DinoGoss

The Validity of Lambeosaurus - Anybody Know A Good Lawyer?

2013-05-11T17:27:00.000-04:00

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?

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Supporting the Dinosaur/Bird Link in the Era of the MANIAC

2013-04-20T08:44:00.002-04:00

I'm posting this more as an open question than a statement of my own opinion, so comments appreciated!

A new paper out in Paleobiology by Verracchio et al. describes the porosity of Troodon formosus eggs and uses the data as evidence to support the hypothesis that troodontids brooded their eggs, like modern birds and other known maniraptorans, rather than burying them, like crocodilians and some other modern birds. In and of itself, this conclusion is interesting in that it pretty much solidifies nest brooding (as opposed to burial) as the ancestral trait for modern birds, and for maniraptorans (or at least chuniaoans*) in general.

Study coauthor Darla Zelenitsky with Troodon formosus nest. Photo by Jay Im, University of Calgary.

I hate to admit it, but my first thought when reading the headline of this news article from PhysOrg was that, yeah, we all assumed that anyway. The unspoken "rule of cool" is that science tends to be more exciting when we find evidence that contradicts previously well-supported hypotheses, rather than confirming hypotheses we all took for granted. Sure, finding the Higgs-Boson was exciting, but not nearly as exciting as not finding it, which could have led to new physics. I assumed, and I'm sure many others did as well, that troodontids brooded their eggs, based on the reasonably secure hypothesis that oviraptorids (which are known to have done so) are more basal. This behavior in troodontids was even depicted nicely in 2011's Dinosaur Revolution. So score another one for phylogenetic bracketing!

(Of course, this is not to imply that all chuniaoans must have brooded their eggs. It's entirely possible that reversals to burial nesting occurred, as with modern megapodes, and this seems especially likely for very large species like some dromaeosaurines. But the odds that any given chuniaoan would not be a brooder are low.)

Arctic troodontids, anatomy based on Troodon formosus.
Matt Martyniuk, all rights reserved.

Aside from all that, the assertion in the PhysOrg headline struck me as particularly meaningless. How could a study of troodontid brooding lend support to the dinosaur/bird hypothesis? This statement would have been accurate a decade ago, but not today. The reason is the moving goalposts of the dinosaur/bird opposition.

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What's A Monoclonius?

2013-04-10T07:33:00.000-04:00

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

Monoclonius crassus is an iconic ceratopsian, a fixture of many 1970s era dinosaur books, which owes its status almost completely to another species.

I grew up with depictions of Monoclonius in media like Phil Tippet's short film Prehistoric Beast and toys like the DinoRiders figure. Like most representations of Monoclonius in popular culture, these were based on specimens now classified as Centrosaurus apertus (though, actually, that DinoRider looks like it has a genuinely Monoclonius-type frill, long, straight, and unadorned).

Originally known only from teeth and a fragmentary frill and nasal horn, the Monoclonius was one of the first ceratopsians known to science, found by E.D. Cope in 1876 and named for its configuration of tooth roots ("single sprout" as opposed to the "double sprout" of Diclonius, now known to pertain to a hadrosaur).

Like many of Cope's species, Monoclonius was not recognized for what it really was (a "horned dinosaur") until more complete remains from other ceratopsians likeTriceratops were found by Cope's rival O.C. Marsh. Monoclonius itself remaned enigmatic for many years, though the idea of a Triceratops-like ceratopsian with a single large nasal horn was used by Charles R. Knight in his famous painting of Cope's other dubious ceratopsian, Agathaumas. Knight also incorporated spiny dermal armor associated with some supposed Monoclonius remains, though at least some of this material was later shown to belong to ankylosaurs and pachycephalosaurs.

Monoclonius became iconic when complete skeletons of ceratopsians were found in the Judith River/Dinosaur Park Formation of Montana/Alberta. In the early 1900s, C.H. Sternberg (who had co-discovered the orgiinal Monoclonius fossils with Cope) established that complete specimens classified by Lawrence Lambe as Centrosaurus apertus (and some of which were considered to be Monoclonius and which had already been used to form a picture of that animal) were a distinct species. After this, the genus Monoclonius was dismantled, with former specimens re-assigned to either new or recently established centrosaurine genera.

Matters were complicated by the discovery of the drastic changes centrosaurines went through as they grew, and today the distinctive Monoclonius specimens are generally considered juvenile centrosaurines. Zach Miller has done an awesome rendering of a centrosaurine growth series showing where a traditional "Monoclonius" specimen fits into the sequence.

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

However, known specimens of Monoclonius aren't a perfect match for juveniles of the contemporary Einiosaurus, as Miller notes. The long, generally flattened frill with larger incipient spikes at the first three positions of the the parietal (Ryan 2006) are reminiscant of Styracosaurus and Einiosaurus, all of about the same geological age. The large size of a specimen sometimes referred to the distinct species Monoclonius lowei compares with some pachyrhinosaurs like the contemporary Achelousaurus, and while these do begin life with a small nasal horn that later develops into a boss, and though it isn't backward-cureved, such drastic changes during ontogony are known in other ceratopsians. It may be that Monoclonius is a juvenile form of (and therefore a senior synonym of) one of these centrosaurines, or it may be a valid species similar to both, possibly a transitional form between centrosaurin-type centrosaurs and pachyrhinosaurs. Ironically, though long mixed up with that genus, Monoclonius doesn't seem to be as great a match for Centrosaurus itself.

In my restoration of a hypothetical, mature Monoclonius (above), I made it generally styracosaur-like, though with more einiosaur-like parietal spikes, and these could alternately be seen as styracosaur parietal spikes which are not yet fully grown. In this way I've tried to hedge my bets: this Monoclonius could either be a mature, intermediate stage between styracosaurs and einiosaurs, or simply an immature but very large styracosaur.

The nasal horn is restored as styracosaur-like as well, a conservative growth trajectory for the shorter, recurved nose horn seen in subadult specimens of M. crassus and M. lowei. However, it's entirely possible that as the nasal horn grew, it swept forward into the hook-like horn of Einiosaurus or even flattened and thickened into the nasal boss seen in Achelousaurus. Both of those pachyrhinosaurs have long parietal spikes like Monoclonius seems to have had, though both only had a single pair jutting from the back of the frill, while Monoclonius seems to have been developing at least three. Though, again, it's possible the transformation was more extreme than I'm assuming for my illustration, and that these incipient parietal horns were resorbed during growth like the epiparietals of chasmosaurines (e.g. Triceratops).

Rather than the centrosaur-like Monoclonius of my childhood, it looks like this fairly plain-looking ceratopsian grew up into something a bit more spectacular. But we'll need further study and, hopefully, more specimens to find out exactly what, and exactly how extreme, that transformation may have been.

* Ryan, M.J. (2006). "The status of the problematic taxon Monoclonius (Ornithischia: Ceratopsidae) and the recognition of adult-sized dinosaur taxa." Geological Society of America Abstracts with Programs, 38(4): 62.

Clever Girl...

2013-04-06T07:02:00.000-04:00

In honor of the Jurassic Park re-release...

Who Cares About "Dinosaurs"?

2013-03-29T08:10:00.001-04:00

Question: Who cares about dinosaurs?

Short Answer: Marketing departments and monster movie fans.

Above: Not what most people think of when you say "dinosaur."
(Ashdown Maniraptoran by Matt Martyniuk, all rights reserved).

Long Answer:
This is a philosophical issue that's been on my mind for a while now, inspired by some recent and heated debates over the content of the Dinosaur article at Wikipedia. It also seems to be simmering in the background of a lot of discussions about the recent suggestion that Jurassic Park 4 will not feature modern, scientifically accurate dinosaurians.
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No Feathers

2013-03-22T11:32:00.002-04:00

As many of you know by now, Jurassic Park 4 director Colin Trevorrow has (basically) announced via tweet that JP4 would not feature feathered dinosaurs but would stick to the 1980s designs of the original film.

Lots of opinions are flying around paleo blogs and they all raise good points. Andrea Cau has been one of the few to defend the decision by noting that changing the dinosaurs would upset the continuity of the films, such as it is (it's not like we're talking about Lord of the Rings style mythology here). Brian Switek has countered that each previous film has completely re-designed the "raptors" anyway with no in-universe explanation. This has even been jarring in the films themselves. At the beginning of the third film, Sam Neil's character Alan Grant has a dream about a raptor, but it's one of the new raptors (with a totally different skull featuring lachrymal horns, new color scheme, and those bizarre psittacosaur-like quills on the neck), not the raptors he or the audience should remember from JP1.

Anyway, it's obvious the producers don't give a hoot about continuity and are trying to appease the JP fans who love the classic dinosaur designs. That's understandable, but it should also be understandable why a significant portion of the fan base is upset. JP is what got many of us into paleontology in the first place, and the first film went out of its way to emphasize the latest science. Steven Spielberg could have gone with dinosaurs the audience expected in 1993: tripodal, tail-dragging, sluggish reptilian beasts. Instead, he made JP the coming out party for the Dinosaur Renaissance, introducing active, bird-like, Bakkerian dinosaurs to a mass audience for the first time in defiance of expectations (dialogue from the film quickly addresses the inaccuracy of the then-classic dinosaurs as well, like noting that the brachiosaur is warm-blooded and doesn't live in swamps).

So it's a bit sad that JP has eaten its own tail and become the self-perpetuating font of inaccurate science the original film was designed to destroy. The franchise is now a slave to its own cannon and the expectations of its audience, rather than having the guts to challenge those expectations. It will inevitably have to rely more and more on cheap built-in loopholes like frog DNA to briefly explain why the dinosaurs are monstrous relics of a bygone era of science less accurate than the CGI characters on a popular children's show.

As Cau noted in his comments, the only thing that could revitalize the series is a reboot. Here's hoping!

Double Dewlap! What Does It Mean?

2013-01-01T18:08:00.001-05:00

Apatosaurus by Emiliano Troco.

I guess it's an argument for either the collective consciousness, or that there are in fact a limited number of outlandish yet plausible things you can do when restoring sauropod necks, that I came up with a very similar idea many years ago! My execution of the double dewlap sauropod was somewhat... lacking in technical skill compared to Troco's, but you have to admit it is kind of funny that two people independently came up with such a bizarre idea. After a bit of searching I managed to find a really bad scan of my old sketch, presented below or your amusement!

My 2002 drawing of an Isisaurus (Titanosaurus colberti at the time) with double dewlaps. Based on a skeletal by Jaime Headden.

Field Guide Rejects: Arctic Troodont

2012-12-22T08:48:00.001-05:00

Restoration of hypothetical winter & summer plumage in the
unnamed Prince Creek troodontid species, by Matt Martyniuk.

A staple of field guides to modern birds is to illustrate seasonal differences in plumage, which are widespread in cold climates. Of course, we don't currently have any information on plumage variation in Mesozoic birds, but the fact that this is one of the few Mesozoic species that may have regularly encountered snow made it too hard to resist adding this additional layer of speculation.

Field Guide Rejects: Zapsalis

2012-12-17T12:45:00.000-05:00

My new book A Field Guide to Mesozoic Birds and Other Winged Dinosaurs is now available! The book can be purchased via Amazon or CreateSpace. A PDF version is available via Lulu (for those of you reading this via RSS, click through to the Web article for handy links on the right side of the post!).

The problem with writing and illustrating a book covering hundreds of feathered dinosaur species is that it's easy to get on a roll, then get lazy. Specifically, there were one or two instances during the making of the book where I got cocky and finished the bulk of an illustration off the top of my head, only checking it against research later. In all of these instances, I ended up having to modify or flat-out cut the illustration while writing the explanatory text. So much for the info sitting at the top of my head!

Luckily, in many cases I was able to salvage my work by tweaking the paintings in Photoshop to fit a different species, especially where the original was highly speculative to begin with. For example, I was really happy with my initial restoration of the tooth taxon Troodon asiamericanus, and with a few adjustments it now features proudly in the finished book as Linheraptor tani. I was so pleased with my restoration of the possible gigantic velociraptorine (err... itemirine) Itemirus that I chucked out my already-completed restoration of Achillobator (previously featured here), broadened the Itemirus snout, shortened the legs, and used that painting instead. However, there's one restoration I kinda liked a lot that didn't make it into the final book in any form.

Speculative restoration of Zapsalis abradens by Matt Martyniuk

My original plan was to include some of the Lancian-age aviremigian taxa known from very fragmentary remains in the Lance and Hell Creek Formations. I have sitting on my HD right now restorations of Pectinodon bakkeri, the unnamed Scollard formation avimimid, and every named species of Cimolopteryx. I hope one day to complete a field guide style book about the Lance formation, so I probably won't share these just yet (though one of the Cimolopteryx made it into a figure in the finished book along with a few other rejected avians). What I will share is a restoration of a bird I mistakenly thought was a member of this fauna when I painted it. Above is my illustration of Zapsalis abradens, a small (juvenile?) morph of eudromaeosaurs known only from a distinctive kind of tooth (inset). In my mind, I'd always associated this species with the Lance, and Zapsalis-like teeth have been reported from that formation. However, after finishing my painting (which I personally thought came out pretty adorable-looking), I went to do the writeup for it. Tooth taxa do require a bare minimum in the way of research before illustration after all, which is part of the reason why all of them ended up getting cut from the book as too speculative. Lo and behold, the holotype specimen, and indeed most specimens, of Z. abradens aren't from the Lance at all--they're from the Judith River/Dinosaur Park Formation!

So, Zapsalis had two reasons to be cut. One, it was obviously far too speculative to include in a book focusing on comparing externally visible traits. Two, I had to admit that even the name itself is a bit dubious if it's from the DPK. Unlike the Lancian fauna, where no eudromaeosaurs have ever been named and so nothing competes for priority, there are several eudromaesaurs from the DPK. Is Zapsalis a distinct species? Maybe, but if not, it could represent a different morph of either Saurornitholestes or Dromaeosaurus. It would take priority over either name, but without any way to currently tell which (if any) it is, it's kind of a "nomen dubium".

The Field Guide Rejects: Yixianosaurus

2012-12-15T08:26:00.002-05:00

As announced in a few previous posts, Facebook, Twitter, the face of the moon and Geocities probably, my new book A Field Guide to Mesozoic Birds and Other Winged Dinosaurs is now available! The dead tree version can be had through Amazon or CreateSpace and a PDF version is also available for people who prefer to keep their library online/on disk via Lulu (for those of you reading this via RSS, click through to the Web article for handy links on the right side of the post!).

In the interests of continued, shameless self-promotion, I thought I'd do a few blog posts highlighting a bit of the 'making of' the book; in this case, showcasing something that didn't quite make the cut and why.

The first thing I did when switching gears from a guide to the complete ecology of a specific geologic formation to a broad overview of all known Mesozoic birds was decide which species to draw and which to relegate to the appendix. My original criterion, as suggested by John Conway (of All Yesterdays fame) was to include all "reconstructible" aviremigians. I suspect that by "reconstructible" he probably meant "known from a reasonably complete skeleton" but, stickler for completion that I am, I immediately broadened this to mean "anything that could be reasonably drawn based on phylogenetic bracketing." Perhaps understandably, this quickly got out of hand, forcing me to narrow the list down a bit, but not before I'd already painted (I kid you not) Dromaeosauroides and Troodon asiamericanus (the former complete with a tiny inset showing the single known tooth). While I liked the idea of including such never-before illustrated and highly speculative restorations, I thought that the spirit of the book demanded that I include mainly species that would have externally-visible distinguishing features. While there are still a few exceptions included, that is the criteria that produced the final book.

One interesting situation was the few species which did have some externally visible features but are otherwise so phylogenetically ambiguous that most of the reconstruction would be pure fantasy. An example is shown above: Yixianosaurus longimanus. The fact is, despite have a complete forelimb complete with vaned feathers, we don't really have any idea what kind of aviremigian Yixianosaurus is. It's sort of the Deinocheirus of the 21st century. I had restored it basically as I'd imagine a very primitive oviraptorosaur would look, sort of like a cross between Ornitholestes, Falcarius, and Protarchaeopteryx, and it was originally included among the basal caenagnathiformes for lack of a better spot in the book. I'd probably have kept it in if we had complete wing feathers--that would be useful to diagram, at least for artists. But even their length is a guess. So, despite being possibly the most basal known member of the Aviremigia, I had to give this guy the axe.

All Yesterdays: Paleoart Enters A New Era

2012-12-10T06:40:00.000-05:00

For me, one of the biggest biggest paleoart revelations in recent memory was seeing John Conway's digital painting of Diplodocus longus. Its Charles Knight-like "retro" atmosphere, scaly, lizard-like hide, and drooping tail betrayed every piece of received wisdom from the modern paleoart era, which Darren Naish has dubbed the "Age of Paul." Conway himself wrote in the description that the painting represented a "betrayal of the dinosaur renaissance" -- a move away from the sleek, slim, hyperkinetic dinosaurs of Bob Bakker and Gregory S. Paul and back toward a more subdued, naturalistic interpretation of prehistoric life.

In some ways, the pendulum of the dinosaur revolution has swung too far in the hot-blooded direction. Certainly dinosaurs were not the cold-blooded swamp dwellers of the 19th Century, but guess what--many of them probably did live in swamps (including the swampy backwater environments preserved in the Jiufotang Formation) and I bet a lot of them relented to gravity and let their distal tails sag every once in a while; indeed, many of them may even have slept, and I'm not just talking about Mei long! While these statements may seem obvious, such scenarios are rarely portrayed in art.

Sleeping Tyrannosaurus rex by John Conway, from All Yesterdays

In their new book All Yesterdays, Conway, Naish, and C.M. Kosemen usher in a new age of paleoart, and solidify a paradigm shift that makes Paul's classic book Predatory Dinosaurs of the World look as, if not inaccurate, as outdated-seeming as 19th Century dinosaur artwork. The book points out that the anorexic zombie dinosaurs of the Paulian Age are not necessarily the most accurate portrayals of dinosaurs, and that depending on the vagaries of soft tissue preservation and the range of unusual and atypical behaviors found in modern animals, dinosaurs may have looked and acted quite differently from the way they've been shown for the past few decades.

I've long been a proponent of this kind of re-imagining myself. When I first published my recent recon of Archaeopteryx, for example, many of the comments centered on how bird-like it looked relative to most other reconstructions. Really though, I thought it was pretty conservative--all I'd done was give it a reasonable amount of feathering, in an attempt to move it away from the half-bird half-lizard chimeras we usually see. But the stunning artwork presented in All Yesterdays is where the real avant-garde action is, from the tree-climbing protoceratopsids of the cover to the now-infamous, stylized painting of a rutting stegosaur attempting to mount a sauropod!

The final section of the book is even more fascinating and often hilarious. Subtitled "All Todays," it imagines a world in which Quaternary period species are known only from fossils, and future paleoartists try to imagine what they would have looked like in life, mostly from a Paulian-style aesthetic of retaining skeletal outlines wherever possible with minimal soft tissue.

All in all, All Yesterdays is an absolute must-have for anyone interested in the life appearance of dinosaurs and in the cultural context/assumptions inherent in how we reconstruct the past. The book is conveniently available in both eBook and print formats. I personally used the ibooks version for this review, which looks really great, but will definitely be buying a dead tree version in the future, as I think the gorgeous artwork it contains demands a place on my coffee table in all its large-format glory.

All Yesterdays is available in paperback and eBook editions (the Kindle edition seems to come highly recommended on social media, and can be viewed with the Kindle app on iOS and desktop even if you don't have the e-reader).

A Field Guide to Mesozoic Birds: Now Available!

2012-12-08T17:16:00.000-05:00

As you can see by the little ad over to the right of this post, my book on Mesozoic birds is now available in print and eBook/PDF formats! The book should be available in paperback from Amazon US and UK soon, and international distribution will follow soon after. For now, the paperback version can be purchased directly from CreateSpace and the pdf version from Lulu. Additional info and previews can be found here.

As I discussed in my last post about the book, this field guide style summary of our knowledge of Mesozoic winged dinosaurs covers over 150 species and includes appendices on all known species as well as a revised classification and clade definitions.

The Guide has been over two years in the making, so it's definitely nice to finally see it put together in its finished form! I'm pretty happy with the way the paperback came out, and I hope others will be able to get some use out of the anatomical guides and some enjoyment out of the life restorations. My primary goal with this book was to inspire people to see prehistoric birds as more than generic-looking set dressing for larger, more charismatic dinosaurs, and I have to say that it's pretty novel to have all well-known Mesozoic birds portrayed side by side. I hope this effort will help drive home just how diverse and varied in appearance these fascinating animals were!

If you enjoy the book, I hope you'll help spread the word by sharing the links on Facebook, G+, and Twitter, and feel free to let me know what you think by writing reviews!

Coming Soon: A Field Guide to Mesozoic Birds

2012-11-24T07:39:00.000-05:00

The cover, featuring two
squabbling Boluochia

As some of you may have seen when I teased this on Facebook a few weeks ago, I've gone and written a book! With the pithy, concise title of A Field Guide to Mesozoic Birds and Other Winged Dinosaurs, this has been nearly three years in the making, and should be available soon through my website and Amazon.com.

As the name implies, the book is a heavily illustrated "field guide" style summary of known "birds" from the dinosaur era (including deinonychosaurians, caenagnathiformes, and avialans), focusing on most likely life appearances and highlighting what kinds of features may have distinguished each species in life. The book also contains a lengthy introductory section on bird evolution, and on the principles that help in reconstructing life appearance (such as feather arrangement, inferring coloration, distribution of feather types, etc.). Some of this is adapted from research I'd done previously for DinoGoss (such as the section on feather colors), but expanded and updated, and most of it consists of brand new material. The artwork is also pretty much all-new; while some of it had originally been uploaded to my DeviantArt profile (some of you may have seen my entry on caudipterids), most of those pieces ended up being completely re-drawn by the time the book was finished.

The Field Guide covers over 150 species, usually illustrated in multiple views (chosen based on ecology, and with dorsal-view wingspan profiles where appropriate), and each comes with one of my obligatory scale charts. By the time I was finished, I was surprised by how hefty the book turned out. The original conception for the book, as suggested by John Conway, had been to illustrate all "reconstructible" aviremigians--by that, I assume he meant stuff with pretty much complete skeletons. I tried to limit myself to anything with something both distinguishable and visible in life (and pretty much anything with any skull material) despite the urge to produce a few super-speculative pieces (one or two of which made it into the final cut). Anything that couldn't solidly be reconstructed based on skeletal evidence or at least decent phylogenetic bracketing is relegated to an appendix listing all excluded species, but even so, I was a bit surprised that I could manage nearly 150 pretty well-supported illustrations.

Unfortunately (or perhaps fortunately given that it would have taken me another two years to finish), I was just wrapping this book up when two surprising pieces of news surfaced--one, the discovery of pennaceous feathers in ornithomimosaurs, making all of Maniraptoriformes possible aviremigians, and news of a forthcoming study which finds microraptorians, unenlagiines, and troodontids to be avialans and scansoriopterygids to be basal coelurosaurs (potentially making most of coelurosauria aviremigians!). I did manage to include a little discussion of the former in the book, but it will be interesting to read the details of the latter in December. If Scansoriopteryx, which seems to have vaned wing feathers, is actually a fairly basal coelurosaur, a pretty massive supplementary volume may be in order.

Preview of an interior spread featuring Protarchaeopteryx and Caudipteryx.

As I mentioned above, the impetus for this project really came from John Conway, who suggested a guide to all aviremigians based on my field guide style drawings on dA. Unbeknownst to John, I had actually been planning a field guide to the Yixian fauna and flora at the time, but a really comprehensive guide to all Mesozoic "birds" seemed like too good an idea to pass up. John also suggested the idea to self-publish rather than seek traditional publication, which he has been discussing lately on his tumblr.

Due to the vagaries of the publication process, I don't have a definite release date yet, but barring any major hurdles the Guide should be available to order online in paperback before the end of December, so start writing those letters to Santa! Retail price is $36.95 plus shipping from Amazon US or CreateSpace Direct, and it will likely be available at around £25 from Amazon UK and around €36 from Amazon Europe.

The Flying Longipterygids

2012-11-02T09:27:00.002-04:00

I started to get a little carried away in my previous post on longirostrisavisine tails, so I decided to split the finished post in half and use this one to delve a little more into the possible implications the odd tails and clawless wings of that group would have had on their flight styles.

As mentioned previously, longirostravisines, unlike most other enantiornitheans, lacked claws on all three of their manual digits, a trait apparently acquired separately of the Carinatae (Ichthyornis + modern birds). In the last post I speculated that this might have reflected a distinct flying (or at least landing) style. But how much do we really know about longipterygid flight?

Fig. 10 from Close & Rayfield 2012, click to big it up. Note the three general clusters of continuous-flapping (red), soaring and flightless (yellow and gray), and bizarro enantiornithean style (green).

In their recent paper, Close & Rayfield attempted to correlate wishbone (furcula) shape with flight style. Many enantiornitheans in the analysis plotted together in a cluster well separated from modern birds, but close to basal avialans like Confuciusornis which are usually presumed to have been gliders. Oddly, in the Close & Rayfield figure reproduced above, Rapaxavis (no. 103), a longirostravisine, clusters with the weirdo enantiornithean-style fliers, while more basal longipterygid Longipteryx (no. 98) groups with continuous-flapping fliers and is marked as an ornithurine (something seems off here).

In another recent open-access paper on Mesozoic bird flight styles, Wang et. al (2011), using wing element and primary feather length ratios, found Longirostrisavis to be a continuous-flapping flier, and Longipteryx either a continuous-flapping or a flap-gliding flier, roughly the opposite result of the Close & Rayfield furcula-based analysis.

The fact that two independent analyses using two distinct methods produced different results probably does not bode well for the precision of either method. Clearly, we need to figure out better methods to more reliably tests flight styles in extinct birds.

Did Sinosauropteryx Have "Protofeathers"?

2012-08-11T19:51:00.002-04:00

Life restoration of the S. prima type specimen by M. Martyniuk

Over at Jaime Headden's blog The Bite Stuff, Jaime recently wrote a great article about the newly discovered basal coelurosaurian or orionidian Sciurumimus. The article touched on the fact that its feathers were reported as stage 1 (simple, unbranched filaments, often referred to as "protofeathers") in the parlance of feather development researcher Richard Prum. In the comments, Heinrich Mallison pointed out that they *look* like stage 1, but as Foth showed, crushed feathers (even those of modern birds) often look much more primitive than they are due to taphonomic effects. (I've mentioned before in a few places that it's really unfortunate Foth's important paper seems to have been mostly ignored by others writing about fossil feather types). Jaime defended this by saying that Sinosauropteryx, which is more derived, also is 'generally agreed' to have had stage 1 feathers. It's true that this is the general agreement in the literature, and it's also true that the general agreement has been challenged (effectively, in my opinion). I posted a reply to the article, but the fact that this keeps coming up lately has made me think that maybe I should be trying to publicize this more widely, so my comment is reproduced below along with some more commentary on the issue.

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The Strange Bird Dalianraptor cuhe

2012-08-10T18:00:00.000-04:00

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?

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The Tail of Shanweiniao

2012-08-01T18:00:00.000-04:00

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.
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Wrong for the Right Reasons

2012-07-25T18:00:00.000-04:00


Outdated restoration of a Protoceratops andrewsi nesting ground. Painting by Charles R. Knight, 1922.

Flipping through an old dinosaur book from the 1970s or early 1980s can be pretty fun. Nostalgia aside, it's great to see how far the science of paleontology has progressed in just a few decades, and also have a few laughs at the (from our modern perspective) outrageously outdated ideas and reconstructions we find. (David Orr's blog Love in the Time of Chasmosaurs has a great, long-running series covering "vintage dinosaur art" that lovingly pokes fun at some of the mistakes made by past palaeontographers.) Old dinosaur TV shows can be just as good. Last week, Mrs. M recorded a bunch of dinosaur shows for me which were airing on the Science Channel. I hadn't seen any of them before, and didn't realize until I hit play that I was in for a blast from the past. The shows were obviously old-school, narrated by Jeff Goldblum (I assumed these had come out around the time of The Lost World: Jurassic Park until one episode started discussing finds from later in the 1990s like Beipiaosaurus). One episode featured a segment on Roy Chapman Andrew's famous discovery of dinosaur eggs in the Gobi Desert, and the infamous misinterpretation of the eggs as belonging to Protoceratops rather than Oviraptor. This is just the kind of paleontological gaffe we paleo fans get schadenfreude out of today. After discussing the refuted hypothesis that an Oviraptor found on a nest of these eggs was first thought to be eating them rather than guarding them as later finds suggested, Mrs. M asked the obvious question: Why, given that this thing was found on top of the eggs, did they assume the eggs belonged to a different dinosaur?
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The Smallest (Mesozoic) Theropods

2012-06-05T09:40:00.006-04:00

The online community of paleontology fans seems to have an unnatural preoccupation with size. Visit any dino-related message board, and you will find near-daily debates over which carnivorous theropod was bigger (or more specifically, longer). Carcharodontosaurus? Giganotosaurus? Tyrannosaurus? Hint: if the length estimates are within a meter of each other, the weight estimates vary widely, and the beasts in question are known only from one or two fragmentary skeletons, the correct answer is "eh, they're all about the same size, give or take." Also, Therizinosaurus and Deinocheirus, being wimpy herbivores, definitely do not count.

Size comparison of select small non-pygostylian theropods.
From left: Palaeopteryx thompsoni, "Ornithomimus" minutus,
Parvicursor remotus, Epidexipteryx hui.
By Matt Martyniuk, licensed.

Less often, you may come across a discussion about which dinosaur was the smallest. These usually are not the heated debates you find with the mega-carnivores, but rather casual examination of minutiae and bringing up oft-forgotten species. Yes, everybody knows Compsognathus. But did you know the "chicken-sized" type specimen is a subadult or juvenile, and the referred French specimen is much larger? And anyway, Parvicursor was daintier by far. At 34cm (13in) long, Anchiornis was hailed as the smallest dinosaur when it was initially described, but subsequent specimens were larger (up to half a meter in length; still smaller than Compsognathus and slightly shorter than the ~40cm Parvicursor). Epidexipteryx, at a stubby, tail-free 25cm (10in) in length, was the shortest of them all, but its lack of a long tail means that it was a bit larger than the competition in mass. And anyway, isn't Epidexipteryx a bird?

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What Is Enantiornis?

2012-04-01T08:28:00.000-04:00

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.

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The Debate: Newt Gingrich vs. Jack Horner

2012-01-22T08:33:00.000-05:00

This is something I had completely missed until my wife found it linked to on a political blog a few weeks ago. Filmed in 1998, it's a pretty awesome hour-long video of a debate held between paleontologist Jack Horner and then-Speaker of the House Newt Gingrich. The topic: "Were Tyrannosaurus rex active hunters or pure scavengers?" What else?

The debate is actually a follow-up to a previous forum Gingrich did with Horner, both as fundraisers for the Museum of the Rockies. Gingrich, it seems, is an avid armchair paleontologist.

It looks like C-SPAN doesn't let you embed videos, so here's a link to the full debate: http://www.c-spanvideo.org/program/111009-1

What's fascinating about this debate is how it illustrates almost point-by-point a lot of issues I've seen cropping up online lately about the nature of scientific hypotheses, and in particular Horner's approach to them. As some of you may know, Horner recently backpedaled on the whole tyrannosaurs-as-pure-scavengers hypothesis, saying that, from the start, it was merely an attempt to illustrate how the scientific process is supposed to work as opposed to how it often goes in paleo. (Horner explicitly renounced the pure scavenger theory in, among other places, an October 2009 interview on the outstanding Skeptics Guide to the Universe podcast).

Watching this debate unfold, two things surprised me more than I thought they would. First, wow, Gingrich really did his research for this! He comes fully prepared with several examples and analogues to modern ecosystems, many of the same arguments I've seen used in forum debates on this topic, including the fact that there are few if any pure scavengers among modern animals, that hyenas will often take live prey, that vultures can get away with it due to their ability to fly over enormous areas in search of carcasses, etc. Newt knows his stuff, and handily pummels Jack in the debate (though Horner appears to be acting as sort of a gracious host, lobbing him a lot of softballs and overall "letting" Gingrich win.)

The second thing, though, is in Horner's closing arguments. Gingrich easily beats Horner by throwing out analogy after analogy, employing simple logic to demonstrate why his hypothesis "T. rex were not pure scavengers" is superior. But Horner points out, in a way, that it doesn't matter. Debates are antithetical to science. Empirical science is in no way about who has the better argument. It's about who has a more rigorous, testable and ultimately falsifiable hypothesis and can support it with more data, not better analogies.

I have been a T. rex as predators booster since I was 6. But after watching this debate, it is clear to me that Horner has always had a better, more scientific hypothesis and overall approach to the science of paleontology. He is correct that the default assumption has always been that T. rex were active hunters. But at the end of the day, assumptions are not science, and it's a little bit appalling that this assumption has been made an implicit basis of so many statement published in peer-reviewed scientific papers without question. You can never, ever disprove the hypothesis that T. rex were active hunters without a time machine, because it's logically impossible to prove a negative. That's why in science, if we have a positive statement as our hypothesis, it's often necessary to take the null hypothesis (the opposite statement to the one we are testing) and attempt to disprove that in an attempt to support the actual hypothesis. Like string theory, T. rex-as-hunters is an idea that makes logical sense on paper but is unfalsifiable, and therefore not science--just educated speculation.

However, Horner's hypothesis can and has been disproved. We now have evidence of healed-over T. rex bite wounds that show that at least occasionally, they bit living prey species. Does this prove T. rex were active hunters? Not necessarily, but it's a major piece of data against Horner's scavenging hypothesis, and that is actually the strength of Horner's position--that it can be tested and shown to be wrong. In science, it's not always better to be right than it is to be rigorous.

So while he may have won the debate, Gingrich was right for the wrong reasons, while his opponent Horner was wrong for the right reasons.

Bruhathkayosaurus is Dead. Again.

2011-12-21T14:38:00.000-05:00

Above: Working sketches for a speculative B. matleyi reconstruction by Steve O'Connor. Click here for Steve's final drawing.

I don't know how common this knowledge is, but this is the first I've heard of it so humor me while I mourn the possibility of ever re-assessing the intriguingly large sauropod specimen known as Bruthathkayosaurus matleyi.

B. matleyi was known from fragmentary remains of the pelvis and limb bones found in the Tiruchirappalli district of Tamil Nadu, India. It was first described by Yadagiri and Ayyasami in 1989 as species of giant allosauroid. This classification was widely doubted online, but little follow-up work was ever done. The initial description is widely regarded as exceedingly poor in quality and not much can be discerned about the specimen due to poorly detailed drawings and insufficient text. Tom Holtz has even stated that "the hypothesis that this is no more than petrified wood has not been falsified yet to my satisfaction." However, Mickey Mortimer later noted that the tree trunk hypothesis "is questionable given the non-cylindrical bones preserved such as the ilium. Additionally, Chatterjee has personally examined the fossils, and while he has a bad record of misidentifying taxa, I give him enough credit to not confuse a tree for a limb bone."

Sankar Chatterjee did indeed apparently examine the material and told George Olshevsky and Tracy Ford that he believed it to be a titanosaur, as reported in 1999 here.

Holtz responded to these appeals by noting that "not all units are the Dinosaur Park or the Djadokhta. In some preservation is really, really, really crappy. You might get all sorts of authigenic growth on the fossils, or alteration of the original material. In outcrops like that, it isn't out of the question to be fooled into thinking bone is wood and vice versa, especially from simple surficial appearances. This is why a section of the fossil would help resolve if it is bone or wood." So, there's that. We'll now never be able to take that section.

While B. matleyi was a near-mythical celebrity among "semi-apocryphal gigapods", its legend loomed larger than (published) reality. While most online sources (such as the DML posts quoted above) had long since agreed that the specimen was probably a gigantic sauropod and not a gigantic carnosaur, no actual published reference to the species as a sauropod existed until five years ago (Krause et al. 2006).

And what a sauropod it was, maybe! Obviously with such a paltry footprint on the scientific literature, reliable size estimates for such a poorly described specimen are hard to come by. Luckily, some researchers have done the best they could with the available data and determined that, if B. matleyi was indeed a titanosaur with similar proportions to say, Argentinosaurus, it would have been very large indeed. Matt Wedel over at SV-POW has estimated the size of this animal in life at 139 tons. Mickey Mortimer has estimated its length at up to 34 meters. That would position it as one of the largest species of land animals ever, second only to Amphicoelias fragillimus, possibly.

And now, it appears that B. matleyi has suffered the same fate as its atlantosauroid rival for the record. In the comments at another SV-POW post about semi-apocryphal gigapods, Wedel reports that the type and only specimen of B. matleyi was at some point washed away in a flood.
UPDATE: Thanks to Fabrizio in the comments pointing out a source closer to the horse's mouth. Artist "palaeozoologist" at DeviantArt posted an apparent personal correspondance from Kumar Ayyasami last January, in which he reported that the specimen was lost in heavy rains several years ago. (There's some more discussion of the specimen and the author's publication record here, including the suggestion that Dr. Ayyasami may now be deceased--that is, if you can get past the inexplicable Ali G speak). So it sounds like not only was the specimen poorly described, but nobody had bothered to actually collect it from the field site in the ~15 years since its discovery, and it was (predictably and inevitably) lost to erosion.

Any hope of verifying the stupefying claims about this species' size now seem to be lost. And unlike A. fragilimus, which was described and well-illustrated by a mostly reputable source with no obvious errors, the poor state of the B. matleyi description will forever doom this creature to the realm of dubious claims. After all, given the poor state of the description, it seems possible that a simple scale bar error or other mix-up could have tainted the data, and therefore all of our size estimates.

So here's to Bruthathkayosaurus matleyi, a beast (or possibly, a tree?) that died 70 million years ago, raised its spectral head (or crown?) again for one tantalizing moment and then, like Hitchcock's Ornithichnites, sunk back beneath the earth before we could really learn anything about it.

Waddle, _Achillobator_, Waddle!

2011-12-05T10:56:00.001-05:00

"I've hunted most things that can hunt you, but the way these things move..."
"Fast for a biped?"
"Cheetah speed. Fifty, sixty miles an hour if they ever got out into the open, and they're astonishing jumpers."

This quote from the original Jurassic Park film did much to cement the image of dromaeosaurids, the raptor* dinosaurs, in the public consciousness as fleet-footed hyper predators. Despite being nearly 20 years old, this portrayal has by and large remained unchanged in popular culture, with raptors often stock monsters with near-supernatural murderous abilities in everything from tongue-in-cheek xkcd comics to (I hope) tongue-in-cheek made for SyFy movies.

*Yes, I'm going to commit a cardinal sin and refer to dromies as "raptors". "Raptor" in ornithology refers to most predatory birds, even those that hunt on the ground (the Raptor Research Foundation considers Secretarybirds to be raptors). Since dromaeosaurids were both predatory and birds under any sane definition of the word, there should be no problem referring to them as an extinct group of raptors.

But were raptors really particularly fast? Bipedal running speed in digitigrade animals (that is, those that walk on their toes like birds rather than their ankles like humans) is usually roughly determined by the ratio of the lower leg bones (the tibia/tibiotarsus) to the upper foot bones (the metatarsus). The longer the upper foot is in length compared to the lower leg, the faster an animal could run. Therefore, we would expect the fastest theropod dinosaurs to be those with the longest metatarsi relative to tibiae.

A prime example of a theropod specialized for running very very quickly are the parvicursorines. This specialized group of alvarezsaurids (strange theropodan insectivores with stout, powerful arms each bearing one very large claw) has among the longest lower leg to upper leg ratio of any Mesozoic dinosaur group. Looking at the statistics compiled by Mickey Mortimer at The Theropod Database (a phenomenal resource I turn to so often I really should just make it my browser's home page), the type specimen of Parvicursor remotus (see leg diagram here) has a femur 52.6 mm long, a tibiotarsus about 75.6 mm long, and a metatarsus 58 mm long. The functional lower leg is 113 mm long, well over twice the length of the upper leg. More importantly, the lower leg and upper foot bones were fairly close to being equal in length. This animal was clearly a speed demon.

How does this compare to raptors? If, as Jurassic Park claimed, raptors were exceptionally fast, we would expect them to have similarly long lower legs. The terrifyingly human-sized raptors in JP were a Hollywood invention, but we do know of raptor species slightly smaller and slightly larger than they were.

On the smaller side were the famous Deinonychus antirrhopus. According to TTD, the femora of one relatively complete specimen measured 248 mm, with a tibia 324 mm long, and a metatarsus 151 mm long. Again, the total lower leg length is nearly double the upper leg. But the upper foot bones were only half as long as the lower leg bones.

The "fast raptor" meme was started by John Ostrom himself, when he first described Deinonychus in 1969. This was merely speculation on his part, as the hind limb was not completely known in the first specimens. Ostrom actually changed his opinion in later papers, finding that the femur was shorter than he'd initially thought, and that the foot bones were surprisingly short compared to other dinosaurs. Not only was Deinonychus not particularly fast, it probably could not have been nearly as fast as most other small theropods, including modern flightless birds, let alone cheetahs.

Another very popular type of raptors are advanced giant dromaeosaurines (Utahraptor and Achillobator). I recently found myself revising an older drawing of an Achillobator giganticus, which were, as mentioned above, only slightly larger than the Jurassic Park raptors. Many young dinosaur fans are very attached to these species in part because they're much larger than most other raptors, and because they had a slightly anthropomorphized novel written about them by Bob Bakker shortly after JP was released (Raptor Red). As a result, these big birds have a cachet in the collective consciousness similar to the generally more famous Deinonychus and Velociraptor--that of super-fast, agile and intelligent predators.

However, when finishing up my revised drawing, I had to double check the proportions several times to make sure I wasn't screwing it up. To my amazement, the legs, particularly the lower legs and upper foot bones, looked almost laughably short. Again according to TTD, the femur of A. giganticus measures 505 mm long, the tibia 490 mm long, and the metatarsus a paltry 234 mm long--less than half the length of the tibia. Not only is the metatarsus much, much shorter than the tibia, the entire lower leg in only marginally longer than the femur! The first thing that struck me wen looking at my own reconstruction was that this looked like the dromaeosaurid equivalent of Majungasaurus, those abilisaurids with the ludicrously short legs (which, coincidentally like Achillobator, have been suggested to be made up of chimeric specimens). It is also reminiscint of another stout-legged dromaeosaurid species, Balaur bondoc. While Balaur have been suggested to be possibly herbivorous due to these strange proportions, partial jaws and some teeth of Achillobator confirm that they were carnivores. But with legs like those, it's hard to imagine these creatures behaved the way the public imagines raptors to have done, chasing down fast moving prey. Frankly, it's hard to imagine Achillobator doing much beyond waddling across Nemegtian lake shores hunting turtles in epic slow-motion chases.

For the record, no described specimen of Utahraptor preserves both a femur, a tibia, and a metatarsus, so it's impossible to say whether or not they had the same squat proportions (unless somebody has some more detailed information on the numerous undescribed specimens in the BYU collections). For now, it would be safe to assume that they, too, would have been a laughing stock if they were caught trying to run.

Ok, but why would predatory animals have such stubby legs? There is a lot of evidence that dromaeosaurids were specialized for hunting big game, often animals larger than themselves. Deinonychus are infamous for their association with large ornithopods Tenontosaurus tilletti, and while evidence suggests they mainly targeted juveniles (Forster 1984), these were still much larger in terms of weight than even adult Deinonychus. Velociraptor are known to have grappled with the larger Protoceratops, and even a rumored specimen of a Microraptor apparently preserves evidence that they tackled prey larger than themselves. The short legs, especially the short foot bones, seem to be linked with the function of the large sickle-claw, making lack of speed a trade-off for improved ability to grapple and kill large game. Dinosaurs like Tenontosaurus and Protoceratops probably weren't particularly fast-moving themselves, making this sacrifice in speed worthwhile for the chance to down a massive animal that could provide a whole lot of food.

In the end, while the raptor chase scenes in Jurassic Park remain some of the most exciting parts of the movie, they require a significant amount of disbelief to be suspended; after all, it would be more realistic but slightly less suspenseful if Laura Dern had been able to evade the raptors in the power bunker by simply breaking into a light jog.

An Alternate History for "Archaeoraptor"

2011-11-20T17:30:00.000-05:00

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...

Who's That Birdie?

2011-11-19T14:01:00.001-05:00

Because I initially got the inspiration for tomorrow's big post while working on the new restoration above, I thought I'd post it alone first as a teaser. First to correctly guess the species gets a shout-out!