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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.

The Thermopolis specimen of Archaeopteryx at the Wyoming Dinosaur Center. Photo by the author.

Since the time the English anatomist Richard Owen described Archaeopteryx as the “by-fossil-remains-oldest-known feathered Vertebrate” in 1863, the curious creature has been widely regarded as the earliest known bird. Lately, though, the status of the iconic animal has been up for debate. Earlier this summer, one team of paleontologists proposed that Archaeopteryx was not a bird but actually a feather-covered, non-avian dinosaur more closely related to genera like Microraptor and Troodon. Now a different team of paleontologists has published a paper in Biology Letters that says Archaeopteryx was an early bird after all.

The ongoing back and forth over Archaeopteryx reminds me of the old Looney Tunes bit where Bugs Bunny and Daffy Duck keep going back and forth over which hunting season it is. “Duck season.” “Wabbit season!” “Duck season” “WABBIT SEASON!” In the same way, the argument over Archaeopteryx could seemingly go on indefinitely. The reasons why have everything to do with how both science and evolution work.

The study of prehistoric life, like any other science, is not restricted to the slow and steady accumulation of facts. Facts are most certainly acquired through studies in the field and lab alike, but to tell us anything significant about dinosaurs, these facts must be understood according to theories and hypotheses. An exasperated Charles Darwin conveyed this truth eloquently in an 1861 letter he wrote to colleague Henry Fawcett:

About thirty years ago there was much talk that geologists ought only to observe and not theorise; and I well remember some one saying that at this rate a man might as well go into a gravel-pit and count the pebbles and describe the colours. How odd it is that anyone should not see that all observation must be for or against some view of it is to be of any service!

Facts, theories and hypotheses are all necessary and interacting parts of the scientific process. As new discoveries are made and ideas are tested, the context by which we understand what dinosaurs were and how they lived changes. This is to be expected—there are always more questions and mysteries about dinosaurs than readily available answers. In the case of Archaeopteryx, we know this feather-covered dinosaur lived on a group of roughly 150-million-year-old islands that would eventually become southeastern Germany. Whether or not Archaeopteryx belonged to that successful lineage of feathered dinosaurs called birds, though, is something that depends on other feathered dinosaur discoveries and the techniques used to test ideas about relationships among animals.

Teasing out relationships among prehistoric animals is a comparative science. The key is finding traits that are shared in some organisms due to common ancestry but are absent in others. This can be a tricky process. Due to a shared way of life, for example, unrelated organisms may have developed superficially similar traits through a phenomenon called convergent evolution. Paleontologists must carefully choose the traits being compared, and the discovery of additional dinosaurs adds more grist to the comparative mill.

Archaeopteryx is actually a perfect example of how new discoveries can change our perception of relationships. When the first skeleton was discovered in 1861, nothing quite like it had been found. Archaeopteryx seemed to stand by itself as the first bird. Over a century later, though, the discovery of dinosaurs such as Deinonychus, an updated understanding of dinosaurs and the eventual discovery of many, many feathered dinosaurs illustrated that Archaeopteryx exhibited a number of transitional features that illustrated how the first birds evolved directly from feathered dinosaurs.

The trouble is that Archaeopteryx appears to be so close to the emergence of the very first birds. At the moment, Archaeopteryx is most often regarded as being an archaic member of the group called the Avialae, which contains all birds (Aves) and forms more closely related to them than to other dinosaurs. What this means is that, as our understanding of what a bird actually is changes, the position of Archaeopteryx might shift. The animal might have been one of the earliest birds within the avialian group, or Archaeopteryx might have been just outside the bird group among non-avian dinosaurs.  This is simply how science works and is a wonderful—if frustrating—demonstration of the fact of evolution.

Birds did not simply pop out of nowhere. The earliest avians went through a long period of transformation, and the continuum between feathered, non-avian dinosaurs and the first birds, which paleontologists are now filling in, demonstrates the beauty of major evolutionary change. The debate over the position of Archaeopteryx is happening now precisely because of all the evidence for this evolutionary change that has been accumulated in the past two decades. No matter what Archaeopteryx turns out to be, the creature will remain important to both the historical development of our ideas about evolution and the actual, prehistoric transition from non-avian to avian dinosaurs.

For more on changing perspectives on long-known dinosaurs, see this week’s post on the fate of the horned dinosaur Torosaurus.

References:

Lee, M., & Worthy, T. (2011). Likelihood reinstates Archaeopteryx as a primitive bird Biology Letters DOI: 10.1098/rsbl.2011.0884

Xu, X.; You, H.; Du, K.; Han, F. (2011). An Archaeopteryx-like theropod from China and the origin of Avialae Nature, 475, 465-470 DOI: 10.1038/nature10288

The 11th skeleton of Archaeopteryx. Photo by Helmut Tischlinger.

For Archaeopteryx, 2011 has been a year of ups and downs. Paleontologists celebrated the 150th anniversary of when the iconic feathered dinosaur was named. But shortly afterwards, a controversial paper in Nature in July proposed that the creature—widely hailed as the first bird—was further removed from avian ancestry than previously thought. Now Archaeopteryx is back on the upswing. According to a press release circulated by the New Munich Trade Fair Centre in Germany, paleontologists now have an 11th specimen of the famous fossil creature to study.

Until this week, ten Archaeopteryx skeletons were known to paleontologists, not including the fossil feather the German paleontologist Hermann von Meyer used to give the animal its name. Peter Wellnhofer, the world’s foremost expert on the “urvogel,” detailed the backstory of each fossil in his comprehensive book Archaeopteryx: The Icon of Evolution. The London specimen and the Berlin specimen are the best known—particularly the latter, arguably one of the most visually stunning fossils ever found—but there’s also the busted-up Maxberg specimen, another that was initially confused for a pterosaur (the Haarlem specimen) and a slab known as the Solnhofen specimen that was originally thought to contain the skeleton of the small coelurosaurian dinosaur Compsognathus.

As far as I am aware, the new specimen does not have a name and has yet to be described in the literature, but this Archaeopteryx appears to be one of the more complete and well preserved of the lot. In fact, the preservation and position of the bones are reminiscent of the Thermopolis specimen I saw in Wyoming this past year, although this new Archaeopteryx is missing one forelimb and the skull. Don’t be fooled by the fact that, at first glance, the fossil looks a little jumbled up. If you start by following the tip of the tail (on the right), the articulated vertebral column leads to the hips and splayed legs before curving up and back in the classic dinosaur death pose. The arm is displaced below the hips but remains articulated.

We will have to wait for the descriptive paper to learn the important characteristics of this new find, as well as where the slab came from. But if you happen to be in the vicinity of the New Munich Trade Fair Centre in Germany, you can see the 11th Archaeopteryx for a limited engagement at “The Munich Show” from October 28-30.

Other fossilized beasts might be more intimidating than Archaeopteryx, but few others have played such an important role in our understanding of evolution. Courtesy of Brian Wolly.

A dispatch from Smithsonian.com’s associate web editor Brian Wolly:

Earlier this month, I took an extended vacation overseas ostensibly for a friend’s wedding but also to explore continental Europe. The wedding date conveniently allowed me to be in Munich for the start of Oktoberfest, an overwhelming experience in and of itself that’s better left for another Smithsonian blog. But when I read in my guidebook that Munich had a paleontology museum, and a free one at that, I couldn’t pass up the chance to contribute to Dinosaur Tracking. Since Bavaria’s very own Archaeopteryx was named 150 years ago today, on September 30, 1861, here’s my account of the small but charming Paläontologisches Museum München.

Located on the campus of Ludwig Maximillian University, the museum has a quaint, meditative quality that outstrips its otherwise aged appearance. When I visited, high school art students were sketching the fossils of their choosing; had they not been there, I’d have been mostly on my own. All the captions were in German, understandably, so I was left with just my imagination to decipher the stories behind these dinosaurs and other fossils. Considering that most of what I know about dinosaurs I learned from Brian, I had a great time comparing notes from three years of producing the blog to the objects in front me. For instance, on the second floor was the museum’s shrine to Archaeopteryx, including a couple of model reconstructions and the Munich specimen, a subject that we’ve covered heavily in this space. The 150-million-year-old Archaeopteryx historically has been considered the direct ancestor of birds, a designation that is recently under dispute.

On a rainy Sunday afternoon, the museum was the perfect antidote for my Oktoberfest-addled brain. For more photos, check out the gallery and let us know in the comments what other great paleontology museums you’ve discovered on your vacations.

View our gallery of photos from the Munich Paleontology Museum.

The skeleton of Xiaotingia (head is to the left). From Xu et al., 2011.

Sometimes my timing is just plain awful. I had waited for years to see an authentic specimen of Archaeopteryx—the feather-covered fossil celebrated for 150 years as the first bird—but by time I finally got my chance, on the afternoon of July 27, news sources were trying to out-pun each other over the unceremonious demotion of the evolutionary icon. I scanned through the reports while sitting in the parking lot of the Wyoming Dinosaur Center, where the only Archaeopteryx in North American is on display. “Archaeopteryx Knocked From Roost as Original Bird” claimed WIRED Science, and the BBC played up the drama with “Feathers Fly in First Bird Debate.”

All this hubbub was stirred up by an article published a few hours before I rolled up to the museum in Thermopolis, Wyoming. In the issue of Nature published that day, paleontologist Xu Xing and colleagues described a previously unknown species of feathered dinosaur from the exceptionally fossil-rich beds of Liaoning, China. An interesting find, but given the number of feathered dinosaurs discovered during the past 15 years, not exactly something that newspapers would flip over. (As a freelance science writer, believe me that convincing some editors that dinosaurs are worth talking about is an uphill struggle.) What made all the difference was the way the new fossil was used to challenge the traditional position Archaeopteryx has held.

The backstory for the news goes back to 2009. In that year Xu and other paleontologists described a feather-covered creature they called Anchiornis. At first they thought it was an early bird, but a follow-up paper identified it as a feathered troodontid dinosaur. The newly described creature was very similar to Archaeopteryx—so much so that the discovery made me wonder if the beloved “urvogel” might eventually be stripped of that title, especially since Anchiornis might be even more ancient than the 150-million-year-old Archaeopteryx.

Now there’s Xiaotingia zhengi—another small theropod dinosaur draped in well-developed plumage. The holotype specimen which formed the basis of the new Nature paper exhibits the mostly complete skeleton on its side, and altogether the specimen looks like a tan and brown smudge of bones and feather impressions. It is said to date back to about 155 million years ago, but like many such fossils from China, the exact date is frustratingly uncertain because the fossil was purchased from a dealer and not scientifically excavated. In terms of the anatomical nitty-gritty, though, Xiaotingia looks quite similar to both Archaeopteryx and Anchiornis. Even though the skull was crushed, for example, Xiaotingia appears to have had a short skull fitted with small, peg-like teeth.

But the part of the study that garnered the most attention was the evolutionary analysis which removed Archaeopteryx and its closest kin from the base of the bird family tree. According to the paper, the dinosaurs Archaeopteryx, Anchiornis and Xiaotingia were united by several subtle characteristics, such as the lengths of the hand bones and the shape of the wishbone. The study places these dinosaurs closer to the sickle-clawed deinonychosaurs—the group which contains genera like Troodon and Deinonychus—than to the earliest birds.

Now here’s the part that was grossly underreported. “It should be noted,” the authors of the new paper wrote, “that our phylogenetic hypothesis is only weakly supported by the available data.” Headlines proclaimed the downfall of Archaeopteryx even though the actual evidence for such a change, as the authors of the study admitted, is not particularly strong. The uncertainty stems from the fact that some of the features seen in early birds may have appeared independently in more distantly related dinosaurs, so determining which traits are true signs of family ties and which evolved independently in different lineages is a difficult task. For example, the authors of the new study point out the similarity between the skulls of early birds such as Jeholornis and Sapeornis with oviraptorsaurs—all seem to have relatively deep and short skull profiles. But is this a real sign of close relationships, or a case of convergent evolution? There is no definite answer yet. When trying to tease out relationships, paleontologists must choose wisely or else features that evolved independently might be mistaken for common inheritance from a shared ancestor.

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