Toro! Toro! Toro!

Above: Ceratopsian skull specimen AMNH 5116. Triceratops, Torosaurus... or both? Read on...

By now, all dino fans have probably heard the buzz on the indicator: Jack Horner and team are working on a paper which attempts to prove that Torosaurus and Triceratops are the same thing, and that in general, growth series in dinosaurs are often misinterpreted as numerous similar species (something that has long been acknowledged in pterosaurs and recently in early birds like Archaeopteryx and, probably, Confuciusornis).

Here's the quick and dirty background: Triceratops was named by O.C. Marsh in 1889 based on a pair of horns and skull roof collected in 1887 from Colorado. Numerous complete specimens followed, making Triceratops the archetypal horned dinosaur with its two long forward-pointing brow horns and single short, forward-pointing nose horn, in front of a relatively short (by ceratopsian standards), solid frill. The frill is notable: most ceratopsians, including close relatives of Triceratops, have long frills with large openings, or fenestrae, in the bone.

Torosaurus was described a few years later in 1891, also by Marsh, based on two skulls. Unlike Triceratops, the Torosaurus skulls had long frills with the standard fenestrae. Its frill was also smooth around the edges: many Triceratops specimens show that they had small, bony scutes adorning the frill's edge, called epoccipitals.

According to Horner's talks at SVP, which he also summarized in an interview on the podcast The Skeptic's Guide to the Universe (available here), those differences are not due to species variation, or even sexual dimorphism as previously hinted. Rather, Torosaurus is nothing more than the most mature growth stage of Triceratops. The paper isn't out yet so all the data isn't available, but presumably Horner will demonstrate based on microscopic bone growth studies that all the specimens currently assigned to Triceratops are not fully mature, and that like modern birds, some secondary sexual characteristics (such as the expanded, chasm-filled frill) pop up quite suddenly at the 'last minute' in the animal's growth, after it has already reached nearly adult size.

Above: Diagram of a 'classic' Torosaurus skull. By William Diller Matthew, 1915. Public domain.

We can already see heaps of major changes taking place as Triceratops grows. Juveniles have backward curving horns, which completely change to point forward during growth. Remember those epoccipital fringes, the lack of which is so diagnostic of Torosaurus? We already see them becoming reduced from tall, pointed osteoderms in younger forms to smooth and rounded, and finally merging with the frill itself and smoothing out so as to be almost invisible. Indeed, in these oldest individuals, the bone in the center of the frill can also be seen to thin like a man's receding hairline. Given that we already know all of this about Trike's growth, it's not a very huge leap to recognize a long, smooth, holy frill as the next logical step, and those just happen to have been named Torosaurus for 110 years.

The goss has been flying over this online, and a few interesting tidbits have come up. Having grown up in the Northeast US, the most interesting to me concerns the mistaken identity of some specimens of Triceratops. For me, the quintessential Triceratops is the one in the American Museum of Natural History (specimen AMNH 5116). However, as many have pointed out on DinoForum and elsewhere, it's also among the most... well, un-Triceratops like.

Above: Triceratops skull 'classic' vs. specimen AMNH 5116. By Ed T. and Michael Gray (right), licensed.

Compare the images above. On the right is my beloved AMNH Trike. On the left is a 'classic' Triceratops skull. The frill on the AMNH specimen is longer, and lacks epoccipitals. The frill is also tall and back-swept, not flared out to the sides, as in most Triceratops skulls. Not only that, but as you can see in the image at the top of this post (which is a more contrasty view of the same AMNH skull), almost all of the frill has been restored in plaster to conform with what a Trike should look like. There are significant gaps in the middle of the frill entirely filled with plaster... exactly where the fenestrae of Torosaurus go. If Torosaurus and Triceratops are indeed separate species, the AMNH Trike is no Trike at all... it's a Torosaurus in disguise!

Thankfully, it's more than likely that there is no such thing as Torosaurus, any more than there was a Brontosaurus. It's all Triceratops baby, and we can conclude that this famous last of the ceratopsians was indeed last, the only one of its kind in the Lance and Hell Creek Formations that date to the very end of the Mesozoic era.

But... wait... isn't there another named ceratopsian from the same time and place? Named BEFORE Triceratops?? If there was only one Lance/Hell Creek ceratopsian, then Torosaurus get sunk into Triceratops as a synonyms. Does Triceratops then have to be abandoned in favor of... Agathaumas!?

Above: Painting of Agathaumas by Charles R. Knight, 1897. Public domain.

Dun dun duuuuuun!

Meet the Megaraptors

Above: Illustration of the megaraptoran Australovenator by T. Tischler, licensed.

Well, that all came together...

The history of Megaraptor is long and sordid. It was first described as a gigantic dromaeosaurid (hence the name), on the basis of a large sickle-claw found in Argentina. In fact, I remember a time when rumors circulated that the newly described Unenlagia might turn out to be a juvenile form Ironically, an ACTUAL gigantic unenlagiine dromaeosaurid from almost the same time and place was later found, in the form of Austroraptor. Not to be confused with Austrovenator, which, see below...

Then, a complete Megaraptor forelimb was found that crushed the dreams of every 12 year old Jurassic Park fanboy who had already adopted Megaraptor as their personal mascot: The giant claw came from the hand, not the foot, and it was no raptor at all: but what was it? The first thing that comes to mind is the similar story of Baryonyx ("heavy claw"), named for a similar giant claw that was similarly thought to come from the foot of a dromaeosaur, and similarly later found to come from the hand (have we learned nothing?). Baryonyx was actually a spinosaur, and the large hand claw seemed to be a unique feature of that group. So, was Megaraptor a spinosaur? Opinion was divided for years, with Megaraptor being placed either among the spinosaurs, the carcharodontosaurids*, or in some weird, new family of tetanuran theropods.

Above: Replica of a Megaraptor claw. Photo by Haplochromis, licensed.

The picture got clearer with a few discoveries in just the past year from 'Stralia. First, a large claw that looked suspiciously like the hand claw of Megaraptor, followed by a more complete specimen of a similar animal, named Australovenator. Australovenator looked like a good cantidate for a Megaraptor relative, and studies showed it was in fact an allosaur, somewhere between Allosaurus and carcharodontosaurids.

Well, a new study online today helps clarify the situation a whole lot. Benson, Carrano and Brusatte ran a massive phylogenetic analysis of allosauroids, and recovered a monophyletic clade that happens to include almost every oddball misfit theropod in the book. Called Neovenatoridae, this new clade includes the titular Neovenator (at times thought to be an advanced allosaurid or primitive carcharodontosaurid) and the enigmatic Chilantaisaurus, also previously thought to be a spinosaur. Neovenatorids more advanced than those two are placed in the advanced unranked clade Megaraptora (a nice compliment to the dromaeosaurid clade Microraptoria), which includes Megaraptor and Australovenator as well as perennial phylogenetic stragglers Aeroseon, Fukuiraptor and Orkoraptor. This true identity for Orkoraptor (previously thought to be a coelurosaur) is particularly interesting, since it lived so recently--only 70 million years ago, close to the end of the Mesozoic, showing that derived allosaurs lived right to the end, rather than dieing out in the mid-Cretaceous as previously thought.

All in all, this new paper is pretty major. It reveals a new clade of theropods of a type not really known before, even though none of the constituent species is actually new. What all the megaraptors have in common is a light, gracile build with often hollow bones (seen in the extreme case of Aerosteon), relatively long front and hind limbs (indicating a fast-running lifestyle) and large, hooked claws on the hands for grappling prey. Basically, this advanced line of "coelurosaur mimicking" allosaurs survived in the southern hemisphere while coelurosaurian carnivores were dominating the northern continents, during and after the time of their traditionally carnosaurian relatives carcharodontosaurids.

* I had to stop myself from writing "carcharodontosaurian" instead of "-id" a few times. See, neovenatorids and carcharodontosaurids are sister groups, and the clade containing both has been named Carcharodontosauria. So, technically, Megaraptor is a carcharodontosaur after all, just not a carcharodontosaurid proper.

The Near-Bird Cometh

Above: New specimen of Anchiornis and skeletal showing feather proportions, from Hu et al. 2009. Click to embiggen.

If you've been carefully combing Dave Hone's blog for the last nine months or so (and who hasn't been?), you'll know that the initial reports on headless fossil of an interestingly bird-like supposed avialan named Anchiornis were just a warning shot. Dave reported in December of last year that protobird fans could look forward to several more complete specimens that had been recovered and not yet described. Well, it looks like the first of these is pending: J. Brougham over at Wikipedia has published a few details and a full cite from the upcoming October 1 issue of Nature, which contains the description of a nearly complete specimen preserving such cool details as a complete skull, Microraptor-style hind wings and head crest, and a phylogenetic anlysis that finds Anchiornis is in fact a basal, mid-late Jurassic troodontid (!), totally stealing Scott Hartman's thunder. If this is the case, that is, if Anchiornis can actually be demonstrated as a troodont (or even just non-dromaeosaurid) with large airfoils on the hind legs, the argument that all deinonychosaurs or even all birds went through a gliding tetrapteryx stage and are secondarily flightless to some degree just got pretty darn rock solid. Greg Paul, throw yourself a party, and set a place for William Beebe.

Being a protobird fan myself, this prompted me to immediately go to the nature.com online preprint section and start clicking refresh faster than you can whip a ram at Brewfest. Needless to say I was dissapointed and will have to start hounding J. about the paper until something pops up on the DML to whet my appetite for photos so I can get started drawing this thing. More to come one I have a chance to read the paper and collect some goss!

UPDATE:
Just been informed that not only is this on Nature's front page, but the pdf appears to be free? Or is it because I'm logged in?

Raptorex update

Above: Recon of Raptorex by Todd Marshall, from CBC News.

Quick taxonomic update: Having just gotten the paper, I can comment that Bill Parker's concerns over the name Raptorex kriegsteini (see previous post), echoed on the DML, are based on misrepresentation of the issue by the newspaper reports. At least one news story said that Kriegstein named the species after his parents, so by ICZN rules the species name needs to be R. kriegsteinorum (-orum being the correct suffix for a name honoring multiple people). However, the paper explicitly states that the species is named only for Roman Kriegstein, so the current name is correct. For the record, here's the entire etymology section from Sereno et al. 2009:

Etymology: raptor, plunderer (Greek); rex, king (Greek); kriegsteini, after Roman Kriegstein, in whose honor the specimen was secured for scientific study.

Also, the paper makes clear that, unlike I speculated before, Guanlong, Dilong and friends are still recovered as tyrannosauroids in the paper's cladogram, though more basal than Raptorex.

Raptorex. For serious, that's a real dinosaur now.

Above: Paul Sereno with a model and skull cast of Raptorex, possibly the most ridiculously named dinosaur of all time. Photo from Chicago Tribune by Nancy Stone.

Headline: DeviantArtist Honoured with Dinosaur Name

Well not really, but surely raptorex must be stoked that his (let's face it), fun but pretty ridiculous username is now the name of a real life dinosaur, Raptorex kriegsteini.

The mini-tyrannosaur is from the Yixian ash beds (not the more famous lake sediments that preserve feathers), and is a bit improbable in other ways than its name. It looks like a mini-Tarbosaurus, with short, two-fingered hands and long, running legs, all things expected from a juvenile tyrannosaurid, rather than a (supposed) primitive tyrannosauroid like Dilong or Guanlong. I wonder if this has implications for their position as basal tyrannosaurs--the paper, supposedly released in the online edition of Science today, is nowhere to be found, for my part.

Raptorex also has a sordid past. Apparently, the fossil was smuggled out of China and sold at (where else) the Tuscon fossil show to a private collector for tens of thousands of dollars. The collector, ophthalmologist Henry Kriegstein (whose family name is honored in the specific name of the new dino), had specialists in Utah prep it out of its matrix so he could mount it in his Massachusetts living room. Upon discovering the specimen was not a juvi tarb as advertised, but rather a full-grown individual, Paul Sereno (so that explains the name!) was called in for further advice, and recognized it as an important discovery. Kriegstein soon agreed to relinquish his purchase to science (with a bonus in the form of naming rights, of course. At least he wasn't a big Bambi fan).

In a bit of taxonomic goss, Bill Parker over at Chinleana notes that, as Kriegstein technically named the genus for his parents, not himself (which is frowned upon), the ICZN mandates that the species name needs to be emended to kriegsteinorum, so watch for that change in the future, likely published by George Olshevsky or a similar stickler for proper Latin.

And, of course, Jack Horner has weighed in. In an email to Wired.com, Horner explained that he thinks the small, fleet-footed Raptorex, because it has the same body plan as larger tyrannosaurs, somehow proves that tyrannosaurs evolved into pure scavengers early on, and that the authors are jumping to conclusions in thinking that long, speed-designed legs somehow imply "predator." Keep on keepin' on, Horner.

Oh Giraffatitan, where art thou?

Above: Skull of Brachiosaurus altithorax (right, from Carpenter & Tidwell, 1998) and "B." brancai (left, by Gunner Rias, licensed).

A curious bit of goss, and potential drama?, teased out Mike Taylor and crew at SV-POW.

In recent posts about a new brachiosaurid announced last week, Qiaowanlong (or is it a brachiosaurid? See SV-POW for in-depth coverage), Mike Taylor consistently reffers to the genus "Brachiosaurus" brancai.

The goss stems form use of the quotes. As we all know, when discussing scientific names, the genus and species are always put in italics. The exception to this are nomina nuda, which are names not properly described or coined. Another exception is when a genus and species combo is found to be invalid for whatever reason. For example, the name Ingenia, for an oviraptorid, is preoccupied and has not yet been renamed. But the species name yanshini is still valid. So, when we talk about this species, we might write it as "Ingenia" yanshini to indicate that the genus name is going to change.

Similarly, this same notation is used for species previously assigned to one genus but are no longer considered related to that genus' type, and are pending reclassification under a new genus name. For example, the species "Dilophosaurus" sinensis is probably not closely related to Dilophosaurus wetherilli, so it gets quotes until a replacement name is chosen. This is also the current situation with "Brachiosaurus" brancai. Many people have suspected that this African sauropod is not the closest relative of the North american type species, Brachiosaurus altithorax, given that a B. altithorax skull has been identified that differs from the African species (see photos above), among other differences in skeletal shape and proportion.

So what's wrong with using quotes when talking about "B." brancai? The African version has already been given a new name! In a 1988 paper, Greg Paul coined the name Giraffatitan for a distinct "subgenus" containing the African species. This was later formalized as a genus name, I believe by Olshevsky in his Mesozoic Meanderings, but correct me if I'm wrong.

So wy write "Brachiosaurus" brancai when, if considering this a separate genus, it should rightly be Giraffatitan brancai? I asked Mike about it, and apparently a paper explaining will be coming out in a week or so. The goss at SV-POW for quite some time has been that the SV-POWsketeers favor a separate genus for "B." brancai, but the assumption was always that this would be Giraffatitan. Mike is playing coy for now--is it simply that the authors don't like the name Giraffatitan? Mike says this is the only paper he's seen in which the acknowledgments contain an apology, so it sure sounds like that is close to the truth...

But a valid name can't be rejected simply because an author doesn't like the sound of it. It would have to be argued away on technical grounds. Is the fact that Giraffatitan was originally a subgenus, not a proper genus, coming into play and allowing Giraffatitan to be re-named? Is the apology directed towards George Olshevsky (maybe the authors don't consider his self-publications valid?). I don't know the ins and outs of priority when it comes to subgenera and subspecies. But we'll know shortly...

The Colour and the Shape

Above: Iridescent Peacock feather, from Flickr. A new study shows that patterns, iridescence and even color can be preserved in fossil feathers.

Every dinosaur picture book aimed at kids comes with a disclaimer /slash/ incentive: "We don't really know what colors dinosaurs were." They were often depicted as green and drab, camouflage suited to their 1930s-era stint as lethargic reptilian swamp dwellers. But, the kid's books tantalizingly continue, "they could have been any color, with any pattern, even bright fuscha with purple polka dots!" (I'm guessing these books are to blame for Barney...).

Well, that's mostly true. We now know dinosaurs are more closely related to birds than modern reptiles (and lets not sell those short, many are very brightly colored). Birds have excellent color vision, and often employ bright colors and striking patterns to attract mates. Some artists have taken this concept to the extreme: See the almost day-glo colors employed by Luis Rey. All of this falls within artistic license, though even this bastion of dinosaur mysteries may disappear for some species. Actually, color can be preserved in fossils, and several recent studies have applied this to fossilized feathers, like those found on some dinosaurs.

Above: One of the iridescent feathers studied by Prum and colleagues in the new paper, discussed below. From National Geographic.

Fossils preserving life body patterns or even color are not new. Many fossilized fish and insects have preserved patterning or even hints of iridescence in their wings, shells, and scales. At least one ammonite fossil is even said to preserve the original, blood red coloration, possibly indicating a deep-sea habitat due to similar color in modern animals from that environment.

A new technique has been developed to help determine if color patterns are real or due to preservation. A 2008 paper by Jakob Vinther and colleagues described looking at apparently patterned fossil feathers under a microscope, looking for (and finding) melanosomes, the remnants of pigment present in life. The traditional view held that most fossil feathers which are preserved as dark 'stains' in a halo around the fossil are caused by bacteria, which cover the feathers as they decay. Vinther and colleagues found fault with that interpretation, though. For example, some fossil feathers show both dark and light bands in regular patterns. Why would bacteria only be present in such regular segments of fossil feathers? Vinther reckoned that rather than bacteria, the small nodules associated with these bands and dark spots (seen under a microscope) were pigment cells, and represented the actual dark/light patterning (though not the specific color) that would have been present in the living animal. Vinther and colleagues concluded that in fact almost all fossil feathers are preserved this way.

Above: Figure 1 from Vinther et al. 2008, showing melanosomes preserved in a banded fossil feather.

That's not to say that feathers lacking a dark carbon film lacked melanin in life--further examination is needed. For example, most specimens of Archaeopteryx do not preserve dark, stained feather impressions. Does this mean the feathers were white? No--in fact, close examination shows impressions where melanosomes would have been, but have since been lost or decayed away.

Still, this could have implications for the famous feathered dinosaur fossils from China. Many of these do preserve feathers as dark carbon stains (presumably caused in part by melanin), and do sometimes show a banded pattern. Such banding can be seen in the tail feathers of Caudipteryx. The "ring tailed" appearance of the holotype Sinosauropteryx tail is probably real, given an unpublished study by Nick Longrich and confirmation (via Dinoforum, of course) that the bands match up across both fossil slabs and so can't be an artifact of splitting the rock as originally suggested. Longrich also suggested that the apparent absence of feathers on the underside of Sinosauropteryx doesn't mean they weren't there, but rather that these feathers were white and did not leave a stain in the rock. Whether or not these feather patterns contain melanin is still an open question that, to my knowledge, nobody has really studied.

Above: Sinosauropteryx may have been counter-shaded, with a white belly and ringed tail. Image from a work in progress digital painting by Matt Martyniuk, all rights reserved.

So, we might actually know what kinds of patterns a few dinosaurs had in life, thanks to preservation of feathers and melanin. But what about actual colors? Well, a new study of melanin in fossil feathers (this time from the Eocene Messel deposits of Germany, home of Darwinius) has found that even traces of iridescence and life color can be recovered. In the future, more detailed study of dinosaur feathers might reveal something similar. A few barely-published specimens of Microraptor do have a very beautiful blue sheen to them (see photo above). Preservation artifact, or dromaeosaurid Blue Jays?

Luckily, formal evaluation of the feathered dinosaurs using this technique is in the pipeline. As co-author of the study Richard Prum told NatGeo, "We are eagerly hoping to be able to work on some of the Chinese dinosaur feathers to try to reconstruct the colors of the feathered dinosaurs." So, the days of drawing these dinosaurs with whatever day-glo magenta stripes you like may be over.

Above: Tail feathers of Microraptor specimen TNP0099624, from figure 2 in Xu et al. 2003. Could these show the color in life or iridescence? Future studies will find out.

And does anybody else remember that very old bit of goss from the DML about a Velociraptor specimen with associated feather proteins that could reveal the color...?