HTML Tags for spacing

I GIVE UP, e-Blogger! I BEND TO YOUR WHIM!

Does anybody out there know the HTML tag for making a paragraph break? You know, when you get to the end of a sentance and then press "Enter" twice?

Like this?

Whenever I get toward the end of a post, e-Blogger just decides that it doesn't want to do automatic paragraphs anymore, and things squeeze together, like they did in my last post after the Diceratops photo. But now that I can use italics and boldface and links but I can't figure out paragraphs. Help me, please!

Eotriceratops xerinsularis, Part Deux

Having now read Eotriceratops' paper (thanks again to my loyal readers!), I've got a few complaints about it. First and foremost, there is no skull reconstruction! This could be because the frill is so incomplete, but otherwise there's enough to draw something toward the end of the paper. But no, we just get drawings and photos of individual bones. All I've got to on are two photos of questionable quality from various news sources (the one above is from Discovery News, and it's the best picture I could find).

This is a topic I feel very strongly about. Since there are no living non-avian dinosaurs, it is imperative that paleontologists put some effort into reconstructing an animal when such a reconstruction is appropriate. We don't need an awesome painting by an esteemed paleo-artist accompanying every scientific paper, but a reconstruction of the known parts would help give me an image from which to base my own musings and reconstructions on. Now, there are some taxa which should not be reconstructed (yet). Masiakasaurus is one of them. It's tough to draw an entire animal when the only really informative parts you have are the legs and dentary. Noasaurs are tough enough due to their fragmentary nature, but when you throw a tooth curveball in there, I find it extremely questionable to reconstruct the rest of the bugger's head as pretty normal.

Think about that. What if Masiakasaurus has some sort of ridiculous crest on its head like Guanlong or its sister family, the Abelisauridae? Until more fossils are found, I think that a full reconstruction is premature. Every picture of Masiakasaurus I've seen, by the way, have been essentially based on the original headshot, which appeared on the cover of Nature the week it was described.

Anyway, at the other end of the spectrum, you've got taxa which are known from a lot of good material--certainly enough to warrant a picture of the head, but no reconstruction is given. Eotriceratops is one example, but there are others. The worst offender I've ever read was Mapusaurus, a giant South American theropod known from several individuals of various growth stages. Almost the entire skeleton is known. But it's description, by Coria & Currie (2006) fail to provide even drawings of the individual bones, much less a reconstruction of the skeleton.

For me, if I can't draw it, I don't know what it looks like.

Anyway, if you want to read a good summary of the Eotriceratops paper, Brian's got you covered. He does well to point out the unusual bite marks on the base of one of the supraorbital horns. The paper itself, however, mentions the bite marks in passing, without speculating on how they got there or what made them. This is another failing of the description. Another disappointment is that you read the paper, which doesn't really consider the overall structure of the frill (except for an overly-long discussion on the unique epoccipitals), and then you look at the photos here and below, and suddenly the frill is solid (and huge).

According to the paper itself, the frill is largely unknown, so I'd be interested to hear their justification for not putting some fenestrae in there. In their phylogenetic analysis, Eotriceratops falls into one of two positions (both of which are equally parsimonious): Either it's a sister taxon to Triceratops, or an outgroup to Triceratops and (Diceratops + Torosaurus). Either way, you would expect to see some fenestrae in there, especially in the latter hypothesis.

Keep in mind that Triceratops, as Brain notes, is unique among horned dinosaurs in lacking windows in its frill. Aside from providing an interesting question as to where the animal's jaw muscles attached, the strange frill has actually obscured Triceratops' true affinities, as its frill is more like that of a centrosaurine. Anyway, since the closed frill is obviously a derived feature, one would expect that an ancestral Triceratops would have at least small fenestrae. And if Eotriceratops is ancestral to the entire "Triceratops group," then I would almost require it to have holes in the frill. No justification for a lack of holes is given, and that really annoys me.

Finally, somebody really needs to redescribe Diceratops. The Eotriceratops paper treats it as not just a separate, distinct genus, but also as a sister taxon to Torosaurus rather than Triceratops! The picture directly above, by the way, is a reconstructed Diceratops skull. Although I'm not entirely surprised that it was found as a sister taxon to Torosaurus (looks a lot like it ahead of the frill), to see it suddenly move from "possible synonym of Triceratops" to "sister taxon of Torosaurus" is a little strange*.

So I wasn't terribly impressed with the Eotriceratops paper, for the reasons set forth above. And we need more information on Diceratops. One last thing! Does anybody out there in readerland have Albertaceratops' paper? I would love to do a reconstruction of that critter, but I need its description first!

*To be fair, Diceratops shares Torosaurus' vertically-oriented supraorbital horns and low nasal horn, but the frill just screams Triceratops.

Eotriceratops xerinsularis

It sort of makes me mad that this is the only picture of Eotriceratops making the rounds on the web right now. It's a horrible picture, and clearly a sculpture rather than the actual fossil. I want to see the bones, dammit! But look at the size of that monster! E. xerinsularis was just published last week in the Canadian Journal of Earth Sciences, and its authors suggest that it belongs in a group including Triceratops, Torosaurus, and Diceratops. Eotriceratops is known from deposits significantly older than those ceratopsids, though. Its head is apparently the size of a European SmartCar, and is quite a bit larger than typical Triceratops skulls. What shocks me about the skull is that, despite its ridiculous absolute size (which approaches the current record-holders, Pentaceratops and Torosaurus), the proportions of the skull are similar to those of Triceratops. It's as if Eotriceratops is a scaled-up Triceratops.

Like every other well-known ceratopsid, Eotriceratops' diagnostic characters are in its head, and its unique bones include the premaxilla, nasal horn core, squamosal, and epijugal. Seeing as there are obvious similarities between Eotriceratops and Triceratops, one wonder what the former can tell us about that most problematic of ceratopsine taxons, Diceratops. That misnamed genus was named by Lull in 1905 on the basis of a basically complete, but poorly preserved, single skull. While originally named Diceratops, the animal eventually fell under the Triceratops moniker, ironically, by Lull in 1933. What made Diceratops distinct at all? It has small holes in its frill--features that are present in all other ceratopsians, but not in Triceratops.

By the by, the lack of fenestrae in Triceratops' frill is generally considered an automorphy of that genus. Although the frill's small, rounded construction brings to mind the centrosaurines, the rest of Triceratops' skull is clearly of ceratopsine affinities. Given its close relatives--Torosaurus, Arrhinoceratops, and Pentaceratops, the small, rounded frill of Triceratops is a bit of a puzzle. Yet even juveniles are fenestrae-less, so the Triceratops' frill is a very distinct feature.

At any rate, Diceratops' frill has small holes behind the horn cores, and, oddly, one more just behind each postorbital fenestrae. Lull attributed these holes to either pathology or injury, suggesting that 'Diceratops' merely represented an old individual of Triceratops. Other more minor oddities of Diceratops include nearly vertically-oriented orbital horn cores, a rounded nasal horn core, and a proportionately shorter snout than most Triceratops specimens. Of course, Triceratops itself shows incredible individual diversity, as more than a dozen species were once recognized, all based on minor individual variations. That number has now been knocked down to just two species (and even these may be the result of sexual dimorphism): T. horridus and T. prorsus.

Since Lull's 1933 suggestion, Diceratops' true relationships have continued to provide debate. It has been called a sister species to Triceratops, an ancestral species (or genus) of Triceratops, or an old/injured Triceratops. In his extremely informative summary of the Ceratopsia, The Horned Dinosaurs, Peter Dodson declined to say for sure whether Diceratops was a distinct taxon or not, but since that 1996 tome, I have continued to see Diceratops treated as a unique genus in ceratopsian literature, and I wonder if Eotriceratops will illuminate its taxonomic position at all.

Many thanks to Jerry and Louis for sending me a copy of Eotriceratops' description. Now I'll be able to answser my own question (hopefully!). If any of you readers would like a copy, feel free to email me, and I can send it along.

When I Was a Child

I spent most of yesterday chilling, because it was my quarter-century birthday. That's right--I'm an old man. Of note, I got lots of birthday money from relatives, which I used to buy Super Mario Galaxy and Resident Evil: Umbrella Chronicles. Both are stupendously fun. My wife got me the new Stephen Colbert book and the first two seasons of South Park. My folks got me a big lizard-themed puzzle (I love puzzles), and my brother got me The Host. Sadly, I did not get any Dinostoreus skulls, which were at the top of my list (wherefore art thou, Ceratosaurus?).

I share my birthday weekend with my friend Marcus, who writes (every few months, it seems) at Of Warts and Other Matters. I don't think he has access to a computer right now, and his last post was in June, so...make of that what you will. At any rate, Marcus turned 22, and for his birthday I bestowed upon him a hand-colored, framed version of the comic you see above. He and I are big Pink Floyd fans, and any others familiar with that band's more famous lyrical odysseys may well recognize the text and, perhaps, the final wordless frame.

I know that Brian will appreciate the reference, anyway. One of these times I'll take the comic to Photoshop (or Corel) and paint it with pretty colors, but for now, enjoy the B&W version.

Stegosauropod?

My favorite animals are those that are not what they seem. Effigia, for example, is actually a crurotarsian which converged on dinosaurs. Henodus is the placodont answer to turtles, and Nigersaurus predated lawnmowers. And then you’ve got the contrary animals, of which Europasaurus is a member. A dwarf sauropod, can you believe it? While most sauropods were well over sixty feet long, and at least one may have hit the 150-foot mark, little Europasaurus was less than twenty feet long. But at least Europasaurus looks like a miniature sauropod. Aside from its dwarfism, it’s easily identified as a macronarian. Can’t say the same, though, for today’s freak sauropod. Brachytrachelopan mesai, a dicraeosaurid diplodocoid from Patagonia, is not only small overall, but also had an incredibly short neck.

Go figure. One of the defining characteristics of the Sauropodmorpha is a long neck, but Brachytrachelopan (rolls of the tongue, doesn’t it?) bucked that trend and decided to make its own bizarre fashion statement. Although the only well-preserved elements in the Brachytrachelopan type include articulated cervical and dorsal vertebrae (and an ilium) (and the distal end of the femur and proximal end of the tibia), and they are very strange indeed. Moving forward from the sacrum, the neural spines of the individual vertebrae begin to crane forward. The further toward the head you get, the more severe the forward bend. The dorsal/cervical transition is abrupt, and the cervical vertebrae are markedly smaller than the dorsals. Only eight cervicals are preserved, although the authors assume that Brachytrachelopan had the usual dicraeosaur complement of 12. I question this assumption, because the fifth cervical (the last preserved one) is so small that I wonder how far the head was from it.

The ribs also sweep back toward the pelvis, rather than straight down. The ilium itself is flared to allow at least two ribs to pass behind it. Only two and a half sacral vertebrae are preserved, although there may have been more. The neural spines are fused together, forming a solid block of bone above the pelvis. Sadly, the limb elements are not preserved in any informational capacity. The distal femur and proximal tibia pieces are similar to Dicraeosaurus. With those strange ribs, I wonder how the pectoral girdle attached.

Anyway, the cranially-curved neural spines of Brachytrachelopan, in addition to its meager neck, means that it was virtually unable to raise its head beyond a horizontal line, and even that could be stretching it. With its head perpectually facing the ground, perhaps facing it, one surmises that its food must have been gathered in a manner similar to that of Nigersaurus. Unfortunately, no skull material is known from Brachytrachelopan, and closely related Dicraeosaurus from Africa has a skull that's roughly similar to Diplodocus and Apatosaurus. Whether Brachytrachelopan varied wildly from this norm, as Nigersaurus did, remains to be seen.

Brachytrachelopan belongs to a third family of diplodocoids (aside from Diplodocidae and Rebbechisauridae): Dicraeosauridae. Only three genera are recognized. Dicraeosaurus seems to be the largest known member, at 40 feet long. Amargasaurus, the "spike-necked" sauropod from Argentina, was a mere 33 feet long. Brachytrachelopan is thought to have been less than 30 feet long. Dicraeosaurs are characterized by short necks, relatively small bodies (for sauropods), and unusually tall neural spines. Exactly what these sauropods were eating is a bit of a mystery, but in Brachytrachelopan's case, probably vegetation that was between 1 and 2 meters off the ground.

I think Brachytrachelopan looks an awful lot like a stegosaur, what with its robust limbs, tall neural spines, and short neck. Perhaps it was a Patagonian stegosaur mimic!

Rauhut, O. W. M., Remes, K., Fechner, R., Cladera, G. & Puerta, P. (2006). Discovery of a short-necked sauropod dinosaur from the Late Jurassic of Patagonia. Nature 435: 670-672.

The Littlest Sauropod

Continuing the trend set by Nigersaurus this last week, I've decided to draw another unusually small sauropod (and I'll do yet another one in a few days!). This here is the ridiculously small Europasaurus holgeri, from the Late Jurassic of Germany. A group of individual animals, spanning an impressive range of sizes, was described in 2006. The smallest animal was 1.75 meters long, while the largest was 6.2 meters. Clearly, a growth series is represented here.

The animal's small size is attributed to insular dwarfism. Remember those mammoths that survived on Russian islands until a few thousand years ago? That's also insular dwarfism. Large animals tend to become dwarves when they're stranded on islands, and the food supply is limited. We know that Europasaurus is a dwarf (and not just a juvenile) thanks to its growth rings. When animals are growing quickly, they lay down rings with long intervals between them. As the animal grows more slowly, or not at all, the rings are deposited very close together. In the largest Europasaurus individual, there were a few far-apart growth lines, and then, near the outer edges of the bone, the growth lines are tightly packed. So not only was the largest individual quite small, it was also fully grown.

The authors argue that Europasaurus drawfed itself by slowing its growth rate by comparison to larger neosauropods like Camarasaurus and Brachiosaurus. Speaking of those macronarians, a cladistic analysis posits Europasaurus fallings between Camarasaurus and Brachiosaurus among macronarians. One wonders what kind of dwarf theropod hunted this little sauropod (if any). Next up: Brachytrachelopan!

Reference:

Sander, P. M., Mateus, O., Laven, T. & Knotschke, N. (2006). Bone histology indicates insular dwarfism in a new Late Jurassic sauropod dinosaur. Nature 414: 739-741.

Updated Blogroll

I finally got around to adding two more blogs to my blogroll. Darren Naish & Co. have already infected the paleo blogosphere with their extremely well-written, funny, and educational Sauropod Vertebrae Picture of the Week (SV-POW!). If you didn't know about the anatomy of a vertebrae before, you will soon. I never understood how diagnostic individual pieces of one's spine could be until now!

Also, Catalogue of Organisms is up. I'm starting to read it, and it's so very good! I must apologize profusely to Chris Taylor for not adding him sooner, or even realizing that his blog existed! I didn't know where Boneyard IX would be, and actually forgot all about it, only to find that he was hosting it (after the fact). Chris was good enough to not only link to one of my posts (which I hadn't even prepared for the Boneyard) but also to add my humble blog to his blogroll!

Lawnmowers of the Early Cretaceous

Nigersaurus taqueti is not new. In fact, this most bizarre of rebbachisaurs has been known since at least 1999, when Paul Sereno named it. Nigersaurus was mentioned ever so briefly in a 1999 Science article called "Cretaceous sauropods from the Sahara and the uneven rate of skeletal evolution among dinosaurs." It didn't get a formal description until 2005, though, when Sereno & Wilson published "Structure & Evolution of a Sauropod Tooth Battery" in the excellent The Sauropods: Evolution and Paleobiology. And even that paper was not a full description--Sereno & Wilson basically muse over its bizarre skull and dentition for 19 pages.

A full description of the animal was just published, however, in the free online journal PLoS. This is a signficant step for Sereno, who usually publishes in big name journals like Science and Nature, which are NOT free online. PLoS is, and you should all immediately check out the description. The link is above.
What makes Nigersaurus so special is its extremely strange dentition. The muzzle is wide and squared off, and chisel-like teeth are present only at the front of the mouth. The animal has lost its supratemporal fenestrae entirely, seemingly to make room for the orbits, which are enormous and have recessed to the back of the head. The external nares are recessed, but not as much as in its diplodocid cousins. Looking at the skull from the top, it becomes obvious that the tooth-bearing front of the skull is actually wider than the back of the skull. The mandible is roughly U-shaped and, again, the dentaries are ridiculously wide and squared-off.

In essence, what Nigersaurus has developed is a perfect tool for grazing. But unlike ceratopsians and hadrosaurs, who cropped their food with a beak and then chewed up the tough plant matter with molar analogues, Nigersaurus was capable only of the cropping. There are no other teeth in its mouth, so cropped plant material would have been swallowed whole. Even if it had the equipment, however, it's not clear whether Nigersaurus would have even been capable of chewing. It's skull is amazingly lightweight, full of holes, and the bones are extremely thin. In the skull and manidble, five accessory fenestrae have opened up. Two of them are in the jugal bone, which itself is already thin and strut-like.

The animal's quadratojugal has also lengthed considerably compared to its forebearers, effectively dropping the mandible's articulation. Nigersaurus could open its jaw quite wide. When seen from the side, the skull (with a closed mouth) looks amazingly "open," what with all the large fenestrae and huge gap between the bottom of the skull and the top of the mandible. It looks like a rodent--a rodent without molars. The thickest parts of the skull are the tooth-bearing pieces: the premaxilla, maxilla, and dentary. These bones are full of vascular channels, implying a beak-like structure, which would have further strengthened the cropping structure.

Nigersaurus also gives the first reasonably complete endocast of a sauropod. Although I would strongly hesitate to generalize Nigersaurus' brain across the sauropod spectrum (given it's strange skull and habits), it does show that smell may not have been very important to Nigersaurus (its olfactory bulbs are quite small), and that Nigersaurus has an incredibly small brain compared to like-sized ornithischian and non-coelurosaurian theropods.

Another area of interest is that Nigersaurus' inner ear suggests that its head was held, so that its muzzle pointed directly downward. This posture may shed light on why its orbits are so large--perhaps it needed good vision to see predators coming from both sides while it's head was among the horsetails. This is not to say that Nigersaurus was unable to lift its neck, but only that it's head came off the spine in such a way that it would have had to bend at the neck in order to "straighten" the head, as my introductory restoration shows. Sereno, et al. suggest that, based on both this new animal and past research by Stevens & Parrish, that diplodocids in general were ground-based feeders. This idea is not entirely unexpected, and the feeding strategies of Diplodocus and Nigersaurus may indeed have been similar. The chisel-shaped dentition of Diplododcus is basically the same (though larger) as Nigersaurus, but Diplodocus had a more rounded muzzle. Nigersaurus and its family, the Rebbechisauridae, may simply constitute an extreme ground-grazer.

And now we must ask what Nigersaurus ate. Grass has turned up in Late Cretaceous India thanks to some titanosaur droppings, but Nigersaurus lived in the Early Cretaceous of Egypt, so we cannot assume that it was munching on grasses. It would have made an excellent grass-eater, though. Sereno, et al. suggest that, given the animal's weak skull construction and reduced bite force, Nigersaurus consumed horsetails and immature ferns. Since it lived in an area dominated by floodplains and river systems, it's possible that Nigersaurus feasted on shallow-water vegetation as well.

I should also mention that its teeth had a replacement rate of perhaps one per month, meaning that this critter was growing new teeth at a near-constant rate, even faster than ornithischians! Wear patterns on the chisel-shaped teeth indicate strong tooth-to-tooth contact, and I can easily see the upper and lower teeth chipping themselves down to nubbins in no time. Is it possible that, like rodents, Nigersaurus' teeth grew at a constant rate so that it always had teeth to grind? I'm not entirely sure how reptilian tooth replacement works. When a theropod loses a tooth, for example, does the old root just fall out and the new tooth erupts within a day or two? And how would it work for a sauropod like Nigersaurus?

Aside from its skull, Nigersaurus' skeleton is fairly typical of a diplodocid. It has a short neck, though not as short as Brachytrachelopan! It retains a long tail with rod-like elements towards its end, like other diplodocids. At thirty feet long, though, it's a fairly small sauropod, and I wonder who was hunting it? Nigersaurus is certainly one of the strangest sauropods I've ever seen, and that's exciting. It demonstrates that these big beasties weren't nearly as conservative as we generally think, and it adds to the incredible diversity that the Dinosauria has managed to show off in the last few decades.

Citations:

Sereno, P. C., Wilson, J. A., Witmer, L. M., Whitlock, J. A., Maga, A., Ide, O. & Rowe, T. A. (2007). Structural extremes in a Cretaceous dinosaur. PLoS One (11): published online.

Sereno, P. C. & Wilson, J. A. (2005). Structure and evolution of a sauropod tooth battery. In: Curry Rodgers, K. A. & Wilson, J. A. (eds). The Sauropods: Evolution and Paleobiology. University of California Press, Berkeley. Pp. 157-177.

Sereno, P.C., Beck. A. L., Dutheil, D. B., Larsson, H. C. E., Lyon, G. H., Moussa, B., Sadlier, R. W., Sidor, C. A., Varricchio, D. J., Wilson, G. P. & Wilson, J. A. (1999). Cretaceous sauropods from the Sahara and the uneven rate of skeletal evolution among dinosaurs. Science 284: 798-800.

Stevens, K. A. & Parrish, M. J. (2005). Digital reconstructions of sauropod dinosaurs and implications for feeding. In: Curry Rodgers, K. A. & Wilson, J. A. (eds). The Sauropods: Evolution and Paleobiology. University of California Press, Berkeley. Pp. 178-200.

Stevens, K. A. & Parrish, M. J. (2005). Neck posture, dentition, and feeding strategies in Jurassic sauropod dinosaurs. In: Tidwell, V. & Carpenter, K. (eds). Thunder-Lizards: The Sauropodmorph Dinosaurs. Indiana University Press, Bloomington & Indianapolis. Pp. 212-232.

Illustrations by Zachary Miller, 2007.

This story makes me laugh!

National Geographic News has a story up that is actually also at The Dragons Tales and Pondering Pikaia, but I had to post it here, too. Every time I see the picture accompanying the article, I laugh. Those poor critters could not have died at a more convenient time. This is better than that Fish-within-a-fish fossil at the Hayes Museum of Natural History in Kansas, which is actually pretty impressive by itself.

Note: People in Kansas are nuts about this fossil. Xiphactinus audax, an enormous ray-fin, had swallowed a smaller Gillicus arcuatus, and they apparently died. The Gillicus is fully articulated, having been swallowed whole by the giant predator. Whenever I go down to Kansas (basically every year), the extended family asks if I've seen the "fish-within-a-fish" yet. And you know, the Hayes museum has a bunch of more impressive fossils, like mosasaurs. But no, everybody wants to see the enormous salmon. It's a fish!

Note Part 2: I know it's not aactually a salmon.

Yes, I know, non-avian maniraptors had uncinates, too.

There's a new paper out at the Royal Society, finally detailing one of the more ignored aspects of maniraptoran anatomy: the uncinate processes. Codd, et al. for perhaps the first time as far as I can remember, actually discusses the role and phylogenetic importance of these structures, which must have been quite widespread among the Maniraptora. The role of these rib protrusions has never been entirely clear, but Codd, et al. suspect that they have something to do with respiration. I had always learned that the uncinates strengthened the boxy structure of a bird's torso. While this is almost certainly one part of the equasion, it would seem that uncinates serve several purposes. Of minor importance is that, at least in Sphenodon punctatus (tuatara), the uncinates connect to the gastralia via external oblique muscles. Non-avian maniraptoran dinosaurs (and even some avian ones) seem to have had well-developed gastralia, so that function may have been retained.

But more importantly, in modern birds, the uncinates act as levers that, together with muscle action and sternal ribs, actually raise and lower the sternum during respiration. The "pump" action of the sternum has long been known as a major factor in avian breathing, but it's surprising to see the uncinates actually facilitating this movement. But that's not even the focus of the paper. Rather, Codd et al. merely strive to understand the phylogenetic consequences of uncinates in the Theropoda, and what that might mean for theropod activity levels.

The paper is actually disappointingly short, especially when you realize that it could've actually been shorter. It turns out that uncinate processes have a fuzzy preservation record. This should not surprise us, because they are attached to the ribs with cartilage, and the processes themselves were thin, strut-like bones. At any rate, they are only known with certainty in Oviraptor, Citipati, Khaan, Velociraptor, Deinonychus, and Microraptor. Thanks to phylogenetic bracketing, we can pretty safely conclude that the common ancestor, at least, of Oviraptor and Deinonychus also had uncinates. So that means we can expect to find more complete remains of, say, Nothronychus with uncinates, and troodontids, too.

In modern birds, the sternum's keel provides a key muscle attachement site for respiration, but Codd et al. suggest that, because non-avian maniraptors did not have keels, they may have retained their gastralia for essentially the same purpose. Short paper, but these are things that needed to be said!

Terrestrial Mesozoic Birds?

So the whole point of being a bird is to get up into the air, right? You're safe from predators up there, after all. You can raise your chicks, find food, and basically live it up without worrying about hungry terrestrial predators. The air and treetops represents a safe haven! So why wouldn't birds take advantage of it right away? As it turns out, they might not have. A new study in Current Biology by Christopher Glen & Michael Bennett suggests that, paradoxically, Mesozoic birds may have been primarily ground-lovers. The two authors came to this surprising conclusion by measuring the curvature of the claw of digit III in several Holocene and Mesozoic birds. They found that, in modern birds, claw curvature increases with degree of arboreality. Many birds, it turns out, forage on the ground. But many, many birds spend their days on the ground and in the trees. Among living species, a large spectrum is represented. Glen & Bennett created six categories to fit their birds into: "ground-based birds," "dedicated ground foragers," "predominantly ground foragers," "predominantly arboreal foragers," "dedicated arboreal foragers," and "vertical surface foragers."

For some idea of this spectrum, I'll list examples of birds which match the categories listed above: ostrich, chicken, pigeon, cuckoo, (no example given), woodpecker. Claw morphologies across modern groups seems to be indicative of degree of arboreal foraging--the more curved the claw, the more arboreal the bird.

Glen & Bennett measured the claws of several Mesozoic taxa, incuding Archaeopteryx, Microraptor, and Confuciusornis. Of all the Mesozoic birds sampled, only Sapeornis fell within the "predominant arboreal forager" category. All of the other ancient avians fell below that grouping, and were generally found to be either "dedicated ground foragers" or "predominant ground foragers." Not surprisingly, Caudipteryx fell within the "ground-based bird" category, while Pedopenna, Microraptor, Archaeopteryx, and Jeholornis were strong terrestrial in their habits.


The paper raises a number of questions. First, the very idea that birds "escaped" to the trees must be abandoned, if they did most of their business on the ground. One might be tempted to believe that, in China anyway, large predators did not exist to yet to threaten these largely terrestrial birds, but the recent discovery of dromaeosaur tracks in China indicates that a Deinonychus-sized predator existed alongside those smaller avian critters. Also, the motivation for the evolution of the reversed hallux must be questioned. While generally thought of as a means to perch, I think the idea that Archaeopteryx and its kin were spending a lot of time soilside downplays the importance of the hallux. Why did the reversed hallux evolve if trees were not the enormous draw we once thought they were?

These are important questions, and I'm happy to see that Glen & Bennett have brought them up. The trip from the ground to the trees may have been a lot more complicated than we awknowledge, but that's fine by me. It just means there's so much more to discover!

Hat-tips to Will and Brian, of course, for letting me know this story existed.

Glen, C. L. & Bennett, M. B. (2007). Foraging modes of Mesozoic birds and non-avian theropods. Current Biology 17(21): published online.

Li, R., Lockley, M. G., Makovicky, P. J., Matsukawa, M., Norell, M. A., Harris, J. D. & Liu, M. (2007). Behavioral and faunal implications of Early Cretaceous deinonychosaur trackways from China. Naturwissenschaften: published online.

Blogobituary: Eldridge the Chameleon, July-November, 2007

Mr. Eldridge the Chameleon, a mere six months old, died Friday night of a baterial gut infection. He is survived by his three leopard gecko friends, Liquid, Solid, and Mr. Fat. At the beginning of October, Eldridge stopped eating, ignoring and at times moving away from available food sources. Despite constant prodding by his owners, Eldridge began to deteriorate. I took him into the vet a few weeks ago, and the herp specialist believed that he had a bacterial infection, probably since before we bought him. He suggested I feed Eldridge baby food and get a stool sample. Although he ate a lot of baby food in the next two weeks, Eldridge did not seem to produce any fecal matter, and if he did, I was not home when he did his business (only a fresh sample would do).


Thusly, Eldridge died from a combination of starvation and gut infection. I would later learn thatn chameleons in general are very difficult to care for, and are prone to many kinds of infection, especially early in their lives. I had an adult Jackson chameleon for several years (this was a long time ago), and I got him when he was three, and he died when he was six. The average lifespan of male Jacksons is five. Although I was reluctant to buy another lizard from the pet store (might it also have an infection?), I purchase a frog-eyed gecko today from a different, newer pet store (Petzoo). He looks very healthy (and weird) and fits comfortably in Eldridge's old tank, albeit with changes to the environment.


I wanted to salvage Eldridge's skull, but he was so tiny that his bones would have boiled away with the meat. He ended up being put in the garage trash can. :-(


While this is not a picture of the new gecko itself (which I named Big Boss), it is a picture of a frog-eyed gecko.

Frog-eyes are burrowing geckos, and look like a transitional form between wall-crawling geckos and leopard geckos. Like the latter, frog-eyes have no laminae on their toes but instead posess sharp claws. They are burrowing lizards (moreso than leopards) and tend to have the spotted pattern which is so unique to leopard geckos. Their scales overlap, leading to concerns that a sandy substrate could get stuck between their scales. I've read conflicting reports, so bought a small bag of quartz sand for a base layer, and wood chips for an upper layer. He seems to like the quartz sand. Unlike leopard geckos, but like wall-crawlers, frog-eyes lack eyelids and have un-segmented tails. Frog-eyes are comical thanks to their oversized, cone-shaped heads.

Apparently, frog-eyes should not be handled very often, as their scales easily pop off and they become prone to infection (again with the infections!). Leopards have interconnecting scales and are basically smooth-skinned. In all my years with my leopards, I have never seen them cut or injured. Frog-eyes also have a reputation (on the interweb anyway) for being aggressive and difficult to tame. We'll see about that!