October 19, 2011
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.
September 30, 2011
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.
August 26, 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.
April 12, 2011
Hunting dinosaurs is a dangerous business. Scores of fictional, time-traveling hunters have learned this lesson the hard way, but arguably the most unfortunate was the protagonist of Brian Aldiss’ short story “Poor Little Warrior.” All Claude Ford wanted to do was get away from his disappointing life and unhappy marriage by gunning down prehistoric monsters. Slaughtering a swamp-dwelling Brontosaurus briefly satisfied his escapist desires, but, unfortunately for Ford, the dinosaur had been home to scores of lobster-sized parasites that scurried off their dead host and onto the closest, warmest living thing.
Paleontologists have not yet found such monstrous Mesozoic parasites, but familiar pests did afflict dinosaurs. Tiny trematode and nematode worms lived in the guts of predatory dinosaurs, and Tyrannosaurus itself was plagued by a harmful microorganism commonly found among modern pigeons. But not all dinosaur parasites were internal. Although not as terrible as Aldiss’ creatures, prehistoric lice may have made the lives of many dinosaurs very itchy.
The prehistory of lice is poorly understood. Out of five supposed fossil lice scrutinized by entomologist Robert Dalgleish and colleagues in 2006, only one, a 44-million-year-old specimen described by Dalgleish, Torsten Wappler and Vincent Smith two years earlier, turned out to be the genuine article. Curiously, though, the single fossil specimen appeared to be a close relative to feather lice found on modern birds, and the researchers who described it suggest that birds may have “inherited [lice] from early-feathered theropod dinosaurs.”
(A 100-million-year-old relative of lice was announced in 2006, but it was a “booklouse” that was not an animal parasite.)
As yet, no feathered dinosaur specimen has been found with preserved lice, but a Biology Letters study just published by Smith and a different team of collaborators suggests that the pests might have taken up residence on some Cretaceous species. This hypothesis is based on comparisons of modern louse lineages. Since the prehistoric feather louse and the older “booklouse” remain the only finds close to the early history of lice, the scientists behind the new research used the genetics of living louse species to estimate when their respective lineages would have diverged from one another.
What the scientists came up with was a hypothetical tree of louse evolution. The genetic divergence estimates suggest that parasitic lice were diversifying just after 100 million years ago in a Late Cretaceous world teeming with hosts. Exactly which hosts these insects parasitized is unknown.
Even though news reports about the new study have focused on the likelihood that at least some dinosaurs were bothered by lice, the aim of the research was to use a fresh line of evidence to ascertain the timing of when lineages of modern birds and mammals began to appear. This is a subject of some dispute among scientists. Many paleontologists place the major radiation of modern bird and mammal groups after the end-Cretaceous mass extinction about 65 million years ago, but scientists using genetic and molecular techniques have suggested that these lineages originated deeper in the Cretaceous. Since lice are relatively host-specific and are associated with particular groups of birds and mammals, Smith and co-authors used the evolutionary pattern of lice to draw bird and mammal lineages back into the heyday of the dinosaurs. The lice appeared to track what was believed to be the early origins of modern groups.
But the tight connection between extant louse families and lineages of modern mammals and birds is an assumption. If the new study is correct, parasitic lice proliferated during the Late Cretaceous, when there were already plenty small mammals and feathered dinosaurs running around.
Smith and co-authors state that Archaeopteryx was the oldest-known feathered dinosaur at approximately 150 million years old, but Anchiornis may have pre-dated its more famous cousin by 10 million years or so. Either way, feathers and feather-like body coverings had already been present for over 50 million years before parasitic lice evolved. Smith and colleagues also cite the oldest known fossil hair as dating to about 55 million years ago, but paleontologists have found the exquisitely preserved bodies of much older mammals with intact fur, the approximately 125-million-year-old Eomaia being just one example. As with feathered dinosaurs, furry mammals were around for a long time before the first lice, and studies of fossil mammal evolution have also confirmed that there were many now-extinct groups of mammals present during the Late Cretaceous. Perhaps parasitic lice got their start on feathered dinosaurs and archaic mammals and were only inherited by lineages with living descendants later on.
Smith may have summed up the significance of the new findings best in a quote he gave to the New York Times: “The louse phylogeny adds one more piece of data to this puzzle. It says lice are old, predate the Cretaceous-Paleogene boundary, and must have been living on something.” What those “somethings” were remains unclear. Evolutionary estimates based on genetics make predictions about what may yet be found, and it will be up to paleontologists to test these hypotheses with the remains of long-dead creatures.
DALGLEISH, R., PALMA, R., PRICE, R., & SMITH, V. (2006). Fossil lice (Insecta: Phthiraptera) reconsidered Systematic Entomology, 31 (4), 648-651 DOI: 10.1111/j.1365-3113.2006.00342.x
Smith, V., Ford, T., Johnson, K., Johnson, P., Yoshizawa, K., & Light, J. (2011). Multiple lineages of lice pass through the K-Pg boundary Biology Letters DOI: 10.1098/rsbl.2011.0105
Wappler, T., Smith, V., & Dalgleish, R. (2004). Scratching an ancient itch: an Eocene bird louse fossil Proceedings of the Royal Society B: Biological Sciences, 271 (Suppl_5) DOI: 10.1098/rsbl.2003.0158
February 16, 2011
Over the past fifteen years, paleontologists have described more than twenty species of feathered dinosaurs. Even dinosaurs once thought to have dry, scaly skin, such as Velociraptor, have turned out to have feathers. But paleontologists have actually known of at least one feathered dinosaur since the mid-19th century. They just did not know to call it a dinosaur.
In 1861, the German paleontologist Hermann von Meyer described two remarkable fossils preserved in slabs of 150-million-year-old limestone. The first was a single feather—a sure sign that birds have been around for quite a long time—but the second was not as easy to interpret. A partial skeleton surrounded by feathers, the creature seemed to be almost equal parts reptile and bird. Since the skeleton had come from the same type of limestone quarry as the feather, though, von Meyer concluded that both fossils represented the same animal, and he applied the name he had given the feather to the skeleton. Together, these were the first recognized remains of Archaeopteryx lithographica.*
Archaeopteryx immediately became one of the most famous fossil creatures ever discovered. The trouble was that no one could agree on what it was or its relevance to the evolution of other animals. Richard Owen, who purchased the skeleton for what is now London’s Natural History Museum, thought that Archaeopteryx was the earliest known bird, whereas his rival Thomas Henry Huxley thought that it was an evolutionary dead end that did not tell naturalists much about how birds actually evolved. Even though many naturalists recognized that Archaeopteryx was important to questions about how birds evolved from reptiles, there was very little agreement about how that change occurred.
It has only been in the past few decades, with the confirmation that birds are just modified dinosaurs, that Archaeopteryx has been placed in its proper evolutionary context. Although now pre-dated by the feathered dinosaur Anchiornis, Archaeopteryx remains one of the oldest feathered dinosaurs known and is still central to questions about bird origins. (Whether it is actually the earliest bird, though, depends on how we define what a bird is, something that has become increasingly difficult as paleontologists have found more dinosaurs with bird-like characteristics.) The several specimens of Archaeopteryx now known are some of the most exquisite and most important fossils ever found, and so it is fitting that this feathered dinosaur gets a little extra attention for its big 150.
Over at Pick & Scalpel, paleontologist Larry Witmer reports that Germany will be issuing a special 10-Euro commemorative coin imprinted with the famous Berlin specimen of Archaeopteryx (which was discovered in 1877). These will be available on August 11th of this year, just a few days before the 150th anniversary of the first written mention of the fossil. Germany’s Humbolt Museum will also be opening a new exhibit called “Feathered flight—150 years of Archaeopteryx.” For now, that is all that is formally planned to celebrate Archaeopteryx, but Witmer promises that he’ll be adding photos to a Facebook Archaeopteryx gallery throughout the year, and I plan on writing a few posts about this famous fossil as we approach the big August anniversary.
*I say “first recognized” because an Archaeopteryx specimen was discovered in 1855 and misidentified as a small pterosaur by von Meyer in 1875. Its true identity was not discovered until John Ostrom reexamined it in 1970.