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Another year, another fantastic spate of dinosaur discoveries. Even as 2011 draws to a close, the findings keep rolling in—from the way Deinonychus used its killer cutlery to the first record of sauropod dinosaurs from Antarctica and sexual selection among dinosaurs. There has been such a glut of interesting papers that it would be impossible to mention every bit of dinosauriana from this year, but here is a partial listing of some of the stories that caught my eye.

Dinosaur Growth

Everyone knows that there are lots of unknown dinosaur species left to be discovered. What has become increasingly contentious is the question of how many species can be counted among what has already been collected. This year saw a continuation of the 2010 “Toroceratops” debate with a paper on the enigmatic Nedoceratops by Andrew Farke early in the year, followed by a response to his paper by John Scannella and Jack Horner this month. Likewise, paleontologists suggested that the hadrosaur Anatotitan and the tyrannosaur Raptorex were really just growth stages of other known dinosaurs (the latter being similar to Tarbosaurus, a juvenile of which was also described this year).

Dinosaur senses

How did dinosaurs perceive their world? Two significant papers approached this question—one focused on smell (see the video above), and the other vision. As with studies of dinosaur growth, though, investigations of dinosaur senses can be controversial. Last week’s issue of Science included a comment and reply about the idea that the bony rings preserved in the eyes of some dinosaurs might be used to reconstruct the time of day when the animals were most active.

Archaeopteryx

This year marked the 150th anniversary of the discovery of Archaeopteryx. But 2011 has been full of ups and downs for the Urvogel. Even though an 11th specimen of the feathered dinosaur was announced, a controversial paper proposed that the creature was not an early bird but rather a non-avian dinosaur more distantly related to the first birds. Exactly what Archaeopteryx is and what that interpretation means for our understanding of bird evolution will continue to be debated.

New species

New dinosaurs are named just about every week, but two in particular caught my eye: Brontomerus, a sauropod whose name translates to “thunder thighs,” and Teratophoneus, a short-snouted tyrannosaur. (I just realized that both were found in Utah, though, so perhaps I have a bias for my adoptive state!)

That is just a smattering of findings from 2011. Shout out your favorite 2011 dinosaur discoveries in the comments. And, if you want to see how 2011 compares to previous years, see my lists from 2010 and 2009.

Since Jack Horner and James Gorman’s book How to Build a Dinosaur debuted almost three years ago, periodic lectures, interviews and articles have piqued the public’s curiosity about reverse-engineering a non-avian dinosaur from an avian one. Perhaps a “chickenosaurus” isn’t as outlandish as it sounds.

The possibility of creating a long-tailed chicken with teeth and claws is based on the fact that birds are living dinosaurs. A relatively minimal amount of tinkering could turn a bird into something like its non-avian ancestors. But, during the dinomania of the late 1980s and early 1990s, the idea that birds were derived from dinosaurs was still something that made people tilt their heads and say “What?” Rather than focus on efforts to turn birds into something akin to a dromaeosaur, dinosaur documentaries envisioned the real evolutionary changes by which one lineage of non-avian dinosaurs were adapted into early birds. Even better, two shows animated this change.

Within the array of Mesozoic programming from the early 1990s, one of my favorite shows was The Dinosaurs! This four-part PBS miniseries featured scientists investigating the details of dinosaur lives, and different prehistoric vignettes were presented in colorful animated sequences. The one that stuck with me most powerfully was a short scene about the origin of birds. A small, green dinosaur akin to Compsognathus runs through a forest, but when the theropod pauses on a branch it rapidly grows feathers. In an instant the small coelurosaur changed into Archaeopteryx. The 19th century naturalist Thomas Henry Huxley was absolutely right when he imagined that, when clothed in feathers, a dinosaur like Compsognathus would look little different from archaic birds.

But a similar clip from an earlier, 1989 episode of the series The Infinite Voyage is even better. The episode, “The Great Dinosaur Hunt,” is an excellent snapshot of how perspectives on dinosaurs were changing in the wake of the “Dinosaur Renaissance,” and the program included a similar coelurosaur-to-bird transformation. This time, though, the change starts with a fuzzy, feather-covered dromaeosaurid similar to the sickle-clawed Deinonychus. Rather than focus on the outside of the dinosaur, though, the show gives viewers an animated X-ray view as the skull, arms, shoulders, legs and hips are gradually modified in a transition through Archaeopteryx and modern birds. The change didn’t happen exactly like this—Deinonychus was a larger dinosaur that lived millions of years after Archaeopteryx—but different anatomies represent the general pattern of the evolutionary change.

I still have a fondness for those animations. Part of that affinity is probably due to nostalgia, but I also think that they beautifully illustrate a point that is often taken for granted now. The fact that birds are modern dinosaurs is reiterated in books, museum displays, CGI-ridden documentaries and blogs, but rarely do we see the transitional changes actually laid out in front of us. Both animations could use some updates, but they still vibrantly encapsulate one of the most fantastic transitions in the history of life on earth.

An articulated Iguanodon hand on display at London's Natural History Museum. Photo from Flickr user Meffi.

There is much we still don’t know about dinosaurs. In fact, some aspects of dinosaurs have puzzled paleontologists for well over a century. Among the most frustrating is why the great herbivore Iguanodon had prominent thumb spikes. Despite all the possibly explanations provided for this appendage, none are especially satisfying.

The peculiar false thumb of Iguanodon was originally thought to set into the dinosaur’s nose. When Gideon Mantell first described the animal in 1825, the various bits and pieces of the dinosaur were thought to represent the remains of an enormous, iguana-like reptile. As a result, it seemed reasonable that a conical, bony spike corresponded to the same structure on the snouts of rhinoceros iguanas. This placement made sense within the prevailing view that creatures like Iguanodon were lizards writ large, but the idea was tossed when a series of more complete Iguanodon were found in a Belgian coal mine in 1878. The “horn” actually belonged on a mitten-like hand, opposite a prehensile finger.

But why should Iguanodon have a hand spike? The most popular idea is that the dinosaur used the appendage for defense—an illustration by John Sibbick in The Book of Dinosaurs shows and Iguanodon stabbing its spike into the neck of an attacking allosaurid. The restoration looks more than a little ridiculous. In order to get within poking range, the defending Iguanodon would have to place itself right in front of its assailant, perfectly within the range of the slicing dental cutlery of the carnivore. Such maneuvers would require the attacker to hold still while being prodded. One popular-audience book suggested that the spike might house a venom gland, but there is no evidence for this and, furthermore, the Iguanodon would still have to get within biting range of the attacking theropod to use the weapon.

There are a few other speculative hypotheses. Maybe Iguanodon used the spikes in combat with one another. Or perhaps, as David Norman briefly suggested in his section on basal iguanodontia in the second edition of The Dinosauria, the spike was used for “breaking into seeds and fruits.” These are not unreasonable notions, but there is also no positive evidence to suggest that they are correct, either. The Iguanodon thumb spike is a strange specialization that must have originated for a reason. The question is whether we can test any of these ideas.

Though my own suggestion is not any better than those I have been disappointed by, I wonder if the Iguanodon spike is a Mesozoic equivalent of another false thumb seen among animals today—the enlarged wrist bones of red and giant pandas. Perhaps the Iguanodon thumb spike was an adaptation for stripping foliage from tree branches. The dinosaur could have grasped the branch with the prehensile finger, or flexed the main fingers of the palm around a bough, and run the spike down the branch to remove the greens without having to chew through the less-nutritious twigs. But this hypothesis has problems, too. The false thumbs of pandas flex so that they help the mammals grip bamboo, whereas the Iguanodon spike was rigid. And why would an Iguanodon preferentially select greener browse, especially when supplied with a formidable battery or self-replacing teeth? Furthermore, this idea is difficult to test—a preserved thumb spike wouldn’t show wear from use the same way a fossil tooth would. The Iguanodon spike was surrounded by a tough, keratinous sheath, so the actual wear wouldn’t be seen on the bone itself. A functional model of an Iguanodon hand could help investigate this idea, but even then, direct evidence would be lacking.

Perhaps there isn’t a good modern analog for the Iguanodon spikes. The bones look like they could be used for any number of things, from defense to feeding, but frustratingly, there isn’t any unambiguous indication of what they were used for or why they evolved. Perhaps, to solve this mystery, we need to go beyond the obvious and try to think like a dinosaur.

When it came time to pick a 2011 Christmas tree ornament, the choice was clear - I needed a dinosaur. Photo by the author.

When it came time for my wife and me to pick this year’s Christmas ornament, there was no question what it had to be: We needed a dinosaur. After all, this year we left New Jersey to settle in the fossil-rich state of Utah, and so it was only appropriate to celebrate our successful move with a dinosaurian decoration. We settled on an Allosaurus pendant from Dinosaur National Monument. This Late Jurassic theropod—one of my favorite dinosaurs—is the official state fossil of my new home, and my first visit to the geologically wonderful national park two years ago was what inspired me to head west. Perfect.

But my wife and I aren’t the only ones to adorn our tree with dinosaurs. Friends have been sending me snapshots of their own tannenbaum dinosaurs over the past few weeks, and yesterday I put out a call for more merry Mesozoic ornaments. I was not disappointed.

Photo by Michael Barton.

Long-time reader Michael Barton tweeted this Cretaceous scene wherein a Triceratops faces off against a Tyrannosaurus. C’mon, guys—don’t you know that this is the time of year for peace on earth and goodwill towards dinosaurs?

Photo by John Pomeranz.

Among other dinosaurs, John Pomeranz nestled this particularly colorful Triceratops among the branches of his Christmas tree. With no predators around, this dinosaur clearly doesn’t need camouflage.

Photo by Aline McKenzie.

Even though pterosaurs aren’t dinosaurs, I couldn’t say no to this photo of one of the flying archosaurs decked out in a Santa hat, sent by Aline McKenzie.

Photo by Helen Fields.

What’s flashier than a Stegosaurus? A sequin-covered Stegosaurus ornament, of course. Thanks to freelancer Helen Fields—who has written about dinosaurs for Smithsonian herself—for this one.

Photo by Matthew Cobb.

Those sparkly stegosaurs sure do get around. This one, tweeted by Matthew Cobb, had been shuffling around the Christmas tree since 1986.

Photo by Twitter user @scurvygirl.

A vintage theropod reaches out from @scurvygirl’s Christmas tree.

Photo by Twitter user @ArtfulMagpie.

Given their probable diet of conifers, I’m surprised there aren’t more holiday sauropods in the mix.  Fortunately for us, though, @ArtfulMagpie has shared this lovely pink sauropod from her Christmas tree. She says “He was a brontosaurus when I got him as a child. I suppose he’s an apatosaurus now!”

Photo by Alexandra Witze.

A cute little Triceratops lives in Alexandra Witze’s Christmas tree, but where there’s Triceratops…

Photo by Alexandra Witze.

…Tyrannosaurus is not far behind. Though, based upon the lipstick, I’d say this one is ready to make love, not war.

Photo by Marc Vincent.

Of course, the fellows at Love in the Time of Chasmosaurs have unique dinosaur decorations, too. These two dinosaurs, sent by Marc Vincent, are out for a nice winter sleigh ride…

Photo by David Orr.

… and LITC founder David Orr has this fuzzy Spinosaurus, crafted by his wife.

Photo by Flickr user cali4niadreamn23.

Even museums have jumped in. This tree—inhabited by many origami dinosaurs—is on display at the American Museum of Natural History in New York. I think this tree wins the category of “most dinosaurs per square inch.” Thanks to fellow science writer Alexandra Witze for the tip about this one.

Do you have holiday dinosaurs in your home? Don’t hesitate to send them to us at dinosaursightings@gmail.com. We will create an end-of-the-year roundup for whatever other dinosaurs might appear. Until then, all of us here at Dinosaur Tracking want you to wish you warm and happy holidays, wherever you are.

An early 19th century representation of Megalosaurus at the Crystal Palace gardens. Thomas Henry Huxley's work gave dinosaurs a much more bird-like look. Image by Flickr user Loz Flowers.

Winter is the season for dinosaur dinners. Both Thanksgiving and Christmas traditionally feature avian dinosaurs as the main gustatory event, and according to paleontological legend, it was this custom that inspired one 19th century naturalist to realize the connection between roasted birds and Jurassic dinosaurs.

Mark Norell, Lowell Dingus and Eugene Gaffney recounted the story in their book Discovering Dinosaurs. “One Christmas Day,” they wrote, “[Thomas Henry] Huxley was carving a turkey for his annual feast. As he dissected the drumstick he was struck by an unmistakable similarity between his Christmas dinner and the fossils of the theropod Megalosaurus back in his office.” From that day on, the story goes, Huxley was convinced that there was a deep genetic connection between dinosaurs and birds. I heard to same story from my Paleontology 101 professor at Rutgers University. It is a charming bit of lore. And it’s also wrong.

I don’t know where the story about Huxley and the Christmas turkey came from. It is one of those stories that seems simply to exist in the academic ether. (Even the Discovering Dinosaurs authors voiced their uncertainty about the tale in their book.) Fortunately for us, though, Huxley’s many scientific papers trace the development of his thoughts about birds and dinosaurs.

Huxley began associating reptiles—including dinosaurs—with birds on the basis of their anatomy in the early 1860s. Both groups appeared to be different variations of a common skeletal blueprint. But Huxley wasn’t thinking about this in evolutionary terms yet. He was primarily interested in the commonalities of structure and did not immediately start drawing evolutionary implications from the anatomical correspondences he recorded. That changed in 1866, when Huxley read the German naturalist Ernst Haeckel’s book Generelle Morphologie, an influential volume that connected organisms in a tangled “tree of life.” In regard to birds and reptiles, at least, Huxley realized that he had already established the basic outline of an evolutionary transition from a dinosaur-like creature—something resembling Compsognathus—to flightless birds and culminating in flying birds.

Huxley did not suggest that birds were the direct descendants of dinosaurs. So much geologic time was unaccounted for, and so few dinosaurs were known, that Huxley could not point to any known fossil creature as the forerunner of birds. Instead he made his argument on anatomical grounds and removed the issue of time. Dinosaurs were proxies for what the actual bird ancestor would have been like, and flightless birds (such as the ostrich and emu) stood in for what Huxley thought was the most archaic bird type. (We now know that Huxley got this backwards—the earliest birds could fly, and flightless birds represent a secondary loss of that ability.) As Huxley went about collecting evidence for his case, though, he also gave dinosaurs an overhaul. They were not the bloated, plodding, rhinoceros-like creatures that Richard Owen had envisioned. Dinosaurs were more bird-like than anyone had imagined.

In October of 1867, Huxley met with John Philips, an English geologist and a curator of Oxford’s museum. As Huxley related in his 1870 paper “Further Evidence of the Affinity Between the Dinosaurian Reptiles and Birds,” Philips wanted to discuss details of marine reptiles called ichthyosaurs in his museum’s collection, but as he and Huxley made their way over toward the displays they stopped to look at the bones of the carnivorous dinosaur Megalosaurus. Then Huxley spotted something peculiar:

As Prof. Phillips directed my attention to one after the other of the precious relics, my eye was suddenly caught by what I had never before seen, namely, the complete pectoral arch of the great reptile, consisting of a scapula and a coracoid ankylosed together. Here was a tangle at once unravelled. The coracoid was totally different from the bone described by Cuvier, and by all subsequent anatomists, under that name. What then was the latter bone? Clearly, if it did not belong to the shoulder-girdle it must form a part of the pelvis; and, in the pelvis, the ilium at once suggested itself as the only possible homologue. Comparison with skeletons of reptiles and of birds, close at hand, showed it to be not only an ilium, but an ilium which, though peculiar in its form and proportions, was eminently ornithic in its chief peculiarities.

Earlier naturalists had made a mistake. They had misidentified the shoulder girdle, and one part of what was thought to be part of the shoulder was actually part of the hip. Another strange piece, previously thought to be a clavicle, also turned out to belong to the pelvis. This rearrangement immediately gave the dinosaur a more bird-like character. It wasn’t only the small, gracile forms such as Compsognathus that shared skeletal features with birds. Philips himself had been pondering the bird-like characteristics of Megalosaurus even before Huxley arrived, and Huxley’s visit confirmed what Philips had previously suspected. The resulting, updated conception of Megalosaurus was closer to the animal as we know it today—a theropod dinosaur with a short forelimbs, long legs, a long tail for balance and a deep head filled with sharp, recurved teeth.

Huxley’s Christmas revelation is apocryphal. Rather than being instantly struck by the idea that birds and dinosaurs were closely related, Huxley carefully built up an argument over many years that birds evolved from something dinosaur-like. As far as I know, his only sudden realization regarding Megalosaurus involved the rearrangement of bones in Philips’ care at Oxford. And I think this brings up a crucial point often missed or glossed over in accounts of Huxley’s work. Through his efforts to untangle bird origins, Huxley was pivotal in revising the image of dinosaurs into active, bird-like animals. New fossil finds, as well as a new anatomical framework, changed dinosaurs from ugly beasts into graceful, unique creatures during the 1870s, thanks at least in part to Huxley’s efforts. (Too bad that succeeding generations of paleontologists would unravel this vision by casting dinosaurs as dumb, cold-blooded reptiles.) Even if Huxley didn’t say birds are dinosaurs, he certainly made dinosaurs more bird-like.

For more information on Huxley’s thoughts on dinosaurs and birds, please see my paper “Thomas Henry Huxley and the Reptile to Bird Transition” and chapter 5 of my book Written in Stone.

References:

Huxley, T.H. 1870. Further Evidence of the Affinity Between the Dinosaurian Reptiles and Birds. The Quarterly Journal of the Geological Society of London, vol. xxvi. 12-31

Norell, M., Dingus, L., Gaffney, E. 2000. Discovering Dinosaurs: Expanded and Updated. Berkeley: University of California Press. p. 11