Your bill's looking a little puny, there, buddy. (Painting by Heinrich Harder, 1912, public domain).

Everybody knows Pteranodon. Quick, stop to imagine it! It's easy, because it's the most often-illustrated and well known pterosaur to the general public (though today's marketing departments often call it a pterodactyl, following it's original, century-out-of-date classification).

But hold on. That image you have in your head right now, of a big pterosaur with a long crest and a mid-length pointy beak? That's likely wrong, and may be just as much a hybrid as those Flintstones-style creatures with pteranodont crests and Rhamphorhynchus tails.

How do we know? Let's talk about Dawndraco.

There's a dinosaur game in development called Saurian. Have you heard of it? You should really check out! It's shaping up to be super cool and extremely rigorous when it comes to science and coming up with accurate portrayals of an extinct ecosystem. Check out their page!*

*Full disclosure: I may be involved in this game's development in some small capacity. There will be birds.

The Saurian developers have made a somewhat controversial choice when it comes to the name of the Hell Creek Formation hadrosaurid. Yes, boys and girls, a video game company has dipped its toe into the boiling caldera that is dinosaur nomenclature.  Many fans (and keep in mind these are people who know enough to be early backers of a game priding itself on scientific accuracy and technical minutiae) were a little shocked to see the announcement of the Saurian hadrosaurid. Not just at the unbelievably painstaking level the devs went to in order to research and create the character - everything from life history and growth trajectories to mapping out the actual pattern of scales found on an infamous fossil mummy. People were also a little put off by the fact it was named Anatosaurus annectens rather than Edmontosaurus annectens.

I'm not going to re-hash the long and convoluted history of everybody's favorite "trachodont" (Wikipedia does a pretty good job of that). For the purposes of this post, it's enough to understand that these two species of dinosaurs, Anatosaurus annectens and Edomontosaurus regalis, are fairly similar. So similar that for the past 25 years or so, most scientists have "lumped" them together under the same group of species, the genus Edmontosaurus, making the binomial of the Hell Creek Formation species Edmontosaurus annectens and relegating the name Anatosaurus to the trash heap of history.

But, a few years ago something changed. See, there was a second Hell Creek hadrosaurid, a bigger and much more different looking beast named Anatotitan copei. During the same 25 year period, mostly everybody has agreed this dinosaur was different enough from its relatives to deserve its own genus name. Recently, studies have demonstrated that those differences aren't necessarily due to being more distantly related, but just being... older. Anatotitan, it turns out, is just a mature version of Anatosaurus/Edmontosaurus annectens that had built up more unique features with age. It's not just a similar species to annectens, like Edmontosaurus reglais is, it's the same species. So onto the trash heap with Anatotitan.

But wait! Anatosaurus was thrown out because it was too similar to Edmontosaurus. Now, it turns out, it was actually different--different enough that its adult form was given its own genus for all those years. So shouldn't Anatosaurus be a genus again?

Well, that depends on what you mean by "genus". There is no universally recognized rationale for what makes something "different enough" to be a genus, and the concept varies wildly between fields of biology. Each scientist has their own opinion, their own gut feeling based on tradition and intuition, not science, of what a genus should be. If you asked an entomologist to re-classify all dinosaurs based on her own personal "genericometer" settings, we'd end up with one single genus of dinosaur, and it would include every bird that ever lived. Probably crocodiles too. We'd be left arguing, based on page priority or something, if the star of Jurassic Park should be called Passer rex, Vultur rex, or Crocodylus rex. On the flip side, if you had a ceratopsian worker reclassify the beetles, we'd end up with a hundred billion new genera of beetle.*

*I'm not 100% sure that's the correct number, but it'd be something with a lot of zeroes.

Some people have attempted to bring some science to the art of taxonomy, and quantify genera. Recently and most famously, Emanuel Tschopp and colleagues published their precise genericometer settings, and used those settings to reclassify the diplodocid sauropods. This resulted in bringing back the old, previously-junked genus name Brontosaurus (you may have heard of it). This is a great thing to try, but the method was only designed to apply to diplodocids. It might wreak havoc with names in other dinosaur groups, and would certainly result in an entomologist revolt if anybody ever tried to use it on bugs.

To their credit, the Saurian team have been up front with their genericometer settings used in the game. Rather than base their concept of genus completely on anatomical similarity, they've made the very intriguing choice of combining evolutionary relationships with a chronological component. Basically, if species B is the closest relative of species A, and if species B is known from fossils that can be dated to within one million years of species A fossils, then species A and B are to be classified in the same genus.

I thought it would be fun to try out these genericometer settings and see how it compares to the current traditional consensus, and to some other more widely criticized attempts to re-genericize dinosaurs, like the classification used by Greg Paul in his Princeton Field Guide to Dinosaurs.

Edmontosaurus vs. Anatosaurus.

We'll start with Anatosaurus. If we take Anatotitan to be its synonym, then according to most recent phylogenies, its closest relative is Edmontosaurus regalis, which lived more than a million years earlier. This is why Saurian chose to split Anatosaurus back off into its own genus. But right here, we immediately need to note how highly dependent on the vagaries of phylogenetic analysis this method is. Ugrunaaluk is a very similar hadrosaurid that actually lived in between Edmontosaurus and Anatosaurus, and was originally thought to represent specimens of Edmontosaurus. According to the (very few) phylogenetic analysis on its relationships, Ugrunaaluk is actually outside the Anatosaurus+Edmontosaurus clade. But, given its chronological position, it's always possible more analysis will show that it is transitional between them. Ugrunaaluk is still too old to connect Anatosaurus to Edmontosaurus by a million years or less, but only slightly. Ugrunaaluk lived about 69 Ma ago, and the earliest Anatosaurus fossils are about 67 Ma old. All it would take would be one slightly younger Ugrunaaluk specimen, in that case, to pull the whole shebang back into Edmontosaurus.

Following this cladogram for the sake of argument, let's look at the next outgrip to Edmontosaurus, which is the clade Saurolophini. Now we reach the sticky question of what counts as the next closest relative of Edmontosaurus, moving down the tree. So lets start at the tip of the next branch, with Saurolophus. S. osborni lived between about 69-68 Ma ago, slightly later than the last Edmontosaurus, but still within a million years. S. angustirostris lived about 70 Ma ago, during the time Edmontosaurus was alive. Prosaurolophus lived up until around 74 Ma ago, which predates Saurolophus but sits just barely within a million years of the lower range of Edmontosaurus. Since both Saurolophus and Prosaurolophus lived within a million years of the upper and lower range of Edmontosaurus, following these genricometer settings, they should all be lumped into a single genus. Because of the rules of priority, that means Edmontosaurus itself goes on the trash heap and Saurolophus regalis becomes the correct name for that species. Same for the next closest relative to the Saurolophus + Edmontosaurus group, Gryposaurus, which is within a million years of Prosaurolophus. Ditto Kritosaurus. It's not until the Brachylophosaurini clade that we finally get a break from all this lumping, but already, half of the short-crested hadrosaurids are now Saurolophus.

Obviously, I'm taking this a little far on purpose, just to test it out as a general-use genericometer for dinosaurs. You could easily tweak these settings to produce more traditional genera, like adding a rule against paraphyly (both Anatosaurus and Kerberosaurus would fall within a clade formed by members of Saurolophus in the above example; though in my opinion this is a feature rather than a bug, since some genera had to have evolved from others anyway, it's a little silly trying to rigidly keep them monophyletic). We could also add a stipulation that the time component is relative to the type species or, even better, type specimen, to allow for inevitable evolutionary grades from one form to another. This would, in effect, place a sort of million-year "radius" around a species that is not ever-expanding. So anything up-tree or down-tree of E. regalis, like Ugrunaaluk, gets caught in its gravity well, but we don't then jump to anything within a million years of Ugrunaluuk, too. I have to think this is probably the real intent of the Saurian team's method.

A variety of ceratopsid genera, by Danny Cicchetti (CC-By-SA). "These are all different GENERA? That's hilarious," --Entomologists.

Using this type-restricted genericometer method could still do some fun things in the one part of the dinosaur tree that everybody sort of secretly thinks is horribly over-split but doesn't say so out loud because nobody really wants to rain on those guys' big ol' naming party: the ceratopsids.

The Saurian team stated that, if they were to include Torosaurus as a distinct species in the game, it would be as a species of Triceratops, per the genericometer settings described above. Following this cladogram and a type-restricted interpretation of Saurian's method, Torosaurus does become a species of Triceratops, the holotype of which is from about 67 million years ago. Nedoceratops has to go as well. Now, the Triceratops party ends there based on this particular cladogram, but I find the placement of the Titanoceratops a little er... iffy. Titanoceratops is really, really similar to Pentaceratops from almost the same time and place, so finding it in between a bunch of species that look basically identical to Triceratops is odd. I'm not saying it's wrong, but let's just ignore it for the moment. If we do, then Ojoceratops, Eotriceratops, and Regaliceratops all become species of Triceratops, too. So the entire clade Triceratopsini = Triceratops.

Further down the tree, we have Anchiceratops and Arrhinoceratops becoming synonyms. Kosmoceratops and Vagaceratops, too. Chasmosaurus subsumes Mojoceratops, Agujaceratops, Utahceratops, and Pentaceratops. Coahuiloceratops and Bravoceratops are both safe, and form the sister clade to the big Chasmosaurus complex.

On the centrosaurine side of the tree, Achelousaurus becomes Einiosaurus, unless paraphyly is invoked. Centrosaurus gobbles up Coronosaurus, Spinops, and Styracosaurus (again, unless paraphyly is invoked, in which case Styracosaurus remains valid but includes Rubeosaurus ovatus; this was the plan for one of the unmet Saurian Kickstarter stretch goals that would have included Styracosaurus ovatus).

Overall, this system produces a classification that is similar to, but not nearly as extensively lumped, as the one used by Greg Paul. I kind of like it, especially with the type species stipulation in play. I think that if you are going to use genera, and not just convert all genus names to species praenomen as some people have suggested, it's a good idea to have some kind of standard metric. The problem is, of course, that nobody will ever agree to one standard. Even within dinosaurs. Nobody specializes in all dinosaur groups. We have ceratopsian workers, tyrannosaur workers, avialan workers, sauropod workers, etc., all with their own traditions and personal metrics. This is why it tends to be the science popularizers, like the Saurian devs or Greg Paul or even Bob Bakker, who are the ones coming up with what all the professionals view as highly idiosyncratic classifications. They're attempting to take all these disparate fields within dinosaur paleontology and apply a single metric to all of them, which is bound to change a few things away from the consensus.

At the end of the day, the consensus is what it is. I'm glad people are exploring ways to apply consistency and standards to science-related minutiae like taxonomy. But it's equally important that those efforts be transparent, so we can compare each metric to the others and see which produces the results we like the best. Because at the end of the day, all of this splitting and lumping of genera comes down to just that: a matter of opinion.

Life restoration of an advanced stegosaur- I mean an ankylosaur (Ankylosaurus magniventris) by Emily Willoughby,  CC-BY-SA.

When digging into the history of North American fossil interpretation for the eventual next edition of my Beasts of Antiquity series, one thing that I found a bit weird was the constant reference to ankylosaurids and nodosaurids as types of stegosaurs. To a modern reader, this seems off. After all, the group of armored dinosaurs, Thyreophora ("shield bearers"), is divided into two major groups: Ankylosauria and Stegosauria, each with a few well supported subgroups. It makes sense that these close relatives might once have been classified together, and stegosaurs were discovered first, lending them priority of name. But what changed? Neither ankylosaurs nor stegosaurs are particularly large groups (especially the stegosaurs), and it seems odd that 20th century taxonomists would want to raise a group as small as the modern idea of Stegosauria to the level of "suborder".  Why were ankylosaurs eventually spun off, leaving the more primitive stegosaurs behind? I decided to do a little digging to find out.

Brontosaurus excelsus - the triumphant return. By M. Martyniuk, all rights reserved.

By now, anybody who's interested in paleontology, and their mother, and their great uncle, have probably heard the news: Brontosaurus is back!

Of course, the more technically minded paleo fans will know that Brontosaurus never actually went anywhere. Ever since its first specimen was studied in 1879 by Bone Warrior O.C. Marsh, paleontologists have agreed that the species Brontosaurus excelsus* was unique among sauropods. The question soon became, however, exactly how unique. In 1903, Elmer Riggs decided that it was similar enough to another sauropod species, Apatosaurus ajax, that they should both be placed in the same category of sauropods, and since Apatosaurus was an older category ("genus") name than Brontosaurus, he reclassified the species as Apatosaurus excelsus. However, it was clear even to Riggs that Apatosaurus excelsus and Apatosaurus ajax were different species, and the decision to "lump" them together into one category was always subjective and non-scientific - these kinds of things are a matter of taste only.

It's not often that we are introduced to a large new clade of stem-birds*, but a new paper by Wang et al. finds support for just such a thing among the enantiornithes. Named Bohaiornithidae, the family unites a few previously-known similar-looking opposite birds with two brand new species.

Phylogeny of Bohaiornithidae, modified after Wang et al. 2014.

In a previous post, I hung my tentative re-identification of the holotype teeth of Deinodon horridus on a rough correlation between the Judith River and Oldman formations, the latter of which is more precisely dated and, more importantly, contains Daspletosaurus torosus, which is a candidate for the owner of Deinodon teeth.

While researching a different topic, I stumbled across a more definitive published correlation of these two formations I wasn't previously aware of. In their 2001 paper on the stratigraphy of the Two Medicine Formation, Horner et al. discuss the correlation of parts of that formation with the Judith River. Horner et al. note that the Judith River can be separated into two basic units divided by a disconformity, corresponding with a marine transgression (when the terrestrial ecosystem was swamped by the rising of the Western Interior Seaway, the sediments deposited by which appear to have been lost in this instance).

Helpfully, Horner et al. note that it is from the lower unit that Hay collected numerous dinosaur teeth which were later described by Leidy as the infamous tooth taxa such as Deinodon, Aublysodon, Trachodon, and Troodon. More helpful still, the paper provides a handy chart showing the arrangement of the strata and including points at which radiometric dates have been taken. The base of the lower Deinodon-bearing unit is dated at about 78 million years old. The next available date is from just above the disconformity (i.e. after the seaway had retreated again) and shows an age of 75.4 million years ago. That's narrowing it down, but there's no date from within the formation from just below the disconformity, which would give us an upper boundary for the Deinodon strata.

But, there's hope. Horner et al. note that Rogers (1998) suggested the disconformity itself probably correlates to around the Willow Creek Anticline in the middle Two Medicine Formation (which contains the famous Egg Mountain Maiasaura nesting site). This segment of the TMF has been dated to 76.7 Ma ago, which may give us a rough upper boundary for the age of Hay's fossil tooth collection.

So, based on this paper at least, it looks like Deinodon and friends were collected from rocks aged somewhere between 78 and 76.7 million years old. Which is about the same age range as the Oldman Formation to the north. So, Deinodon horridus and Daspletosaurus torosus did indeed live at about the same time and in the same region (there were no checkpoints at the US-Canadian border back then!), making it more likely that they represent the same species, and the possibility that Deinodon actually represents Gorgosaurus less likely.

Looks like I'm going to have to create a new tag for Arcane Biostratigraphy and Geology Stuff...

Oh, and somebody in the comments last time asked me to get into Trachodon. This is definitely a subject for a longer blog post, though I'm a bit less excited about it because I'm more pessimistic that it's identity is knowable. But maybe this new info can help us get started. I already mentioned that the Trachodon teeth appear to come from the same strata as Maiasaura (and it's well known that Trachodon's contemporary Troodon formosus is reported from Egg Mountain as well, though T. formosus is also reported from pretty much everywhere and everywhen else...). Could Maiasaura be Trachodon? Perhaps! But it could also be Brachylophosaurus, or maybe even Gryposaurus. And... there's been a rumor going around for a while now that Trachodon teeth are referable to Lambeosaurinae. Which lambeosauines are known from this time and place that could fit the bill? Both Parasaurolophus and Corythosaurus have been reported from the uppermost Oldman, though these may be too young. Hypacrosaurus sp. seems to have been contemporary with Maiasaura, so that could be it...

Yeah, you can see why I'm pessimistic. Tyrannosaurids are rare, and there tend to be only one or two species of tyrannosaurids present in any given ecosystem. Hadrosaurids are... the opposite.

References

Horner, J. R., Schmitt, J. G., Jackson, F., & Hanna, R. (2001). Bones and rocks of the Upper Cretaceous Two Medicine-Judith River clastic wedge complex, Montana. In Field trip guidebook, Society of Vertebrate Paleontology 61st Annual Meeting: Mesozoic and Cenozoic Paleontology in the Western Plains and Rocky Mountains. Museum of the Rockies Occasional Paper (Vol. 3, pp. 3-14).

My recent illustration of a specimen traditionally assigned to Gorgosaurus was labelled Deinodon, usually considered a likely synonym. But is it really? Deinodon is, in fact, much more likely to have been Daspletosaurus all along. Read on for the nitty-gritty stratigraphy!

Reconstruction of Didanodon altidens specimen ROM 794 (aka Lambeosaurus lambei, aka Procheneosaurus praeceps) by Matt Martyniuk, all rights reserved.

I've talked a lot on this blog about my personal justifications for using "old fashioned" names for many groups or species of stem-birds. In many cases, names which were in common use during the 19th and early 20th centuries were replaced later by one or two influential scientists for reasons which don't really hold up when you look at the codes that govern naming in biology. For example, Manospondylus gigas may currently be the correct name for the theropod we know and love as Tyrannosaurus rex, but this possibility has almost never been discussed because everybody assumes it's a nomen oblitum - a name out of use for so long that it becomes automatically invalid under the International Code of Zoological Nomenclature (ICZN). Note the word "assume"--as I've written before, most people, even working scientists, don't really know what criteria must be met to classify a name as obsolete.

The name of one very well-known dinosaur is in such a sorry state that it's like the Manosponylus / Tyrannosaurus debacle squared. The genus Lambeosaurus, a well-known hadrosaurid with a distinctive squared-off crest with a backward-pointed prong, was named twice prior getting its popular moniker, and neither of those names can be considered obsolete, since they were both coined during the 20th century.

The first name given to fossil material (in this case a jaw) now universally attributed to Lambeosaurus was Didanodon. In a 2006 review of hadrosaurs, Lund and Gates stated (without discussion) that the genus and its type species, Didanodon altidens, were nomina nuda, or "naked names" lacking the proper description necessary to establish them. But is this really the case?

Hypothetical restoration of an adult Monoclonius crassus, by Matt Martyniuk. All rights reserved.

Skull of the subadult Monoclonius lowei. Note the three prominent projections at the rear of the  parietal frill. Incipient styracosaur-like spikes?

Type specimen of D. cuhe, originally posted by Andrea Cau

I'm interrupting my regularly scheduled upcoming blog posts to bring some attention to a little-known Jehol bird: the strange 'jeholornithid'-grade species Dalianraptor cuhe.

D. cuhe has spent the last several years as a species in obscurity, even among most paleontology enthusiasts. I recall my first glimpse of the type specimen, wondering over the seemingly-complete remains of an "undescribed possible dromaeosauird" in a low-res photo posted online in the early '00s. I can remember saving the image to my reference folder, hoping that one day I'd be able to update the file name. It's a fascinating animal, but... is it real?

Fossil tail feathers of S. cooperorum, from O'Connor et al., 2009.

As a follow-up to last month's post on the smallest Mesozoic theropods, here are a few additional observations on the small longipterygid Shanweiniao. Like other longirostravisines*, Shanweiniao cooperorum had reduced "hands" entirely lacking claws. This reduction of wing claws seems to have occurred independently of modern birds within this uniquely specialized group of enantiornitheans. (Euornitheans seem to have lost the bulk of their wing claws around the level of Carinatae, though many modern birds still retain at least keratinous claws on their wings, and longirostravisines may have as well).

S. cooperorum itself is most well-known for its elaborate tail made up of six ribbon-like feathers. Those feathers overlapped at the base, and may have acted as an air brake for precise landings with the feet on small branches. It's possible that most other enantiornitheans, which lacked long feathery tails and also retained wing claws, landed by simply smacking clumsily into tree trunks or brush and grabbing on with all four limbs.

Enantiornis leali was among the first enantiornithes to be found, and the first to be recognized as a member of a unique lineage of "opposite birds" separate from modern birds (Gobipteryx minuta, now recognized as an advanced enantiornithe, was found earlier). But despite being such a widely recognized and historically important member of its namesake group, little can actually be said about this species in terms of ecology or life appearance. Of course, that can't stop us from trying to figure out as much as we can by examining the available evidence and ecological context of these long-dead birds.

For those who didn't figure it out, yesterday's mystery bird teaser was a bit of a trick question. In fact, the bird, which I restored on a lark when working on other species, never existed at all. It was, in fact, a restoration of the famous fossil chimera, "Archaeoraptor liaoningensis". Two commentors did get it half right, guessing Yanornis, though the long tail would make that identification impossible (as euornithines, Yanornis had short tails with retractable fans of feathers). You'll notice I modified the image a bit since yesterday: Mickey Mortimer pointed out that Yanornis were not fully toothed, and while the premaxilla had teeth, there is a small edentulous anterior portion which may have supported small beaks.

Despite being the most famous fossil forgery to come out of China, the "Archaeoraptor" debacle really is a success story for the peer review process. You can read a summary of the history of the specimen here. The upshot is that several researchers were suspicious of the chimeric specimen to begin with, and though they rather dubiously chose to submit it for publication anyway, their paper was subsequently rejected by two major journals, Nature and Science, before unfortunately being reported on without review in National Geographic magazine.

In fact, it's not surprising that so many researchers were suspicious of the specimen's validity to begin with. At it combines the skull, body and wings of a Yanornis martini (a songlingornithid euornithine) and the tail of a Microraptor zhaoianus (a microraptorian dromaeosaurid), the "Archaeoraptor" specimen would have been a very odd anomaly had it been real, given our knowledge of bird evolution (even in 1999, when it was first revealed to the public). Note that many news reports have stated that the hind limbs of the composite specimen also come from a Microraptor or even a third, unidentified type of bird, Zhao et al. (2002) noted that they also come from a Yanornis martini. Anyway, I broke out Professor Farnsworth's What-If Machine to try to suss out how our current understanding of bird evolution would be different if the composite nature of the original "Archaeoraptor" specimen had never been discovered.

Intuitively, it seems like a bird with the long tail of a dromaeosaurid combined with the advanced wing configuration and well-developed breastbone of an euornithine doesn't make much sense and would have eventually caused a rather extraordinary rearrangement of the bird family tree. To test this idea, I employed the services of phylogeneticist extraordinaire Mickey Mortimer, who had coincidentally just finished coding Yanornis martini and entering it into a combined Theropod Working Group matrix. Mickey very helpfully humored my request and combined the relevant anatomy Yanornis and Microraptor into a single taxon, and plugged the result into a theropod phylogeny which included only other taxa known in 1999.

I'll let Mickey explain the analysis in more detail:

"Okay, so what I've done is taken my Theropod Working Group analysis and restricted it to taxa described by 1999 (when "Archaeoraptor" was supposed to be described) and coded by the TWG [Theropod Working group - Ed.] by 2005.  I've also limited it to those characters taken from the first TWG analysis (Norell et al., 2001), since I already posted those results on my blog (http://theropoddatabase.blogspot.com/2011/06/theropod-working-group-matrix-recoded.html) and Scott understandably doesn't want more of the Lori results being distributed before publication [Click here for the scoop on Lori, Scott Hartman's unpublished Morrison troodontid -Ed.].  So data-wise, this is equivalent to results I've already posted and with the exception of new specimens of old taxa (like the new Caudipteryx specimens in Zhou et al., 2000), which would be far too tedious to correct for, is representative of our knowledge in 1999.  "Archaeoraptor" is represented by the Yanornis codings mixed with Microraptor tail codings.  Many of those Yanornis codings are from specimens besides the Archaeovolans holotype, but I'm not going to take the time to go through and see exactly which characters can be coded from only that specimen.  In total, 11 codings were changed between Yanornis and "Archaeoraptor".  The entire matrix is 51 taxa and 210 characters."

The result of Mickey's analysis was that "Archaeoraptor" ended up as the sister taxon to Confuciusornis, but with some caveats. First, no other pygostylians (the group uniting Confuciusornis and modern birds)were included, because Confuciusornis is the only pre-1999 taxon coded by the TWG. A complete test of "Archaeoraptor"'s 1999 relationships would require the addition of taxa like Patagopteryx, Songlingornis (which is a potential close relative of Yanornis), Cathayornis, Iberomesornis, etc. Because the only plesiomorphic character of "Archaeoraptor" relative to Yanornis and other euornithines proper are the "longer tail, elongate distal caudal prezygapophyses and rectangular proximal caudal centra", "Archaeoraptor" looks, for 1999 standards, like what we might have expected the sister taxon of Pygostylia to be like. Nevertheless, because the bulk of the specimen is so derived, Mickey reckons the presence of the long tail might not pull it away from euornithines even if other basal pygostylians were included (the long tail would then have to be considered a bizarre reversal).

Mickey also tested a few alternate hypotheses to see how much support they would get. Perhaps the obvious conclusion for a scientists faced with an oddity like "Archaeoraptor" would be that it is probably a sister group to Pygostylia as mentioned above, or somehow intermediate between dromaeosaurids and pygostylians. Mickey tested this by forcing "Archaeoraptor", Confuciusornis, and dromaeosaurs to clade together, which resulted in only three extra steps: this would have been considered a pretty sound hypothesis given the small pygostylian sample. Interestingly, this arrangement would also have resulted in unenlagiines as basal eumaniraptorans and put Archaeopteryx in Troodontidae. Removing "Archaeoraptor" from the mix decreased the likelihood of a Dromaeosauridae+Pygostylia clade by five steps, which Mickey notes is still "plausible" but certainly less likely, and shows that "Archaeoraptor" would have created the kind of link between dromies and more advanced birds touted by the original NatGeo article.

This leads me to speculate that "Archaeoraptor" may have provided "evidence" for the  modular evolution of pygostylians directly from some traditional dromaeosaurs. Modular evolution refers to cases where major traits of a descendant group appear in a taxon which simultaneously retains major "primitive" or plesiomorphic traits of the ancestors taxa. One famous fossil example of this phenomenon is Darwinopterus modularis, which is a long-tailed pterosaur with a generally primitive, "rhamphorhynchoid" body plan, but which has a characteristically pterodactyloid-type skull. Had "Archaeoraptor" been accepted as real, we may now have believed that characteristic euornithine traits evolved first in the skull, forelimbs and torso of taxa which possessed otherwise dromaeosaurid tails (this is almost the exact opposite of how we view bird evolution today, with tail shortening coming very soon after the split between dromaeosaurs and pygostylians). As Mickey found, without more discoveries of basal pygostylian and ornithothoracine birds, our cladograms may have rendered dromaeosauridae paraphyletic with respect to modern birds.

Ok, but how would all this stand up over the years after 1999, with more and better specimens of basal birds from a variety of lineages? From Mickey:

"Here's where I'd expect the inclusion of more pygostylians to have an effect though, since right now with only Confuciusornis, "Archaeoraptor" is effectively the most basal pygostylian.  But if we had an omnivoropterygid, an enantiornithine, and other ornithuromorphs in there, Yanornis' birdy characters would nest it with those and make its dromaeosaurid-like tail a reversal."

So, the discovery of more and better basal bird specimens may have been enough for "Archaeoraptor" to be regarded more and more as a curious side-branch of the avian family tree, less and less relevent to bird evolution as a whole: a euornithine with some rather inexplicable reversals. This would be similar to the way the relevance of the Piltdown Man to human evolution was exponentially reduced by numerous valid specimens before it was finally found to be a hoax.

It wouldn't be DinoGoss without a discussion of taxonomical minutiae, and this is a question that has popped up on the net several times before: if "Archaeoraptor liaoningensis" included the holotype specimen of Microraptor zhaoianus, why isn't the former an objective senior synonym (that is, a name that is synonymous by virtue of being based on the exact same specimen, not a different specimen later assigned to an already named species) of the later?

The crux of the argument is that the original National Geographic article that released the "Archaeoraptor" name did not satisfy the criterion for publication set forth by the International Code of Zoological Nomenclature (ICZN).The article, "Feathers for T. rex", was written by Christopher Sloan for the November 1999 issue of the magazine. While Sloan did technically coin the name "Archaeoraptor liaoningensis" by publishing it in a widely-distributed magazine (and the ICZN does not mandate that names can only be created in peer-reviewed journals), he did not make it clear that he was intending to formally erect a new taxon (usually done by specifying ("new genus and species", "gen. et sp. nov.", or some variation). Furthermore, he explicitly referred to the fact that a formal description of the species was forthcoming. Most observers have interpreted this as falling short of the ICZN requirements for naming taxa, and I don't know of any good reason to disagree.

A more complicated factor is that, among the subsequent publications on the chimeric fossil, some authors did try to formally name the taxon and designate a lectotype (when a type specimen is found to actually represent two or more individuals, a lectotype must be chosen from among them to officially bear the name that originally applied to the lot). Noted BANDit Storrs Olson published an article in a 2000 issue of the Backbone newsletter of the US National Museum of Natural History in which he attempted to remove the tainted name from his own area of study, fossil birds. This is before many BANDits (the "birds are not dinosaurs" crowd) collectively reversed their positions and decided that dromaeosaurs ARE fossil birds after all, thus becoming MANIACs ("maniraptorans are not in actuality coelurosaurs"). Olson therefore designated the tail specimen as the lectotype. This would seemingly make "Archaeoraptor" the official senior synonym of Microraptor.

Not so fast. Olson did not actually describe the specimen or convey intent to coin the name. Like Sloan, he referred the creation of the name to other authors (in this case, Sloan himself, in the mistaken belief that Sloan's article DID coin the name). So Olson effectively specified that the nomen nudum "Archaoraptor" should refer to the tail, but failed to officially create the name, let alone specify its lectotype.

And that is why "Archaeoraptor liaoningensis" remains a nomen nudum; at least, just until some cheeky bastard decides to formally attach the name to something for reals. Technically, nomina nuda are still up for grabs nomenclature-wise...

A gorilla is a type of primate. The gorilla is a primate. Gorilla is a primate. Gorilla gorilla is a primate. Hominidae is a group of primates. We use such oddly varying ways of talking about taxa. Image by Pierre Fidenci, licensed.

Recently, an illustration of an Allosaurus was selected as an upcoming picture of the day at Wikipedia. Before going live, the POTD folks asked the article editors to suggest improvements to the caption they had written (based on the text already in the Allosaurus article, which is a featured article at Wikipedia and thus thoroughly checked for errors). Here is the original caption written by the POTD editors:

"An artist's rendition of the gape of an Allosaurus species of dinosaur, based on the research of paleontologist Robert T. Bakker. Allosaurus was an active predator of large animals, and had the ability to open its jaws extremely wide. Studies suggest that it used its skull like a hatchet against prey, attacking open-mouthed, slashing flesh with its teeth, and tearing it away without splintering bones."

The obvious error there is that it describes Allosaurus as a "species of dinosaur" when it is in fact a genus. So, just change the first sentence to "An artist's rendition of the dinosaur genus Allosaurus" and it's fixed, right? Pretty much any science writer or paleontologist you talk to would say yes. The following was proposed as a correction:

"An artist's rendition of the dinosaur genus, Allosaurus, with it's jaws open fully, based on the research of paleontologist Robert T. Bakker. Allosaurus was an active predator of large animals, and probably had the ability to open its jaws extremely wide. Studies suggest that it used its skull like a hatchet against prey, attacking open-mouthed, slashing flesh with its teeth, and tearing it away without splintering bones."

But isn't there a problem with referring to a genus in the singular that way? Though many dinosaur genera are monotypic, a "genus" is still technically a group of animals, no different from a "family" or an "order." Let's re-write the same caption, but replace Allosaurus with Allosauridae:


"An artist's rendition of the dinosaur family, Allosauridae, with it's jaws open fully, based on the research of paleontologist Robert T. Bakker. Allosauridae was an active predator of large animals, and probably had the ability to open its jaws extremely wide. Studies suggest that it used its skull like a hatchet against prey, attacking open-mouthed, slashing flesh with its teeth, and tearing it away without splintering bones."

This caption obviously makes little grammatical sense, because we  intuitively recognize that the family Allosauridae is collective (despite the fact that, like the genus Allosaurus, it is usually thought to contain only one species). But the genus Allosaurus is also collective, and for that matter, the species Allosaurus fragillis is a collection of populations and individuals.

But these strange constructions are nearly universal in science writing, including (especially) formal science writing. In a way, this is a bit of an archaism. Think of the archaic-sounding phrasing in some old children's books, like "Tyrannosaurus: he was the king of the dinosaurs! His mortal enemy was Triceratops." Referring to an entire genus as a "he" ties into the anthropomorphic "roles" we assign dinosaurs ("Tyrannosaurus: he's a bad guy. Triceratops: he's a good guy). Mark Witton has previously written about this effect here. Similarly, referring to genera or even species in the singular places them in the same league as Godzilla: single, towering, fantastical monsters, rather than categories of normal animals.

Referring to an animal as "the this" or "the that" is a another archaism."The Tyrannosaurus was the dominant predator of his time." "The gorilla is the largest living primate." This is more correct than some of the other examples, but also strikes me as stodgy and archaic. Here's a quote from a 1985 paper: "The gorilla is more closely related to man than the chimpanzee is". Wouldn't "gorillas are more closely related to humans than chimpanzees are" seem more suited to the 21st (or even 20th) Century?

But Tyrannosaurus is not that animals' name. It's the name of that animals' genus, the group which contains it.That animal is "a" Tyrannosaurus, it is not the genus Tyrannosaurus itself. Alternately, it is "a tyrannosaur", but it is not simply "tyrannosaur." Using lowercase "common names" is one easy solution, but one that can create a different kind of confusion. Is a "tyrannosaur" a Tyrannosaurus or any tyrannosaurid? Is Daspletosaurus a genus of tyrannosaur? This isn't a perfect example because there's no group named "Tyrannosauria", at least not yet. But think of how we use "dinosaur" instead of "dinosaurian", when it could just as easily be referring to the genus Dinosaurus. One solution would be to use such common names the way we do for living animals: common name followed by clarification. "This is a picture of a tyrannosaur (Tyrannosaurus rex)." "That is a picture of a tyrannosaur (Daspletosaurus torosus)."

Here's my take on the example caption, using a more precise way of conveying the same ideas:

"An artist's rendition of an Allosaurus fragilis with it's jaws open fully, based on the research of paleontologist Robert T. Bakker. Allosaurus were active predators of large animals, and probably had the ability to open their jaws extremely wide. Studies suggest that they used their skulls like hatchets against prey, attacking open-mouthed, slashing flesh with their teeth, and tearing it away without splintering bones."

"An" Allosaurus fragilis: it is an image depicting a member of that species, not an image of the "species" itself. Allosaurus "were" active predators, pleural, because Allosaurus is a grouping of dinosaurs. In my opinion, these slight changes in phrasing give a much more naturalistic feel to the description. It's clear that we're talking about a type of animal in the real world, not enumerating the abilities of an individual Pokemon character.

Isn't it time we put some more thought into how we write about taxa? I think we should be trying to frame dinosaurs as parts of nature, not exceptions to it. Would it be helpful to change the way we talk about taxa, or is the existing method too entrenched and well-understood by those who will obviously know what you're talking about to bother?

Before writing up a big review post for tomorrow, I thought I'd address a request I've gotten a few times, most recently over on my deviantArt page. I've written a few times about old/disused names that have fallen out of fashion in paleontology with little reason (or for reasons that can't really be supported by evidence). In fact, a lot of these 'quaint' or 'old-fashioned' sounding names should really be considered just as valid today as when they were coined.

Now, keep in mind that at least in cases of priority for family-level names, it has been argued that anything goes, because researchers are not necessarily using these names as 'families' under the ICZN but identical clade names that fall under no governing code. In my opinion this is a bit of a cop-out, and a bit hypocritical when espoused by people who would otherwise argue that nomenclature needs to do its best to reduce confusion. I agree with some PhyloCode proponents that, for this reason, endings like -idae should be avoided in clade names at all costs, or at least, those names should be defined in such a way that they roughly correspond to their traditional family name homonyms.

There has been a general tendency in the past few decades to somewhat arbitrarily replace names based on fragmentary taxa with those based on more complete (or simply more famous) taxa. This, again IMO, ultimately negatively impacts stability of nomenclature, despite the fact that many of these 'replacement' names have since come into such common use, coinciding with widespread use of the Internet, that changing them back now gives a false impression of instability. Luckily, some more recent research is beginning to correct a few of these mistakes of recent history. Megalosauroidea (a name based on a fragmentary taxon) had long been replaced by Spinosauroidea (a name based on a different but more apomorphic fragmentary taxon) in the literature, but several recent papers by Benson and colleagues have argued fairly successfully for a reversal of this trend and a return to valid priority.

In a way, it's a shame that the PhyloCode will not give priority to the original author of a name, but rather to the author of its definition, essentially enshrining unjustified replacement names like Coelophysidae in favor of older names like Podokesauridae, robbing the original authors of their rightful credit. It would upset temporary stability (or rather, reverse prior results of instability) but ultimately make more sense to automatically give preference to the older names and their authors, even if they aren't converted to clades immediately when PC goes into effect.

Anyway, here I'll give a brief rundown of some disused names that should still by all rights be considered valid senior synonyms of other names. I'll also throw in a few genera that may have a claim to seniority over more widely used, better known names. Note that this later bit is a completely separate issue--seniority for family-level names is straightforward. At the genus or species level, as I've argued before, often names are ignored as unofficial "nomina dubia". Nomen dubium refers to a name based on a specimen which lacks key apomorphies and cannot be distinguished from two or more similar specimens. However, in many cases I believe stratigraphy itself should be taken into account. If a bone fragment is obviously from a allosaurid theropod, and current evidence only supports the presence of one other such theropod in its stratigraphic level, parsimony dictates they should be considered the same taxon. If and when evidence is found to support the presence of multiple allosaurids in that formation, then and only then can non-diagnostic allosaurid remains be declared nomina dubia.

One more note on nomina dubia: the ICZN does not support the existence of this concept (and as far as I know, neither does the PhyloCode). According to the ICZN, if a type specimen is found to be non-diagnostic relative to more complete specimens, the name should not be ignored--rather, one of those more complete specimens should become the neotype of the oldest available name. So, for example, Deinodon (see below) should not simply be ignored as non-diagnostic relative to Gorgosaurus and Daspletosaurus and then ignored; rather, scientists should have arbitrarily chosen one of those two specimens to become the neotype, removing the validly published name from poor material and leaving the poor material nameless. This is, of course, almost never done, especially among paleontologists, where making sure your name is the one that sticks has historically been a higher priority than eliminating nomenclatural clutter (whether or not scientists who name scrappy material have more of a right to their names to persist than those who describe complete specimens is another story).

Okay, enough of an intro. Here are some old names, and quick examinations of whether or not they should be resurrected:

Families:
Podokesauridae (Huene 1916) is perhaps the classic example of a valid taxon name abandoned for no good reason. In use up until the early 1990s, the name was suddenly changed to Coelophysidae (Nopcsa, 1928) when Holtz and Sereno began to fist include this group in phylogenetic analyses. As far as I know no justification for this was ever given, but I don't have these initial papers to check. At any rate, the type specimen of Podokesaurus has been distinguished from Coelophysis by researchers going back to Colbert in the 1950s, so it is by definition not even a nomen dubium. There is therefore no justification to ignore this name in favor of Coelophysidae/Coelophysoidea etc.

Metriacanthosauridae (Paul 1988) is another case like Podokesauridae where a perfectly valid name based on diagnostic material was arbitrarily replaced by its junior synonym, Sinraptoridae (Currie & Zhao 1994) among most researchers. Nobody doubts the diagnosibility of Metriacanthosaurus as far as I know, and as discussed, this doesn't matter anyway.

Megalosauroidea (Huxley 1869), as discussed above, is a senior synonym of Spinosauroidea (Stromer 1915). Again, Spinosauroidea gained broad acceptance in the early '90s, but several recent papers have been effective in reversing this baffling trend to arbitrarily ignore a widely used name with a history almost as long as dinosaur paleontology itself.

Omnivoropterygidae (Czerkas & Ji 2002) is another case where a once-ignored name is starting to gain traction again in favor of its junior synonym Sapeornithidae (Zhou & Zhang 2006). Both Greg Paul and Tom Holtz have used the correct name in recent popular works, though Sapeornithidae still crops up in the technical literature. This name is an even better illustration of the Czerkas problem. People who favor the junior Epidendrosaurus over Czerkas' senior Scansoriopteryx can at least fall back on the online vs. print publication excuse (though the ICZN is clear and unequivocal on the matter). In the case of this family name (neither have yet been defined as clades), Czerkas' name has 4 years of priority and is still ignored. Let's not beat around the bush--people disagree with Czerkas' conclusions and don't like the way he has (validly if unpopularly) published many of his taxa, and they express this distaste by ignoring his taxonomy. The ICZN has no provision to replace names created by unpopular scientists.

Ornithodesmidae (Hooley 1913) has priority over the better-known Dromaeosauridae (Matthew & Brown 1922). The scrappy type specimen of Ornithodesmus, though initially (correctly) identified as a primitive bird, was soon confused with the much better remains of the pterosaur now known as Istiodactylus. Hooley named Ornithodesmidae as a family of pterosaurs, but it became a theropod family when Ornithodesmus was again recognized as a maniraptoran in 1993. Naish & Martill (2007), as well as Makovicky & Norell (1995), and Mortimer (online) have shown that Ornithodesmus falls into the same family as Dromaeosaurus. So, unless Dromaeosauridae is re-defined to include only Dromaeosaurus and a few closely related taxa (~current Dromaeosaurinae) or trated as a synonymous but differently goverened clade (under the future PhyloCode), Ornithodesmidae has clear priority of name under the ICZN.

Atlantosauridae (Marsh 1877) has clear priority of name over the more well known Diplodocidae (Marsh 1884), and Hay (1902) argued that it has priority over Amphicoelidae (Cope 1877). Atlantosaurus is almost certainly a synonym or close relative of Apatosaurus, and while it may be a real nomen dubium in relation to the various species of contemporary atlantosaurine (=apatosaurine) sauropods, it is definitely a member of this group, and thus higher taxon names should be used accordingly. Even if a taxon is a nomen dubium, there is no reason to change higher taxa names based on it if it can be confidently classified at the 'family' level (as is the case with Ceratopsidae). Again, Atlantosauridae has not yet been defined as a clade, so if Diplodocidae is defined first under parallel systems such as PhyloCode, a situation will arise where Atlantosauridae is valid under one code but not the other--Diplodocidae will be a valid name but for a clade, not a family. Olshevsky (1991) incorrectly labelled Atlantosauridae a nomen oblitum (forgotten name). The ICZN states that to be a nomen oblitum, a name must not be treated as valid in the scientific literature after 1899. However, Atlantosauridae was in use in papers by Steel (1970) and Nowinsky (1971) well into the late 20th Century.

Deinodontidae (Cope 1866) is a slightly more complicated case than the above. It was in clear, widespread use through the mid 20th Century (as in Maleev 1955) and almost always treated as the senior synonym of Tyrannosauridae (Osborn 1905). However, Russel (1970) argued that Deinodontidae be abandoned, because he considered the type specimens of Deinodon (isolated teeth) not diagnostic, rendering the name a nomen dubium. However, the teeth are clearly diagnostic at the family level and possibly even genus and species, as they must have come from either Daspletosaurus or (more likely) Gorgosaurus, and the rocks those dinosaurs come from are well enough sampled to rule out the presence of a third large tyrannosaur species unless such compelling evidence is found. Similarly, it is questionable whether or not the pertinant ICZN rules allow for abandoning a name due to a dubious type genus. Even if this is the case, it is only followed sporadically in the literature, and many family names remain in use that are based on dubious type material, including Hadrosauridae, Ceratopsidae, and Troodontidae (the latter is also based exclusively on teeth of questionable diagnosability at the genus and species levels). Olshevsky (1991) recognized this, but argued that the name is still invalid because Cope initially spelled it Dinodontidae, and the name Deinodontidae was an emended spelling not published until 1914, after Tyrannosauridae. He concluded that therefore Deinodontidae (with an e) is a junior synonym and Dinodontidae (no e) is a nomen oblitum. However, Olshevsky's argument is incorrect because the ICZN clearly mandates that any family names based on misspellings or unjustified spelling changes of their type genus (Cope spelled the name Dinodon) can and must be emended by any subsequent revisor, and that this does not change the original authorship or date of the name (ICZN Article 35.4.1). Also, note that even if Deinodontidae and Deinodontoidea are ignored, several studies have found Coelurus fragilis to be a "tyrannosauroid", and so the next available name for that group after Deinodontoidea is Coeluroidea (Marsh 1881).

Trachodontinae (Lydekker 1888) may have priority over Lambeosaurinae (Parks 1923). As discussed below, the Trachodon holotype teeth may be diagnosible to subfamily level, as some researchers have suggested that they belong to a 'lambeosaurine' rather than a 'hadrosaurine/saurolophine'. If this is the case, even if Trachodon is itself a real nomen dubium (which it probably is), the family name would still carry priority.

Titanosauridae (Lydekker 1885) is, despite being based on a possible nomen dubium, a valid taxon name. However, this situation is complicated for a new reason: the 'family' has proven so large that most researchers now divide it up into several families. If multiple families of titanosaur are used, Titanosauridae itself (but not Titanosauroidea) must be restricted to its dubious type species. This is analogous to the Ornithodesmidae situation described above: if 'dromaeosaurids' were divvied up into several families (Microraptoridae, Velociraptoridae, Saurornitholestidae, Dromaeosauridae), then Ornithodesmidae would still be valid but monotypic, and probably (rightly) fall out of use again.

Hylaeosauridae (Nopcsa 1902) is a senior synonym of Polacanthidae (Weiland 1911), but this is another situation where a name is only valid under certain classifications. Some older classifications placed the group as separate from Ankylosauridae and Nodosauridae, or as a subfamily of either (as Polacanthinae). In these cases, Hylaeosauridae/inae has priority. However, some new studies show the 'polacanthines' the be nested within nodosaurs, and to be possibly paraphyletic. Nodosauridae (Marsh 1890) has priority over both Polacanthidae and Hylaeosauridae, so both names are sunk either way.

This last one isn't a dinosaur group, but is quite an odd situation. As it turns out, Pterodactyloidea (Meyer 1830) has, according to the principal of coordination, priority over the widely-used pterosaur group Ctenochasmatoidea (Nopcsa 1928). Note that this is a different taxon than Pterodactyloidea (Pleininger 1901), traditionally labeled as a suborder. But... they have the same name. This isn't technically a problem because the later Pterodactyloidea, named as a group above the rank of superfamily, is outside any governing code, and practically, nobody uses the superfamily Pterodactyloidea (or Rhamphorhynchoidea, for that matter). But those have priority over other names, which makes them more valid than the suborder name, which can easily be replaced with a new name the way Segnosauria was replaced with Therizinosauria (neither of them governed by the ICZN, so anarchy applies).

Genera and species:
Deinodon horridus (Leidy, 1866) currently appears to be a real nomen dubium, as it is based on deinodontid teeth from the Judith River Formation. I say currently because its status depends on the currently messy taxonomy and stratigraphy of the various specimens/species assigned to Daspletosaurus. Daspletosaurus is not present in the Judith River formation sensu stricto, and is generally known from younger deposits than the chronologically-overlapping albertosaurine species Gorgosaurus libratus. However, specimens that may or may not be Daspletosaurus are known from such a wide temporal and geographic range that it's possible these teeth could belong to it (or a similar tyrannosaurine) instad of Gorgosaurus. Additionally, if it ever is demonstrated to be possible to distinguish between albertosaurine and tyrannosaurine teeth, Deinodon can and should be ressurected to replace one of these two genera. Note that Matthew & Brown 1922 considered both G. libratus and Albertosaurus sarcophagus to fall within the genus Deinodon--this is dependent on subjective lumping vs. splitting (if libratus and sarcophagus are placed in the same genus, and Deinodon=Gorgosaurus, Albertosaurus is also a junior synonym of Deinodon), and ignores the possibility that Daspletosaurus represents the true skeleton of Deinodon. For now, Deinodon must be considered a nomen dubium.

Trachodon mirabilis (Leidy 1856) was named for isolated teeth of a hadrosaur (and some mixed in from a ceratopsian), Also from the Judith River formation. As mentioned above, they may be diagnosable to the level of Lambeosaurinae (=Trachodontinae?). I'm not knowledgable enough about hadrosaurs to know if this species might be currently valid based on stratigraphy. As far as I'm aware, no definite remains of named lambeosaurines are known from the Judith River formation, though this spans a great deal of time and in places overlaps with the Oldman and Dinosaur Park formations of Canada, which contain numerous lambeosaurs at different and better-studied stratigraphic levels. If anybody knows approximately which portion of the Oldman/Dinosaur Park group this part of the Judith River corresponds with, we might be able to find an answer.

Antrodemus (Leidy 1870) has long been recognized as a possible synonym of Allosaurus (Marsh 1877). In fact, I remember making a note 'alos known as Antrodemus' in one of my dinosaur books in the '80s (sticklerism arises early!). As Mickey Mortimer points out on the Theropod Database, Chure (2000) noted that the species of Allosaurus Antrodemus comes from can't be determined, but Chure doesn't consider it a synonym of Allosaurus because it comes from an unknown quarry. I would agree with this, as long as there are multiple genera of allosaurids recognized in the Morrison (i.e. Saurophaganax). If, however, one were to synonymize Saurophaganax and Allosaurus, the name for this genus must then become Antrodemus, no matter how many diagnosable species it contains (Antrodemus valens, the species, would still be a nomen dubium).

I'm sure there are other dinosaurs that could be added to this list, and I may try to do a 'part 2' someday. I've discussed the situations about the Lancian forms Manospondylus, Agathaumas, and Thespesius before.

Stay tuned for something a little less arcane, nitpicky, sticklerish, and taxonomical. The next post will be (gasp!) an unabashedly positive review of possibly the best dinosaur show ever to make it to air.

Making the rounds right now in the media is a story about a newly described, well-preserved baby Tarbosaurus bataar that helps shed some light on the way tyrannosaurs grow, as well as touches on lingering controversies. Plenty of other blogs have already covered this, so here's a link to the backstory from Brian Switek at Dinosaur Tracking.

Interestingly, the baby Tarb has 15 teeth in the lower jaw, the same number as adult T. bataar. There has been controversy over whether or not tyrannosaurs reduced their number of teeth as they grew, particularly when it comes to the controversial taxon Nanotyrannus lancensis. Nano is known from two specimens (one is nicknamed "Jane") that, depending who you talk to, might really be simply juvenile specimens of the contemporary Tyrannosaurus rex. The differences cited to separate the two boil down to differences in the braincase (certain braincase changes were demonstrated in the new juvenile Tarbosaurus as well), and the number of teeth. Adult T. rex are usually said to have only about 12 teeth in the dentary, while specimens of N. lancensis have a whopping 17. The new juvenile Tarb suggests that in at least some tyrannosaurs, the tooth count is not drastically reduced during growth from juvenile to adult. However, as the authors caution, this same pattern may not necessarily hold true for other tyrannosaurs, even very close relatives.

And, the same pattern does not hold true for the very closely related T. rex. Also making the blog rounds these last few days has been this video of Jack Horner's talk at TEDx in Vancouver (thanks to David Orr at Love in the Time of Chasmosaurs for posting the video link!).



Here Horner gives the basics of his theory that dinosaurs are oversplit, not in the subjective taxonomic sense, but in the more objective biological sense that specimens that could be shown to belong to one species actually represent juveniles of other species. You've all heard the details before, but towards the end he shows a slide (reproduced above) that is pretty damning to the crowd who support the validity of N. lancensis. In fact, adult specimens of T. rex show a very wide ranging tooth count, and it even appears to correspond with relative size (and presumably growth stage. If anything, the number of teeth seen in N. lancensis specimens are only one or two teeth outside the range of variation for T. rex proper, a minor variant that can almost certainly be attributed to ontogeny, and not some cryptic species of giant tyrannosaur lurking in the Lancian faunas that has so far only been identified by two juvenile specimens, while the very common T. rex is known from no juveniles at all.

Anybody know the tooth count for the "Tinker" specimen, currently held in a private collection?

A new study (Carbone, Turvey &Bielby, 2011) suggests T. rex could not have been a pure scavenger.

Yeah, I know. This is already the universally accepted position of modern paleontologists. Of course T. rex scavenged if it could, but there is ample reason to think (and ample fossil support backing this up) that it hunted as well. Even the originator of the scavenging thoery, Jack Horner, has basically admitted that he only came up with it as a way to get young people to think critically about their own preconceptions (obviously, he has never met any young paleontology fans. I'd have given up that strategy after I witnessed my first T. rex vs. Spinosaurus debate).

However, as Denver Fowler pointed out on the DML today, drawing an obvious conclusion is the least of the paper's problems.

I recently participated in at least two paleoart discussion threads in which really awesome artists showed off some mind-blowingly fantastic paintings depicting the Jehol biota. I know first hand that both artists are completely on the ball and know their stuff. But both made common errors in the often neglected field of biostratigraphy.

In one, a Sinornithosaurus watches as two Microraptor glide down from the trees. These are two similar animals from around the same time and place. However, there is no evidence that they ever met. All known fossils of Microraptor come from the Jiufotang formation, dated to 120 million years ago, plus or minus 700k years. The youngest Sinornithosaurus fossils are from the upper Yixian formation, dated to around 122 million years ago. The timespan and environment are grossly similar, but 2 million years is still a long time in a world where most dinosaur species, if not genera, don't span more than a couple million years (and the ones that do are probably egregiously over-lumped, like Iguanodon).

Another painting portrayed a Yixian formation scene with Yixian ornithopods and Yixian insects being fed on by Jeholopterus, a pterosaur which lived in the Daohugou biota, in beds dating to at least 150 million years ago, a full 25 million years before the Yixian faunas existed. The error here was probably based on a confused history of dating the formations (old sources placed the Yixian in the late Jurassic), and many sources, both professional and popular, which tended to conflate the various Chinese feather-preserving formations into one amorphous pseudo-fauna.

Artistic depictions throwing together prehistoric animals from disparate times are obviously nothing new. Walt Disney Pictures has done this at least twice, first and most famously in Fantasia (Stegosaurus meets T. rex meets Pteranodon), and later and more flagrantly in Dinosaur (I can't think of any two animals in that movie that were actually contemporaries, and many didn't even live together on the same continent).

This is somewhat excusable when it's done for the sake of art (as long as that art isn't passed off as being scientifically rigorous). But this kind of disregard for, or generalization of, biostratigraphy can creep into science and completely foul up your results.

In Carbone et al. 2011, the authors attempt to calculate the amount of potential carcasses that would have been available to scavenging Tyrannosaurus rex in its environment to make their case. Their lists of T. rex contemporaries are reproduced in part below:

Species and body masses of carnivorous non-avian theropod dinosaurs of Late Cretaceous North America
Dromaeosaurus albertensis
Richardoestesia gilmorei
Richardoestesia isosceles
Saurornitholestes
Velociraptor sp.
Troodon formosus
Chirostenotes elegans
Chirostenotes pergracilis
Nanotyrannus lancensis
Albertosaurus sarcophagus
Tyrannosaurus rex

Species and body masses of herbivorous dinosaurs of Late Cretaceous North America
Parksosaurus warreni
Prenocephale edmontonensis
Ornithomimus velox
Struthiomimus sp.
Thescelosaurus garbanii
Thescelosaurus neglectus
Leptoceratops gracilis
Montanoceratops sp.
Pachycephalosaurus wyomingensis
Edmontosaurus annectens
Edmontosaurus regalis
Edmontosaurus saskatchewanensis
Lambeosaurus sp.
Parasaurolophus walkeri
Edmontonia rugosidens
Ankylosaurus magniventris
Triceratops horridus
Alamosaurus sanjuanensi

The authors state, "our species list is treated as representing a consistent sympatric faunal unit across this region for the purposes of analysis." But they absolutely don't represent that.

If you have even a little bit of a handle on Late Cretaceous biostratigraphy, or the paleoecology of T. rex, you may notice a few problems with these lists. Namely, the fact that they are complete messes, incorporating erroneous or outdated taxonomic assignments or over-generalizations of the geologic column.

This kind of data crunching would require taxa to be broken down on an environment-by-environment basis. That is, in order to be meaningful, all included taxa have to be demonstrated to be contemporaries. Most of the taxa in those lists were not, or can't be said to have been with any confidence.

To be fair, some of the mistakes are due to very new research, some of which has only appeared in abstracts or mentioned briefly in papers. For example, while Edmontosaurus regalis is widely reported from the late Maastrichtian Hell Creek and Lance formations, this is mainly by default, skeletons that are not identifiable to the species level. Ongoing stratigraphic and taxonomic work by Nicolas Campione has shown that E. regalis was actually not a contemporary of E. annectens, and specimens assignable to that species are only known from lower strata. The validity of E. saskatchewanensis, which is from the same stratographic level as T. rex, is pretty dubious. E. annectens is its likely synonym.

Parasaurolophus is known exclusively from the Campanian-age Dinosaur Park Formation, over five million years before the earliest known T. rex fossils. Same goes for Lambeosaurus. While the former was tentatively identified in the Hell Creek by Sullivan & Williamson (1999), this was based on very fragmentary remains that almost certainly belong to Edmontosaurus instead. Montanaceratops is from the St. Mary River Formation, dated to the early Maastrictian and also pre-dating T. rex.

Some cases are even more nuanced. Alamosaurus did coexist with T. rex, but not with many of the other listed species. Current indications are that the southern part of North America during the late Maastrichtian supported a different fauna from the north, comprised many of species which are related to, but distinct from, their northern counterparts. Alamosaurs, for example, did not coexist with Triceratops, but Ojoceratops (assuming they're distinct). It didn't coexist with Torosaurus latus (which the authors apparently lump with Triceratops), but with "Torosaurus" utahensis. Indications are that these beds are a bit earlier than the late Maastrichtian as well, so while Alamosaurus lived alongside Edmontosaurus, it was E. regalis rather than E. annectens.

The carnivores don't fare much better. Most are tooth taxa, like Troodon (another Dinosaur Park critter from the Campanian). While "Troodon" teeth are known from the same beds as T. rex, they're almost certainly not Troodon formosus. The same goes for Dromaeosaurus. However, these are taxonomic issues, not biostratigraphic ones, and don't really affect species count--whatever we name them, there were at least one troodontid and at least two dromaeosaurids present (though the authors erroneously list both Velociraptor and Saurornitholestes, based on the same specimens, first referred to the former and then the later, both incorreclty). Not so for the inexplicable inclusion of Albertosaurus. I can figure out where these other misplaced species came from, but I don't know of any albertosaur remains having been reported from Lancian-age deposits. Anybody? Either way, it's almost certainly an error (as is making Nanotyrannus a distinct taxon, but that's another story).

So you can see why failing to understand which dinosaurs lived together, specifically, can have major implications for actual science. This kind of paper also illustrates why it's a bad idea to keep non-diagnostic genera around as nomina dubia and not sink them into their better known, probably-synonymous counterparts or simply designate neotypes from the good material. These authors avoided pitfalls like including Thescelosaurus infernalis (=T. sp.), Manospondylus gigas (=Tyrannosaurus rex), Aublysodon molnari (=Tyrannosaurus rex), Thespesius occidentalis (=Edmontosaurus annectens), Trachodon mirabilis (=Edmontosaurus annectens), or Agathaumas sylvestris (=Triceratops horridus), but those taxa aren't doing science any favors by cluttering the playing field.

Here's my preliminary attempt to clean up their faunal lists, based on a Lancian-age, northern ecosystem: (updated thanks to additional information provided by Mickey Mortimer in the comments. note that I'm following the authors in not including avialans)
Dromaeosaurinae sp.
Zapsalis abradens
Richardoestesia gilmorei
Richardoestesia isosceles
Troodontidae indet. spp. (multiple species)