The following blog post is about "Toroceratops." I've taken heat for my views on "Toroceratops" in the past, and I expect this time to be no different. You should know that it is EXTREMELY ranty and, at times, kind of pissed off. I am FULLY aware that my frothing guile may have caused me to misunderstand or misconstrue certain things. If that's the case, please correct me in the comments. This rant is not so much an actual, serious rebuttal of "Toroceratops" as much as it is my personal problems with how the discussion is being carried out.
THAT SAID, please continue.
As Quilong said over on his blog, the "Toroceratops" controversy continues, but in an excellent way: each new paper that comes out not only attempts to rebut the previous one, but also provides priceless new information on Triceratops and Torosaurus in the meantime. Perhaps the best part is that this back-and-forth is available (mostly) freely to the public thanks to that bastion of our Shiny Digital Future, PLoS One:
The initial paper, unfortunately published in JVP;
Andrew Farke's redescription of Nedoceratops;
Scannella & Horner's reassertion that Nedoceratops is a transitional Trike;
Longrich & Field's attempt to suss out age based on skull suture fusion.
"Epioccipitals? Please. We've found Trike skulls with asymmetrical numbers of epioccipitals. There is an insane amount of variation there. Orbital horn core angle? Dude, are you kidding me? Nasal horn size? Well, Nedoceratops might be clear at one end of the spectrum, but let me tell you--there's a spectrum. I've seen it!
"Skull suture fusion? Allow me to break up the party: we've got Triceratops skulls that are from big adults who don't have all their skull bones fused up. And the opposite, too: small Triceratops skulls with fused skull sutures! See what I did there? I blew your effing mind. Tatankaceratops, baby. Think about it."
Now, look: I am fully ready to accept that there are some freaking wierdos out there, but you haven't shown your work. You have given me one transitional morph: Nedoceratops--one of the most controversial ceratopsid skulls in history. It has three names. Out of hundreds of Triceratops skulls, this is the only one you can point to that has parietal fenestrae? And even then, these particular fenestrae are in wierd places that don't match up with Torosaurus really at all. And it's got that irritating squamosal fenestra that just doesn't look healthy.
Please dig through your massive collection of Triceratops skulls (over 100, apparently, in Montana alone!) and pull out another contender. I know you've got one. Don't hold out on us.
Oh, and the epioccipital thing? You'd like to think that the reason Torosaurus has more epioccipitals than Triceratops is due to two factors: epioccipital count is apparently extremely variable in that basement full of Triceratops skulls you have (thus influencing how many the eventual Torosaurus morph would have); maybe--now work with me here--the epioccipitals in Triceratops split, like an amoeba, into two distinct epioccipitals. As evidence, you're point me toward...
The episquamosal of MOR 2975. The point has been worn down, which you folks suggest is because of "splitting." Yes, good. That's the most likely answer. Has epiocciptal splitting been demonstrated in any other ceratopsid? Hell, the fact that you can't find more than one potential example of epioccipital splitting--what with your baseball stadium filled with Triceratops skulls--is just a hair troubling.
In fact, remind me which ceratopsid currently known from a good growth series (like Pachyrhinosaurus, Centrosaurus, or Ajugaceratops) demonstrates such a spectacular morphological change late in life. Now Pachyrhinosaurus, man, he goes through one helluva puberty phase. But it happens surprisingly early, and at a constant rate. And it seems like lil' Ajugaceratops provides a damn good basis for adult Ajugaceratops. And in all three examples (Centrosaurus included), the juveniles have parietal fenestrae!
For Triceratops to transition into Torosaurus requires some pretty heavy special pleading. I'm not comfortable with that. I need more evidence. I need people to show their work. You've got a boatload of Triceratops specimens? Great. Publish some kind of photoessay, either in a print or online journal or, hell, Ye Olde Internet, showing me and everybody else the full goddamn range of Triceratops variability, which as you keep saying, is insane. Prove that there is not a single effing skull variable that cannot be explained away as either age-related, and therefore not phylogenetically informative, or individual variation, which must be staggeringly huge. Midline epioccipital? Nope. Number of epiossifications? Sorry. Horn size/angle? No dice. Basic things like timing of age-related characters? Not gonna happen.
Look, Pachyrhinosaurus lakustai displays some pretty widespread individual variation, too, but at least we know it's Pachyrhinosaurus lakustai! It's not like Einiosaurus has a mid-life crisis and transforms overnight (thus hiding all transitional evidence) into Pachyrhinosaurus. That's not really how this works. Pachyrhinosaurus is diagnosable across the spectrum of individual variation. And hey, Triceratops clearly is, too. The question is whether all that individual variation has anything to do with what Torosaurus looks like.
I mean, it's one thing to say that Triceratops occupies a wide range of individual morphological variation. I can buy that. But it's tough for me when you start saying that Triceratops exhibits an incredibly wide range of individual growth timing variation. I know, I know, you've got that warehouse full of Triceratops specimens. One might be a big individual with little skull suture fusion, and one might be a small individual with lots of skull fusion. So, in theory, ANSP 15192 could just be a Trike that hit its growth spurt way too early, and Tatankaceratops is the Trike equivalent of Benjamin Button. But here's where my problem is: given that Triceratops apparently ages as fast as it goddamn pleases and exhibits more variation than Varanus, how can we adequately test the "Toroceratops" hypothesis?
Is nothing sacred? What kind of rubrik can you use when there is no rubrik? Scannella continues to argue that bone histology and microstructure is the only real way to figure out who's who, but we've already seen that the growth dynamics of Triceratops are apparently not set in stone. All you can really tell is whether Triceratops (or Torosaurus) is still growing or not. Just because your Triceratops is still growing does NOT mean that Torosaurus is the obvious next step. Can we get some postcranial, long-bone histology done? If all the Torosaurus skeletons are older than Triceratops skeletons, then slap my mouth wide open--THAT is good evidence.
Or wait, maybe it's not. After all, Triceratops wasn't keeping a firm growth schedule. ANSP 15192 might just be a Triceratops that started its transition really early, while the Triceratops individuals who appear to be older than ANSP 15192 just decided they liked having short frills. It's hard for me to believe that Triceratops figured out how to avoid the age-related growth dynamics that shackle the rest of us.
You can't sit there and tell me that, out of all the ceratopsids known and studied, and in fact most animals in the world, Triceratops was unique in its growth timing and morphology. Tyrannosaurus rex has a wierd growth curve for a tyrannosaur (or, indeed, any big theropod) but guess what? It's consistent! You can age a tyrannosaur. You apparently can't age a Triceratops. There must be certain morphological characteristics that appear at certain age ranges. Hell, it's been demonstrated for Triceratops by Horner & Goodwin! Are we abandoning that research now? The full range of variability in Triceratops apparently wipes out the morphological characters that define each age class, so are we just fucked?
I need consistency. I cannot abide it when Farke or Longrich & Field come up with testable cranial characteristics and they are basically brushed aside with this "that variable is too variable" comment. Meanwhile, Torosaurus must be Triceratops. Because THAT variable is not up for debate. It's clear as mud.
And what about all the strange variations on Triceratops that have cropped up lately? Tatankaceratops, Ojoceratops, and Eotriceratops? Are they all just somewhere on the incredibly generous bell curve of individual variation on Triceratops? I mean, they probably are! Shit, you could probably find other chasmosaurine genera that fit in that range of variation. Let's get Arrhinoceratops in that line! Aside from the slightly squared-off frill, he doesn't look too horribly different. And there are probably plenty of Triceratops specimens with slightly squared-off frills.
My point is that there needs to be a testable rubrik for "Toroceratops" to work or even not work. You can't just say "Triceratops is really variable, therefore Torosaurus." There have to be established baseline growth trajectories. I will say this: I am NOT opposed to the "Toroceratops" hypothesis. If it's true, it's intruiging and, apparently, unique among ceratopsids. But there is SO much more than needs to be done, and I don't like how the conversation is going. I don't care how much data you have if you're not sharing it with the rest of the class.
That is all. Rant over. I have a PowerPoint to work on.