Saturday, December 22, 2012

Field Guide Rejects: Arctic Troodont

My new book A Field Guide to Mesozoic Birds and Other Winged Dinosaurs is now available! The book can be purchased via Amazon or CreateSpaceA 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!).

Happy winter! Here's one more entry in my series of Field Guide illustrations too speculative to include in the book. It's now pretty widely known that remains attributed to the Campanian age genus Troodon have been found in the Maastrichtian age Prince Creek Formation of northern Alaska, which would have been above the arctic circle at the time. These animals have been featured in some recent TV documentaries such as March of the Dinosaurs. Though the remains are fragmentary and mostly undescribed, the fact that they are later in age than Troodon formosus, and in some cases twice the size of comparable T. formosus remains, it's a near certainty in my and others' opinions that these represent a new species if not genus of troodontid.
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.

Monday, December 17, 2012

Field Guide Rejects: Zapsalis

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".

Saturday, December 15, 2012

The Field Guide Rejects: Yixianosaurus

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.

Monday, December 10, 2012

All Yesterdays: Paleoart Enters A New Era

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).

Saturday, December 8, 2012

A Field Guide to Mesozoic Birds: Now Available!

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!

Saturday, November 24, 2012

Coming Soon: A Field Guide to Mesozoic Birds

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

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.

Friday, November 2, 2012

The Flying Longipterygids

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.

Saturday, August 11, 2012

Did Sinosauropteryx Have "Protofeathers"?

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.

Friday, August 10, 2012

The Strange Bird Dalianraptor cuhe

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?

Wednesday, August 1, 2012

The Tail of Shanweiniao

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.

Wednesday, July 25, 2012

Wrong for the Right Reasons

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?

Tuesday, June 5, 2012

The Smallest (Mesozoic) Theropods

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?

Sunday, April 1, 2012

What Is Enantiornis?

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.

Sunday, January 22, 2012

The Debate: Newt Gingrich vs. Jack Horner

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:

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.