polemics or make you look stupid. Horner's not evil, I'm not personally offended by his theories, etc... I shouldn't have to say this, I thought it was pretty obvious that I was just factoring in the science, not personal feelings (if you read what I said earlier, it makes no difference to me personally how many ceratopsians there were in the Maastrichtian... life goes on).

I'm not making a blanket statement about ceratopsid ontogeny the way creationists make blanket statements about evolution. I'm just saying that I don't agree with a certain narrowly defined theory that only affects two genera anyway. Of course dinosaurs went through ontogenic changes. I just don't think that makes Torosaurus the same as Triceratops given what we know for sure.

Or, to reword it in your creationist paradigm "Of course I know evolution is real. I just don't think that this particular animal evolved from that particular animal based on the evidence we have."

See, it's a much more small-scope debate. I'm not in any way denying established general facts like evolution or ontogeny changes.


@ Df9465
I'm not sure what you mean about me being so "wrong" about Pentaceratops. All I said was that the horns curve forward, have grooves, etc. I didn't say all that much about Pentaceratops, in fact I only mentioned it in comparison to Torosaurus. The two are indeed closely related.

I have read quite a lot on Pentaceratops, the Horseshoe Canyon and Kirtland formations, etc. and what's wrong with my (albeit brief) Pentaceratops remarks? You don't have much of a point here (or an identity for that matter... with all due respect if you're a paleontologist, please use your real name and not some random numbers).

df9465 said...

@Zach: Triceratops frills are not all wave shaped or however you want to put it. Mostly they are pretty flat just like Torosaurus. Some taphonomically squashed specimens can be misshapen, but there is no issue with parietal shape regarding transition to Torosaurus. Toro frills do expand a bit laterally as part of the final growth change, but this is no big deal.

People are complaining about a lack of intermediates... the incipient fenestrae are present in all the trike skulls that we see. but they are on the underside (ventral surface) of the frill: the dorsal surface merely records an inconspicuous surface texture change: just the same as opening fenestrae in centrosaurines. The evidence is extremely strong.

@Nima: Pentaceratops: not known from the Horseshoe Canyon. Is only present in the Fruitland Fm & Kirtland Fm of New Mexico (even this can be debated). The Juvie material from colorado may or may not be Pentaceratops sp. because juveniles vary their morphology considerably from adult forms. This is one reason why mojoceratops is probably not a valid name.. or at least, not all the ascribed material can be placed in that genus.

Pentaceratops has never come out as the sister taxon to Torosaurus in any cladistic analysis that can recall. Toro is almost always recovered as sister taxon to triceratops. Take a look at Mojoceratops Eotriceratops descriptions, Dinosauria 2 chapter etc etc. sometimes (eg. Loewen & Sampson 2010) it comes out ina polytomy with eotriceratops etc, but never with pentaceratops. I don't know where you got that "fact".

df9465 said...

@Nima

"They admit some of the ontogenic changes they suggest for pachys are pretty extreme. Same with ceratopsids..."

So what if they're extreme? The size change from a hatchling to an adult is extreme, why would we not expect some "extreme" cranial changes? Did you look exactly the same as a baby as you do now? You don;t have a good argument here. I don;t believe it!" is not a testable scientific hypothesis.


"... And they still refuse to see any alternative as equally likely"

No, they entertain the other possibilities and suggest that ontogeny is the most liekly. what other alternativesdo you have? Diversity first is not a testable hypothesis.

"Scavenging t.rex"

Jack just says this to demonstrate that YOU don't know that an animal is an active predator just by saying so. What's the evidence? How can you "prove" it? how can you test if T.rex is an active predator?

"Then show me an "adult trike" that has fenestrae or a very thin frill! When they are all over an inch thick, and rounded off, it's hard to prove a transition...."


an adult trike with fenestrae is called "torosaurus". Frill thinning occurs ata number of points during triceratops ontogeny, mainly associate with later changes in the frill morphology and associated with textural change. It's a valid criticism that there isn;t a big data tabe and hundreds of photos of all the specimens in the study, but then, this is JVP and that sort of thing isn;t really possible here. Anyway, there will be follow up papers leaden with data and pictures.

"juvie toro from texas: hunt & lehman 2008"


Read the paper please. The juvie material form this site is not diagnostic cranial material and hence can only be ascribed "ceratopsidae sp." since all chasmosaurines have similar postcrania, right?

Glad I work on hadrosaurs said...

Quote from Nima: "The brow horns are proportionally a lot shorter than in any adult triceratops, and also feature a prominent groove on the outer side - a feature also found in Pentaceratops, but NOT Triceratops. "

Oh, damn, I'd better go put back all the Triceratops horns with grooves I collected from the Hell Creek last year. Sorry for my ignorance; I don't work on ceratopsians. I just assumed that when I was collecting 3 Triceratops skulls last summer, the grooves were normal Triceratops morphology. Thanks for showing me the light, I'd better go name them new taxa.

Seriously, though, if you get a chance to go to the Museum of the Rockies, go look at their row of Triceratops/Torosaurus skulls, all lined up in size order. The brow horns, squamosals, parietals, and epiossifications sure look like a nice smooth growth transition to me.

Another quote from Nima: "The frill is insanely thick, both in small and large individuals."

I've been tripping over Triceratops frill in the Hell Creek for 10 years now (the damn stuff is everywhere), and the frill thickness DOES vary by size/age. Certain ontogenetic stages have thicker frills than others. I'm sure Scannella could tell you all about it. He can probably tell you the ontogenetic age of a specimen just based on frill thickness. He can probably tell you a lot of things. Doesn't he have over 60 specimens, or something like that? How many specimens have you looked at?

Glad I work on hadrosaurs said...

@Nima&Zach Re: lack of transitional parietal fenetrae development

Please see Scannella and Horner 2010, Figure 1.

And yes, there are more specimens that show the thinning "scoop", but putting them all in may have cluttered the figure.

Jaime A. Headden said...

Just an insert here: Virtually all of the histological work done by Scannella and Horner on the Torosaurus and Triceratops samples are based on horn sections; these show an increase in vascularization, followed by an increase in resporbtion zones, then by a decrease in vascularization. The Torosaurus core used to sample the "large adult" model in the paper (among a few other specimens) is regarded by S&H as very short, and the authors affirm what Nima stated that Torosaurus horns seem to be on average shorter than Triceratops. They proclaim, based on their inference of age of the histological sections, that the horns are being resorbed. There are some reasons to contest this, the least of which is that a sexually selected or visually selected organ like the brow-horn should not tend to decrease in size, unless the age model was diminishing from maturity (senesence). It is inconsistent, in fact, with total biological knowledge of secondary sexual or display features that smaller is equated with older (save in mammals, when oldest are smaller/weakest than the mature).

The main issue with the chain S&H provide to assert this is that the authors provide little measure in how they determined the nature of the sampled taxa (knowing which are which taxon) from which the authors may test their theories. The primary distinguishing characteristics (parietal shape, presence of fenestrae, extreme thinness of the frill, no distinct epoccipitals, relative length or orientation of the brow horns, lack of a "step" in the proximal squamosal) are not always found in the samples, so a conglomerate among both taxa is made to try to "tease" a sample. Virtually ALL of the skulls collected by the MOR team (app.1 in S&H) are incomplete, and are likely to be missing at least one of the above features, but some listed specimens are missing between half and all of the relevant regions. It begs the question that when dealing with complete skulls, how can the authors be sure they are correctly sampling the taxa? S&H argue almost from the beginning of the paper that the taxa are synonymous, and go out to prove their case, and dismiss the various contradictions nearly out of hand (just as was done in the Pachycephalosaurus paper.

As Nima suggestsd (although I cannot agreew without seeing the data, one further sampling issue is that S&H are assuming that the Triceratops specimens they are working with are consistent morphologically and taxonomically (they do not, however, separate the horridus and prorsus samples, in case there IS a phylogenetic signal and means of discriminating their taxonomic lumping). This leads to a further issue, that it seems easier to regard species as valid, but not genera, as if there was a difference outside of Linnaean Systematics, or philosophical "kinds."

Sampling biases lead scientists astray, and may mislead people into thinking there is a valid signal when in fact they have not eliminated all possible, or even likely, contradictions. That S&H are preparing a paper on taxonomic distribution AFTER attempting to synonymize taxa (which, again, they fail at as they've not indicated what T. latus is synonymous with).

df9465 said...

Jaime said: "They proclaim... that the horns are being resorbed. There are some reasons to contest this, the least of which is that a sexually selected or visually selected organ ...should not tend to decrease in size... It is inconsistent... with total biological knowledge of secondary sexual or display features that smaller is equated with older".

Is it? Guess you haven't read about pachyrhinosaurus ontogeny, where the horncores get resorbed through to adults. Just more ignorant opinion then.

Most of jaime's remaining text is difficult to decipher but I think he is trying to say that incomplete skulls cannot be assigned to species with confidence. Really? no apomorphies? do you know how horridus differs from prorsus? through ontogeny? through time?

I think the "jaime knows best" tone of this posting is disrespectful... although not so bad as "nima knows everything because greg paul and bakker told me so" but still pretty snooty. To suggest that "sampling biases lead scientists astray" when this is probably the most heavily sampled study of a dinosaur taxon is a stupid thing to say, makes you look utterly ignorant. Of course, taxon morphology is 100% consistent when you have a sample size of 1.

We've been resampling for Triceratops in the Hell Creek, collecting more new Triceratops skulls than exist in the rest of the world put together (in the past couple weeks alone we have another 3). We have detailed strat data for most of these specimens. We found that T. horridus and T. prorsus are stratigraphically separated; something that would have been possible to observe before if other people had bothered to pay attention to strat.

It is tough to publish the synonomy of Torosaurus and Triceratops without the stratigraphic work, since the strat work does inform strongly on trike morphology through time, but this approach seemed to be the correct one. Torosaurus IS Triceratops. Those Toros found in the horridus zone, are probably horridus, those in prorsus zone, are T. prorsus. There are some extra details to be ironed out here, because we are dealing with 2 (evidently difficult to grasp) concept leaps at the same time.

BTW, in the main blog posting, it says Tatankaceratops had an unfenestrated frill; Ojoceratops too, hell.. even Eotriceratops. Any data on that? Seen the specimens? Even read the papers? Garbage. Stated like fact. Stated in ignorance.

All I see in these postings is a bunch of people who are (for whatever reason) really bitter at horner, and just don't want to 'believe' this paper. Well, come up with a valid test, because that's science. Or just keep making it all up.

Zach said...

Looking at all three papers right now, and you're right--none of them have complete parietals. I'll edit the text.

Christopher said...

In addition to Pachycepalosaurus, Centrosaurus, Styracosaurus, Pachyrhinosaurus, and Chasmosaurus belli all reabsorb their orbital horn cores away to nothing as they mature. Less than nothing even, in some cases they eventually become pits. Nothing in the mechanisms that S&H propose is new or radical.

Nima said...

@ df9465

Let's clarify something. Please try to show a bit more maturity here. Jaime is not attacking anyone, and the tome of his post was ANYTHING but snooty.

I think the "jaime knows best" tone of this posting is disrespectful... although not so bad as "nima knows everything because greg paul and bakker told me so" but still pretty snooty.

Wow. REAL MATURE. Is that the way a professional academic should act? Does Horner behave that way? I doubt it. Jaime's statements were impartial and objective. To say that they insinuate anything arrogant or disrespectful against you is your own negative distortion of things. Everyone is not out to get you, whoever you are. BTW where do you get such thin-skinned paranoid NONSENSE as "Nima knows everything because greg paul and bakker told me so"? Did I ever make such a statement? Didn't you get the part where I said I don't always agree with them like some fanatic acolyte? Or do you have "selective literacy" with these things?

I wasn't aware I knew everything... Nor was I aware that Bakker and Paul did... remember, I don't idolize them the way you do Horner. My point was I don't demonize anyone for not agreeing with them, though you apparently see nothing wrong with insulting the heck out of me and Jaime and anyone else who doesn't worship Horner. I wonder what Horner himself would have to say about such antics.

We've been resampling for Triceratops in the Hell Creek, collecting more new Triceratops skulls than exist in the rest of the world put together (in the past couple weeks alone we have another 3). We have detailed strat data for most of these specimens.

"WE"? So you're part of Horner's crew? Ahh yes, so there is a name behind the number. That's a major conflict of interest, considering you're pushing Horner's theories so emotionally. All the same, I'd advise being a bit more respectful of others, whether in academia or out. I'm sure you're aware the field doesn't benefit from vindictive quarrels.

To suggest that "sampling biases lead scientists astray" when this is probably the most heavily sampled study of a dinosaur taxon is a stupid thing to say, makes you look utterly ignorant. Of course, taxon morphology is 100% consistent when you have a sample size of 1.

Hehe so we're mentioning only one skull as evidence? Prove it. Never said that, did I?

I've read plenty of Horner's papers, and though it's undeniable he samples a huge amount of material, his writings tend to gloss over a lot of the inconsistencies in the evidence (and thus the holes in his argument). Don't forget, Horner's been pursuing this conclusion at whatever cost to credibility for several years now. He didn't just come to it yesterday after so many years. Science is not about choosing what to believe and picking evidence to support it - it's about figuring out what the evidence on its own indicates is the most true.

Every one of his papers on ontogeny of this or that group, has exactly the same premature conclusion regardless of what the evidence says (or more importantly, doesn't say). Too much guesswork, too little exploration of alternate hypotheses. Nor does he provide an explanation for why Torosaurus is so rare, while the "young adult" triceratopses are so common. Isn't the prime of adulthood the LEAST likely time for all of them to get eaten or mysteriously disappear?

Nima said...

BTW, in the main blog posting, it says Tatankaceratops had an unfenestrated frill; Ojoceratops too, hell.. even Eotriceratops. Any data on that? Seen the specimens? Even read the papers? Garbage. Stated like fact. Stated in ignorance.

Really? All in ignorance? Hehe a little tact wouldn't kill you my friend... Eotriceratops begs to differ:

http://4.bp.blogspot.com/_vdMpbAB0DRI/SSd6lHxiY5I/AAAAAAAAHJA/idVOhtlf0qo/s400/Eotriceratops+horned+dinosaur+ceratopsian+skull+fossil+museum+tyrrell.jpg

LOL that looks pretty unfenestrated to me!


All I see in these postings is a bunch of people who are (for whatever reason) really bitter at horner, and just don't want to 'believe' this paper. Well, come up with a valid test, because that's science. Or just keep making it all up.

Bitter? Not at all! We love Horner! If there was no Horner, why, life would just be dull! It would be as if Letterman and Leno both killed themselves...

But in all seriousness, nobody is "bitter" in mainstream Paleontology. That just clouds the progress of science and makes the field look bad. Rather, Hornerites, BANDits, SNAFUists, small-earth catastrophists, etc. are bitter. Because they simply can't see things any other way. They can't bring themselves to even acknowledge the very POSSIBILITY that their theories might be wrong.

Instead they bash anyone who disagrees as "ignorant, stupid, snooty, disrespectful", etc. and pretend everyone is persecuting them - does that seem familiar? Creationists and flat-earthers have also used this tactic, ever since the days of Darwin and Huxley. I strongly urge all the PROFESSIONALS out there (no names named, as per their choices of blogger ID's) to avoid these kinds of abusive rhetoric.

Christopher said...

Nima, seriously, please go read the Eotriceratops paper. Only two small pieces of the parietal was preserved. The largest at about 30cm across is from the anterior parietal midline located just behind the frontals, and preserves a portions of the superior temporal fenestra. The second piece is a small fragment of unspecified position, ie unknown. The Parietal of the model is entirely reconstructed based on the hypothesized close relationship to Triceratops. The parietal fragment is said to be quite thin, thinner than in Triceratops, this together with elongate reduced epoccipitals and forward directed orbital horn cores suggest an advanced ontogenic stage and so parietal fenestrae may well have been present. However, no bone histological analysis was performed on the specimen so whether it was as mature as specimens of Torosaurus or slightly less mature like AMNH 5116 is open to speculation at this point.

Jaime A. Headden said...

Denver wrote:

"Most of jaime's remaining text is difficult to decipher but I think he is trying to say that incomplete skulls cannot be assigned to species with confidence. Really? no apomorphies? do you know how horridus differs from prorsus? through ontogeny? through time?

I think the "jaime knows best" tone of this posting is disrespectful... "

I'd like to stress that Denver's argument of my disrespect is completely unfounded. If he's going to make this argument against me, he should back this up. I've not said anyone in this is _wrong_, yet it seems he has adequate reason but no fact to support this.

I also find the quote mining above to be an unfair, and unprofessional way of relating my argument, which was more complicated than saying "I disagree with Jack Horner." I don't.

I don't disagree with the material OR the conclusions of Horner and colleagues, and have said so before including on the DML on this topic. What I disagree with is the steps taken to get from A to B, which apparently diverges rather than sets itself up with a secure progression. That is, I disagree with HOW Horner et al. get from their datasets to their conclusions.

It also seems I am being lumped into a group of "anti-Horner" folks, some who may disagree with him in principle. I wouldn't, as a scientist. I am more concerned here in the process, rather than the result, and it seems that some feel Jack is more into conclusding data, which is it's own argument I won't touch. Denver's defense of Horner's scavenging hypothesis, repeated in various news bits for over two decades and two large, general-reader books, is problematic from a standpoint where we should be reasoning data by objective argument, especially given that Horner does not elaborate that he is trying "to demonstrate that YOU don't know that an animal is an active predator just by saying so." He's arguing a priori (conclusion before data), a similar sympton of what I was mentioning on the DML about the Pachycephalosaurus paper (one should note the sample size there is a lot smaller than in the chasmosaurine study we're dealing with more here).

We can take the work of Horner and colleagues in step to address issues, and I intend to just to discuss process and method on my own blog in due course. What I've said before were responses to various personae here, including Nima. Bringing the arguments made here about the peoiple involved (Jack, me, Nima, etc.) is POOR argumentation, and I'd think that some of the folks here would be beyond it, including you, Denver. It is, for lack of any other term, argumentum ad hominem. This includes Denver's accusation of my "jaime [sic] knows best" tone.

Nima said...

Indeed, Jaime. Such is the sad mark of a Hornerite.

Jaime A. Headden said...

On Eotriceratops xerinsularis:

With regards to the thinness of the parietal (at points): Wu et al. note that the parietal fragment adjoining the braincase, preserving portions of the supratemporal fossae, thin to about 1.5 cm (which is fairly thin), but their remark about being thinner than in Triceratops is not noted with any particular specimen or relative position; it is unclear if they mean only that section of the parietal.

The isolated, blocky element argued to be a section of the frill is about 3cm thick, and when compared to juvenile Triceratops (Scannella and Horner) the frill is typically thicker along the rims, but in adults it is apparently 2.5-3cm, or are much thinner (5mm) within the depressions on the ventral surface of the frill. So it is unclear what is meant by "thinner," especially when age is concerned.

Jaime A. Headden said...

I am concerned about one major issue involved in Scannella and Horner, but it has nothing to do with the meat of the paper (at least, not directly). The paper is appended by a table listing a large number of Triceratops skulls collected by the MOR project. Some of these are very incomplete (e.g., MOR 989 is a rostral and a nasal horn, while MOR 2937 is a maxilla) which, to my knowledge, lack features explicitly diagnostic of any species of Triceratops so far argued as valid. I haven't examined the material, of course, so I can't question this premise, but for the most part most workers tend to agree that of cranial material, the squamosal and the parietal are the second to the most (respectively) important bones when diagnosing ceratopsids; among some ceratopsids, it is the ONLY way to discriminate taxa (see comments in Longrich, 2010 on Mojoceratops). On top of this, adult specimens are almost certainly considered the primary means by which taxa should be diagnosed.

When collecting material in the Hell Creek, even considering the premise of multitaxic recovery to be unlikely, are the specimens actually just referred to Triceratops or a species thereof, or the inferrence in the table a result of the work in the paper wherein the authors simply argue all Hell Creek ceratopsians are Triceratops (or a species thereof)?

I only ask because recent discussion on diagnostic material has required associative and adult material to infer diagnostic material, while even growth series in centrosaurines provide that they are virtually indistinguishable from one another (as several are known; see Currie et al. on Pachyrhinosaurus lakustai). Also note that centrosaurine ceratopsid growth series are almost exclusively made up of bonebeds of associated specimens, from juveniles to subadults, and occassionally an apparent adult. These bonebeds would almost certainly set the bar pretty high for inferring a consistent growth series, especially if they were specifically consistent and distinguishable (can the authors distinguish a juvenile to either Triceratops prorsus or Triceratops horridus without using stratigraphy?).

Once again, my "tone" is not meant to cast Horner and colleagues in any bad light, or discount their conclusions.

df9465 said...

There really isn't much more to say about Nima, since his posts are little more than uninformed sniping with little sniggers (LOL, hehehe, etc). Go and read some papers Nima, then come back, maybe. Actually don't bother.

I think the tone of the posts WAS disrespectful, but I'm prepared to accept that it wasn't intentional (on Jaime's behalf). Scannella & Horner considered many possibilities in their research, and synonomy was the most likely. Still, you make the point about it being preferable if specimens came from a single bonebed. Triceratops bonebeds have been known or ?100? years, just buried in the literature. We have one site that records 3 specimens of different growth stages (in addition to the Burpee site), and the publication on that is in review (so I believe). Still, there are limits to what you can do with 3-specimen bone beds, and we're not likely to get 1000 specimen bonebeds anytime soon. This is why we measure the strat. I can place almost all our specimens within abotu a metre in section, accounting for variations in the strat due to sequence boundaries. It is precisely because we have done this that we can account for variation due to stratigraphic position.

In many ways, the story of Triceratops' evolution is more complex than we thought, but from another perspective it is much more simple. Part of my presentation at SVP will be about long term trends in chasmosaurine evolution. We can measure these using high-resolution stratigraphy and ontogenetic analysis.

Without proper understanding of ontogeny and stratigraphy, taxa are difficult to define reliably. Mojoceratops may be a genuine taxon, but I suspect at least one or two of the assigned (or susupected) specimens may prove to be ontogenetic and/or stratigraphic morphs that are not actually the same taxon as the type. It's a more complex (but again, also more simple) story.

We haven't found any evidence to suggest that more than one chasmosaurine is present in the Hell Creek formation, at any given point in time. there are parsimony and statistical reasons why divesity is unlikely, but you;re going to have to wait for the papers.

It might be sad to some folk to see dino diversity being lowered across the board, through syonomy.. but this doesn;t actually change the situation regarding extinction etc. you're merely seeing 10 species instead of 20 at the KT. this approach does however increase our understanding of ecosystems and paleobiology.

Recently, Jack said that he thought synonomy would mean losing about 1/3 of dinosaur taxa. I think that this is an underestimate. Time will tell.

Nima said...

There really isn't much more to say about Nima, since his posts are little more than uninformed sniping with little sniggers (LOL, hehehe, etc). Go and read some papers Nima, then come back, maybe. Actually don't bother.

I've read plenty of papers, and I don't assume that everyone who disagrees with me hasn't read them; both from Horner and his opponents. The field is far more diverse than just one opinion. I'm not your enemy; apparently peer-review is. It's not simply a matter of bad luck that Horner's views haven't gained wide acceptance. Ultimately regardless of which papers you find acceptable, it's the peer-review of established professionals that will find you valid or invalid.

And I'm not the first to point out that Horner's a priori methods have cost him a lot of credibility before. Don't dismiss me so rashly unless you're ready to dismiss the field, since most PhD's also do not accept Horner's conclusions and methods for a whole range of issues (and I can assure you it has nothing to do with "uninformed sniping" or "snooty bitterness").

Returning back to the main point, what will you do if it turns out that Torosaurus and Triceratops really are separate genera? Lets say a herd of Toros is found, and the juveniles have fenestrae in their frills. Would you be humble enough to admit it? I know I actually would, if they turned out to be the same genus.

The mark of a truly credible scientist is being up front about the evidence even when it doesn't support your hypothesis. If you read papers from Bakker, Paul, and about 99% of the paleontologists out there, you find cases where they are forced to modify or even discard their original hypothesis as new things turn up. In other words they are not too proud to admit when they mde a mistake. Horner's papers show many different unique insights and some credible arguments, but there is also a lot of arm-waving and a great deal more reluctance to modify or alter the original hypothesis when the evidence doesn't support it. Furthermore, when doing a study with such a large sample size, it's not even a good idea to formulate a definite hypothesis in advance. It's not an empirical experiment in the traditional sense, there's really nothing solid to be falsified yet! To avoid a biased conclusion, it makes sense to crunch the data and then look for a theory. Deduction rather than induction, and so on.

Nima said...

I could say for example (not that I would ever want to) that Diplodocus is a juvenile or young adult Barosaurus, that could be my "hypothesis" and after looking at fossil samples I could say that even though the shape of many of the bones is different, different positions of fossae, etc., that's all unimportant because "probably" the juveniles went through a lot of ontogenic changes with neck length, adding neck vertebrae (!), and spinal morphology, so "anything" is possible, and both animals are found in the same formations, same stratigraphic age, etc....

It's impossible to test and falsify such a hypothesis, since any different between the two genera can simply be put down to ontogenic changes, there's no transition stage because the changes happened too quick (and if mysteriously there were no studies done on the ages of the specimens at death, I could also tell everyone who disagrees to shove it and "go read some papers" since "there IS and ALWAYS WILL BE only one diplodocid species in the Morrison formation", heck let's discard Apatosaurus and Supersaurus too, they're probably just other ontogenic stages after all!)...

Crazy, right? I'd be laughed at. And I doubt too many scientists will be willing to stake their academic reputation on advancing such an untestable, un-falsifiable pseudo-hypothesis. It's OBVIOUSLY bogus. You couldn't pay me enough to believe such an anti-scientific theory that uses ontogeny as an excuse to simply ignore morphological differences wholesale. Now step back and think about that for a second. That is exactly the same way a great deal of the Hornerites' arguments appear to non-Hornerites. Lumpery at any cost by any means necessary of two genera in the same locale, one far rarer than the other, both of similar size and roughly similar appearance, being lumped together as growth stages, an argument to disjointed in its very nature to be falsifiable, and nobody has a right to disagree because "my sample is the biggest and hence I am no longer a fallible human being like the rest of you, and anything I say must be correct".

Not exactly the strongest foundation for good research, is it? Now keep in mind, a lot of what Horner says isn't as simplistic or fanatical as what many of his followers say. The real problem is not with Horner per se... after all he will continue to study what he wants and publish whatever conclusion he wants, within the conventions of peer review and the academic process. Rather, it's his die-hard groupies that need to be reminded that no researcher is "always right" and of what is and isn't science (and what is and isn't proper academic etiquette for a scientist to use in a debate).

Nima said...

As for losing 1/3 of dinosaur taxa.... I'm actually not opposed to this notion, since probably MORE than 1/3 are simply names given to a single tooth or a single bone, and are not diagnostic at all.

However, in terms of truly diagnostic taxa from which a good amount of material is known (i.e. more than 30%) I doubt there's any credible way to lump them together to lose 1/3 of THEIR diversity.

In fact, these days as more research is done, it's taxonomic splitting, not lumping, that is the general rule. There used to be 3 accepted species of Brachiosaurus, now they are all classed as separate genera. Rebbachisaurus has been split into two genera. "Oviraptor" is now Oviraptor and Citipati. Much of the material referred to obscure giant titanosaurs like Argyrosaurus and Antarctosaurus probably is from some other genus. There's even debate over the taxonomic integrity of T. rex among some pretty big names in paleontology, including Bakker (though I am not in favor of splitting T. rex). Albertosaurus has once again been split into Albertosaurus and Gorgosaurus, Pelorosaurus is almost certainly fit for splitting into as many as six different genera, and the list goes on.

Not that I'm a big fan of either splitting or lumping... I prefer a middle way that's equally critical and scrutinizing of both. (And in principle I do accept that most "species" of Triceratops were probably just growth stages). It's just that the evidence currently favors splitting many established taxa across the board (though others that are not so diagnostic probably should be eliminated altogether).

df9465 said...

More inane posting from captain caps-lock.

"what will you do if it turns out that Torosaurus and Triceratops really are separate genera? ...Would you be humble enough to admit it? I know I actually would, if they turned out to be the same genus"

Of course. Are you "humble enough to admit" that your indepth research on eotriceratops frill morphology consisted of a google image search which turned up a reconstruction of a complete frill, rather than actually reading the paper that described how little there actually was. Lord alone knows where you got your data on Pentaceratops, that was wrong too.

We're still actively seeking more specimens in order to test the hypotheses presented in this and forthcoming papers. Today we collected a 1/2 to 2/3 grown trike frill, and tomorrow we will continue work on another 2/3 size frill. If we were only interested in being right, we'd not collect any more now would we? they'd threaten our precious hypothesis.

Everyone is wrong from time to time. Some more often than others (your postings spring to mind).

Jaime A. Headden said...

Long reply. Stop me if I'm going too fast; I make a point of repeating myself a few times with "important" statements.

Denver wrote:

"Scannella & Horner considered many possibilities in their research, and synonomy was the most likely."

This is relevant to TWO of my contentions. Synonymy in the first case is NOT the most likely, but we'll get to a reason why this is the case a bit lower. The second is that the authors synonymize NOTHING. S&H argue that Torosaurus and Triceratops are synonymous, and argue only two valid species. They do NOT indicate to which species the holotype of Torosaurus latus belongs to. If it were it ambiguous to which species the taxon belongs, then S&H leave themselves open to an additional hole in their argument because latus may be valid, even if subsumed. They also refuse to admit the contradiction of Hunt and Lehman's revised diagnosis (citing the paper, but ignoring the restating of Sullivan et al and Farke's own restatement), which argues that Torosaurus latus may be diagnosed by a thickened medial margin of the squamosal, absent in Triceratops horridus or prorsus (but again, the remainder of this argument is below).

"Still, you make the point about it being preferable if specimens came from a single bonebed. Triceratops bonebeds have been known or ?100? years, just buried in the literature. We have one site that records 3 specimens of different growth stages (in addition to the Burpee site), and the publication on that is in review (so I believe). Still, there are limits to what you can do with 3-specimen bone beds, and we're not likely to get 1000 specimen bonebeds anytime soon. This is why we measure the strat. I can place almost all our specimens within abotu a metre in section, accounting for variations in the strat due to sequence boundaries. It is precisely because we have done this that we can account for variation due to stratigraphic position."

Would it have been a little too much to ask for Scannella and Horner to have gotten their ducks in a row before asserting that synonymy is present? I.e., S&H note that stratigraphic separation of the taxa may be relevant to the analysis. But ... they leave that for another paper, whereas it may have helped concretely assert taxonomic assignment and differentiation (the premise of the current paper).

"We can measure these using high-resolution stratigraphy and ontogenetic analysis."

As I stated, if the verifiable ontogenetic analysis, instead of a priori assumptions that all taxa in the Hell Creek are a single genus, thus affirming that any ontogenetic stage belongs to that taxon. Or that stratigraphy may play a role in diverting evolution of specific ontogenetic features (see centrosaurine evolution, which is different than chasmosaurine evolution, especially in the early maturity stages, such as when the nasal region develops into a roughened structure rather than a horn).

"Without proper understanding of ontogeny and stratigraphy, taxa are difficult to define reliably. Mojoceratops may be a genuine taxon, but I suspect at least one or two of the assigned (or susupected) specimens may prove to be ontogenetic and/or stratigraphic morphs that are not actually the same taxon as the type. It's a more complex (but again, also more simple) story."

See above. It seems odd that you wouldn't synonymize the morphologies from the same formation into a single taxon, or assume it could be ontogenetic variation, when all the specimens are constrained to two levels across two formations, which is less than the range in Triceratops alone, much less Chasmosaurus.

Jaime A. Headden said...

Part two of reply:

"We haven't found any evidence to suggest that more than one chasmosaurine is present in the Hell Creek formation, at any given point in time. there are parsimony and statistical reasons why divesity is unlikely, but you;re going to have to wait for the papers."

Here's where we find ourselves running into an issue that has been criticized in the past, and in print. Biostratigraphy is horribly prone to identification bias, an argument that has been used by Lehman and Williamson (and others) against the practice of Lucas et al. in various works. Arguing a priori that a taxon can only be taxon A, because the authors see other specimens in said level are taxon A, allows them to confirm their premise. This is also a confirmation bias. If we assume a priori that there's only one chasmosaurine in the Hell Creek, then any specimen we find will be said taxon. Is that logical? No. S&H show this may be incorrect when they affirm the presence of two chasmosaurines in the Hell Creek: Triceratops horridus AND Triceratops prorsus. This is an example of assuming a "genus" is somehow different than a contained species, especially if it's monotypic. The authors seem (again, SEEM) to be assuming that in their premise that taxic diversity in the Hell Creek is so low, and they do not see two different taxa, no such taxa exist (and they are wrong, as seen above).

This makes me make one of my larger points on this topic, and the reason why specific referral is required to affirm the premise, which the paper does not address: Two which species does Torosaurus latus belong? If it does not actually correspond to either horridus or prorsus, but can be differentiated from them, then Torosaurus latus as a species is valid, even if it belongs to Triceratops, as Triceratops latus; if Torosaurus latus cannot be differentiated from any of those species, then the taxon is ambiguous, it's likely a nomen dubium, and the taxon should not be referred at all to Triceratops (because it cannot be referred to a species). In these cases, Torosaurus latus may belong to the same animals as Triceratops horridus or prorsus, but it is not indicated which of them it applies.

Jaime A. Headden said...

And finally:

Horner made a similar argument in H&G's referral of all pachycephalosaurine Hell Creek material to a single species, without considering taxic differentiation can be below a level contained by Pachycephalosaurus itself (i.e., one could have a Pachycephalosaurus spinifer). This was even contested by comparative study of growth in Stegoceras, when involving only dome shape, which is apparent in Pachycephalosaurus only as long as Pachycephalosaurus reinheimeri is considered exemplary; if it isn't, it is only because Stygimoloch spinifer is considered as a synonym of Pachycephalosaurus wyomingensis, in which case we have another example of confirmation bias supporting the premise of a narrow dome expanding into a broad dome, instead of a low, broad dome rising into a high, broad dome (as in Stegoceras validum, accepted by H&G to be a confirmed ontogenetic series).

So ... in this contesting of the paper's process, even if their conclusion is correct, the authors add several leaps of logic, including assuming 1) that all material in the formation is a single taxon [only if that taxon is a "genus"], 2) that the ontogenetic series corresponds to said taxon and not to say, a finer or broader grouping, 3) that Torosaurus latus may include some, but not all of these specimens. Moreover, they even note that some specimens, such as AMNH 5116 and the ANSP specimen (from the Hell Creek/equivalent) are very different (mature adults at subadult size), but reject any premise that this may impact their theory that it is more parsimonious to assume one taxon (which as argued above is more a matter of scale).

I can go into an argument where it seems Horner is arguing "genus" actually means something, as many biostrat guys also seem to suggest, rather than being just a name for a level of taxonomic inclusiveness. This might even lead into an argument where such an issue with relation to diversity claims reflects arguments of philosophical "kinds," but I won't. I really don't care that Torosaurus could be subsumed into Triceratops, but the authors have made NO such case on a systematic level, and their use of a systematic section in this and the Horner and Goodwin paper appear to be after-effects of the assumption of synonymy.

df9465 said...

On genera: we rally don't care whether you use genus or species. The species is the only valid evolutionary unit anyway.

You don;t explain why synonomy is not the most likely. If you think that Torosaurus is tuly a separate genus, you are really saying "in my opinion, fenestrae in the frill are just too big of a difference or them to be the same genus". That is just opinion, not a testable hypothesis. I think that the other cranial changes through Triceratops ontogeny (brow horns, skul elongation etc etc) are rather more severe than a thin patch of frill finally getting fenestrated.

It would be nice to have histologic backup from cutting limb bones, but there aren;t many torosaurus limbs that have been collected associated with diagnostic skulls (I think there are 2), so it took time to secure specimens. Wait for the paper.

Don't keep stating that we "assume" that there is only one kind of chasmosaurine at any given point. This is not true and misrepresents our research and methods, and I personally take some offence at the suggestion. This view has come from careful analysis of diagnostic material. It is not an a priori assumption, it is a hypothesis that is constantly tested each time we collect another specimen. Currently no specimesn have been collected that would alter this view.

Hunt and Lehman mention the squamosal bar as a potential apomorphy, but it is present in Triceratops. maybe not all Triceratops specimens, but then, it is a character that vaies onotogenetically. T. uthaensis is no problem to this synonomy.

i have no idea what you're trying to say about Mojoceratops. Seriously, you have got to write more clearly.

Ontogeny happens. Anagenesis happens. both are easily testable. Diversity first is not.

Jaime A. Headden said...

Denver, I will put this into secure terms:

S&H argue that Torosaurus IS (i.e., is synonymous with) Triceratops. This means they synonymize them. They further regard only TWO valid species, horridus and prorsus. This then assumes they regard latus as a synonym of one of these. The only other option here is that latus is regarded as a nomen dubium and is placed within Triceratops as a doubtful taxon, but this is not stated in the paper. The authors argue instead they are "synonymous."

So, we have a small quandary: If the authors do _not_ synonymize latus with either horridus or prorsus, as implied in their systematic section, then they must assume that latus belongs to Triceratops, but is valid on its own regard (but that is clearly not what they say), and would be a third valid species.

Otherwise, the authors MUST consider latus to be synonymous with either horridus or prorsus.

One cannot synonymize Torosaurus with Triceratops, and leave latus in a fog somewhere yet also argue it is synonymous with ... something. Further, you cannot synonymize a species with a genus.

So the question that was asked since SVP was: If they are synonymous, to which species if Torosaurus latus referred?

PS: I still haven't gotten an answer to my question as to how specimens were referred taqxonomically on recovery or accessioning in the beginning, as this directly impacts the statement that the label doesn't matter (I disagree; it does when the authors are for taxic reduction).

df9465 said...

Agreed; horridus or prorsus is not specified in the paper, but this is because some Torosaurus will be horridus, and some prorsus, and some inbetween... this will be dealt with in a later paper.

On determining specimens. if you have the right lements exposed in the quarry, then you can tell what species a specimen is while it is still in the field. The majority of specimens are this way. In his talk, john uses an example of a Triceratops that was preserved upside down, so we couldn;t see the relevant morphology until it was back in the lab and prepped. We made a prediction about which species it would be (based on its position in section), and that turned out correct. If you only have a rostral, or a dentary, then yeah, you can't tell the species.. at that point you can infer that they are horridus or prorsus depending on the strat position, but you couldn't know for sure.

The only reason we can do this is because we have good understanding of the ontogeny of Triceratops.

df9465 said...

ah, and I will correct myself from before. The squamosal bar is a prominent thickening of the squamosal along the suture with the parietal. It is a result of extreme thinning of the squamosal, but the bar itself is only seen in Torosaurus-morphs. Thinning of the squamosal is seen in toro and earlier onotogetic morphs of triceratops, and sometimes it thins so much that it is perforated, as in "Diceratops", Pentaceratops "fenestratus", and a bunch other specimens probably. Squamosal thinning would seem to be a fairly common ontogenetic feature in chasmosaurines.

there are reasons why T.utahensis is different from other Toro's. this is part of my SVP talk.

Jaime A. Headden said...

I should have done this before, but I've now codified a portion of my thoughts on my blog, here. This is only the first part. Posting three-part segments of a blog reply seems ... a waste and inelegant.

Hikaru said...

@ df9465:
There is evidence that directly contradicts Horner's claim that Tyrannosaurus rex is a scavenger. A hadrosaur tail vertebrae Ken Carpenter's fossil collection have bite marks of T. rex, and those bite marks have signs of partial healing. Also, the left sqamosal region of A Triceratops' crest and left brow horn discovered by John Happ had also been bitten by a T.rex and those too have signs of healing. This is not to say that Tyrannosaurus rex had not scavenged for food since all known vertebrate carnivores also engage in scavenging, but to say T. rex is incapable of hunting is fully absurd.

Here is the link of those instances: (http://books.google.com.ph/books?id=5WH9RnfKco4C&pg=PA327&lpg=PA327&dq=healed+bite+marks+of+T.rex+on+Triceratops+horn%28Tyrannosaurus+rex.+the+Tyrrant+King%29&source=bl&ots=05bJYXYNPw&sig=lnuPHmg10EHqsA-qoQeBDUSm1JA&hl=en&ei=OERWTNiZJJKWsgPmhqHaAg&sa=X&oi=book_result&ct=result&resnum=6&ved=0CC4Q6AEwBQ#v=onepage&q&f=false); (http://www.mnhn.ul.pt/geologia/gaia/9.pdf).

Hikaru said...

@ Jaime, Nima, and Zach:
Ohayo/ Oyasumi nasai, minna:

As what had been mentioned in an earlier blog, the post-cranial skeleton should also be studied. Dr. T. Holtz Jr. had also suggested this as a means of independent test. (http://blogs.smithsonianmag.com/dinosaur/2010/07/22/new-study-says-torosaurustriceratops/).

Hikaru said...

@ Nima and Jamie:

Ohayo/ Oyasumi nasai, minna:

I would have to agree with you in your claim that Horner's tendency to use a priori methods is what ruins his credibility. As I have said in my first blog, his claim that Tyrannosaurus rex was incapable of hunting had been disproven by Happ and Carpenter based on Triceratops's bitten crest and Edmontosaurus bitten tail, respectively. I wouldn't even be surprised if his claim that Torosaurus is the same genus of Triceratops is falsified.

Hikaru said...

@ df9465:
Actually, for Triceratops, there is just one bonebed currently known. Why don't you read the paper on this topic:

Mathews, J. C., Brusatte, S. L., Williams, S. A., & Henderson, M. D. (2009). The first Triceratops bonebed and its implications for gregarious behavior Journal of Vertebrate Paleontology, 29 (1), 286-290

Aside from that, A. Farke had also once said that there were portions of the Triceratops skull in AMNH display that had been recast. It MAY possibly be a subadult Torosaurus that had been mis-assigned as a Triceratops. But again, I would wait for the paper in which an EFS of Triceratops and Torosaurus post-cranium would have been performed before making a conclusion.

df9465 said...

there was brief mention of a multi-specimen triceratops bonebed in hatcher et al. It wasn't thoroughly described. The matthews et al paper was the first thoroughly described bonebed. I was a reviewer on that paper by the way.

Further papers on Triceratops are forthcoming from this project. People who go to professional meetings know what to expect.

You should look again at the edmonto & Happ papers. Neither has any evidence of biting (ie. broken tooth piece), just circumstantial marks that could have been produced a variety of ways. Neither is evidence of direct predation. I don;t necessarily disagree that Tyrannosaurs were active predators, but the point about how difficult it is to actually prove it remains valid..

Jaime A. Headden said...

Denver wrote:

"You should look again at the edmonto & Happ papers. Neither has any evidence of biting (ie. broken tooth piece), just circumstantial marks that could have been produced a variety of ways. "

You've just overturned so much paleobiological inference, that it is no longer possible to infer that the Taung child was predated upon, regardless of the huge holes in its cranium.

The presence or absence of a portion of a tooth is not required to infer a mark is made by a tooth, just as the absence of a foot in an ichnite does not invalidate the identification of it as a footprint, especially when gouges (such as in bones scored by apparent Majungasaurusd teeth) share characteristics with tooth gouges, and little else. None of this, of course, indicates the animal was alive for a time after the mark was made, of course, save for healing traces or reorganization of the bone around the mark (as in the Edmontosaurus trace).

As Carpenter wrote on Edmontosaurus, circumstantial data can overwhelm by the amount of it any contradictory data on how the break occurred; this is true for the Triceratops hip marks, etc.

Trish said...

Just like to warn everyone that the mainstream news has just caught wind of this. Their reporting on it is... pretty much what you'd expect. (Enter that one "wallbanger" .gif I have here. This one's typical: http://www.dailymail.co.uk/sciencetech/article-1299666/Triceratops-really-existed.html Read the headline and then, buried deep in the pile of confusion: "All Torosauruses will be reclassified as Triceratops.")

Hikaru said...

@ Jamie/df9465:

The bitten portions of the Triceratops I was referring to were the left brown horn and the squamosal region of the crest. As I have said before, both those regions also show signs of healing and the shape of the bite marks on the left brown horn is consistent with that of a T. rex's tooth. I have read the paper about Happ's find. The same is true for Carpenter's Edmontosaurus skeleton. At the time that Edmontosaurus lived, the only carnivore tall enough to inflict bite that high along the herbivore's tail is Tyrannosaurus rex. Those cannot be claimed as merely circumstantial evidence; hence, inescapable conclusion: Tyrannosaurus rex also hunted from time to time.

df9465 said...

Happ (2008): given that the horn is pathological, it would not be unusual to find pits. These are typically associated with exostosis and/or injury, and are often sites of infected bone. Plus, the horn is remodelling anyway, so some sort of development anomaly might also be common (also e.g. squamosal fenetrae). OR they could be genuine t-rex bite marks.

Carpenter (1998): Pathological neural spines are common in hadrosaurs and other ornithopods, especially dorsal and caudal regions. The cause of these pathologies is not yet known. Last summer we collected a tail from an edmontosaurus with around 22 caudals (15 articulated) all with pathologies like those seen in the Denver specimen. I've seen more examples in Iguanodon from the UK (and still others in museum collections). It's equally plausible that such pathologies are due to other causes: trampling? maybe mating? biomechanical loading? or just plain disease?

Both Happ and Carpenter cases are equivocal unless you have a bit of tooth embedded into the bone at the site of rehealing. Tooth marks, ie. scratches, are a different case, since you can see where the periosteum of the bone has been scored etc by tooth use. I wrote a paper on this (Fowler & Sullivan, 2006).

http://www.robertmsullivanphd.com/uploads/120_Fowler_and_Sullivan__2006__-Toothmarks.pdf

If you can find scratch marks with partial healing, then you are on your way to demonstrating active predation, but this hasn't been found yet.

I don't have an issue with T. rex being a hunter: I suspect it probably was; but proving it is another case. That's the whole point about why Jack states that it was a scavenger. you might find it maddening that you do not have evidence that falsifies this view.. presumably one day it will turn up, but it hasn't yet.

df9465 said...

Happ 2008: the squamosal presents a potentially more compelling case, but again, you;re still just dealing with a couple scratch marks that show healing. Farke et al. 2009 published on frill pathologies, noted that they are commonplace in chasmosaurines, and suggested it may be from horn locking combat (ie. within triceratops). While there are some reasons to doubt the horn locking hypothesis, a couple scratches on the squamosal might have been formed from another triceratops: frill on frill contact, or even a kick from some claws? Toothmarks and trample marks are often confused.

And anyway... if it turns out there is evidence of T. rex predation, then great! I'm happy!

Hikaru said...

@ df9465:

About the argument that Tyrannosaurus rex being a scavenger, I don't disagree with that. Come to think of it, all known kinds of vertebrate carnivores are a mixture of hunter and scavenger. But the point is, the features of the injuries(i.e. shape, distribution of marks) is just too consistent to be caused by bone resorption, microbial action, or horn thrusts(if two Triceratops would lock horns with each other and one of broke its left brow horn, that would not leave such marks on the left brown horn). Of course, one couldn't expect that a hunting T. rex would always leave behind a piece of its tooth embedded on a bitten region of an prey species that survived the attack, and even if a piece(i.e. tooth crown) is left behind, that piece may not be fossilized. I think what should be done is determine how Tyrannosaurus rex acquired most of its meals.

By the way, if you are performing an EFS on the Triceratops and Torosaurus post-cranial skeleton (as suggested by Dr. Holtz), may I request to be sent a copy after the analysis is done? I greatly appreciate reading papers about dinosaurian biology.

Jaime A. Headden said...

Denver:

The specific set of caudal marks are formed in what are argued to be a half-circle arc that is consistent in size to the premaxillary/anterior maxillary semicircular bite of a tyrannosaur, or so Carpenter argues. Does this compare with your apparent contradictory, and unpublished, data? Carpenter even details the contradictions (stepping, tail bending, etc.) that would damage the tail, which are not explained by lack of damage to any other part of that region of the tail). You claim pathology, but Carpenter reflects that the bite mark IS a pathologic trace in and of itself, so this is not a dismissal.

I was mistaken in referring to the Triceratops trace as a hip one.

Note that any animal that is bitten, lives, etc., cannot ever be proven to have been bitten without teeth (and even with teeth) imbedded in the wound, as the tooth can be circumstantial to the bite itself (via another bite), in which case one can infer that a bite trace and a biter can never be linked. Carpenter attempted to assert that, if the edmontosaur were standing, the only animal that could get to the top of its tail was a Tyrannosaurus.

Oh, and the irony: Horner has only published his hypothesis in popular books, aimed at lay readers, or at kids. He has never formally explicated his hypothesis (i.e., set up criteria by which it could be disproven), but has repeated it to kids, during the Egg Mountain excursions, and in his books, on TV, etc., even after being told he'd never published his theory. This seems a tad irresponsible of him to then turn to others and claim that he's doing this to point out to scientists (whom were not his audience) the faults of creating hypotheses without supporting data. It's also hypocritical.

Trying to "prove" Tyrannosaurus was a predator then seems to be diversionary of us, as the argument had become so prevalent several workers went out of their way to demonstrate pathologies diagnostic of puncture wounds, scorings, and shape-based bone removal consistent with bite marks in order to address a non-formalized hypothesis. Seriously?

Jerrold said...

Does this mean that all the Triceratops specimens currently known are sexually immature? That seems to be the implication. If they did not reproduce at the Triceratops stage, the final frill change would presumably have been driven by the necessity to find a mate during the Torosaurus stage. If they did reproduce at the Triceratops stage, then why would the frill continue to change after the reproductive years were over?

And why would there be such an enormous disparity between numerous subadult specimens and few adults? Is there anything comparable in other dinosaur species?