October 7, 2011
Hadrosaurs just can’t get any respect. In a new paper published in PLoS One, paleontologists Nicolás Campione and David Evans have proposed that the immense, Late Cretaceous hadrosaur Anatotitan was actually just the fully mature stage of the dinosaur Edmontosaurus. No one batted an eyelid: “Huh? Anato-what?” Compare the lack of reaction to the tizzy the public fell into last year when confused reporters mistakenly told readers that paleontologists were sinking the name Triceratops. As far as I know, no one has started up a “Save Anatotitan!” group to object to the conclusions of Campione and Evans.
The new hadrosaur paper is just the latest in a growing body of research on the changes Late Cretaceous dinosaurs underwent as they grew up. In 2009 Horner and co-author Mark Goodwin proposed that the dinosaurs Dracorex and Stygimoloch were juvenile and sub-adult stages of the dome-headed genus Pachycephalosaurus, and Horner and John Scannella proposed that the horned dinosaurs Nedoceratops and Torosaurus were more mature growth stages of Triceratops. (Regarding each case, the names Pachycephalosaurus and Triceratops would be preserved while the others would be sunk.) These papers have been very controversial among paleontologists. Have we really been naming too many dinosaurs, or are we now entering an age when we’re lumping too many together?
So far, the focus of the lumping/splitting debate has been on the Late Cretaceous dinosaurs of western North America. The work by Campione and Evans continues this trend with Edmontosaurus and closely related genera. Specifically, the paleontologists chose to investigate 23 edmontosaur skulls, ranging from Edmontosaurus regalis and Thespesius edmontoni from roughly 73-million-year-old deposits in Alberta, to the dinosaurs Edmontosaurus saskatchewanensis, Edmontosaurus annectens and Anatotitan copei from the time interval spanning roughly 70 to 65 million years ago. Just how many of these dinosaur genera and species are valid has been debated for some time, and the new research narrows down this list to just two species of Edmontosaurus.
Through comparisons of particular anatomical landmarks on each edmontosaur skull, Campione and Evans concluded that individual variation and anatomical changes due to growth had led other researchers to name too many hadrosaurs from the pocket of Late Cretaceous deposits they investigated. Hadrosaurs given the name Thespesius edmontoni simply appear to be small individuals of Edmontosaurus regalis from the same deposits, while Edmontosaurus saskatchewanensis and Anatotitan copei seem to be younger and older growth stages, respectively, of Edmontosaurus annectens. Just like that, five different dinosaurs are reduced to two species of a single genus.
Further study and debate will test the hypothesis proposed by Campione and Evans. (For example, do changes in bone microstructure follow the proposed growth series for Edmontosaurus annectens?) Of one thing, though, there can be no doubt: just how many different dinosaurs existed in North America during the last ten million years of the Cretaceous has become a matter of major debate among paleontologists. How things shake out will undoubtedly influence our understanding of how and why dinosaurs became extinct on the continent. If some of the new studies are correct and the number of different dinosaurs in western North America at the end of the Cretaceous was lower then previously expected, then we are left with the question of why the drop in diversity occurred and whether the changes made dinosaurs more vulnerable to extinction. Then again, if genera like Torosaurus, Dracorex and Anatotitan are preserved, we must ask how so many similar dinosaurs evolved and co-existed alongside each other. Right now, it is too early to tell. We are only at the beginning of what may become an important and long-running debate about how dinosaurs grew up and why they disappeared.
Campione, N., & Evans, D. (2011). Cranial Growth and Variation in Edmontosaurs (Dinosauria: Hadrosauridae): Implications for Latest Cretaceous Megaherbivore Diversity in North America PLoS ONE, 6 (9) DOI: 10.1371/journal.pone.0025186
May 2, 2011
The Discovery Channel’s “March of the Dinosaurs” is the kind of dinosaur documentary that could not have been made until this point in time. When I was first becoming acquainted with dinosaurs in the mid-1980s, the thought of dinosaurs braving the cold temperatures and long nights of Arctic winters seemed absurd. Dinosaurs dwelt in warm, lush environments – not within the reaches of the Arctic Circle.
But we now know dinosaurs truly did live that far north. Hard-won fossil discoveries have turned up traces of Late Cretaceous Arctic habitats that, while a bit warmer than they are today, are still unlike the typical setting we imagine dinosaurs in. Drawing on these finds, “March of the Dinosaurs” offers some imaginative reconstructions of snowbound dinosaurs.
Narrated by Stephen Fry, the docudrama carries on in the tradition of shows like “Walking With Dinosaurs” in telling stories about individual animals rather than explaining the science behind the reconstructions. Scar – a young Edmontosaurus who narrowly escaped a hungry tyrannosaur – and a fluffy Troodon named Patch are the stars of this new program. While Scar travels south with the hadrosaur herds, Patch stays put and tries to make a living in the snowy Arctic forest.
The dinosaurs themselves look pretty good. Their creators adorned the Troodon and tyrannosaurs with feathers, and they were well-detailed for TV-special creatures. The dinosaurs were a bit drab – they were almost uniformly gray, with a few splashes of orange here and there – and there were a few anatomical mistakes, but the dinosaurs still looked better than some of the CGI monstrosities that have stomped across cable channels in the past few years.
Frustratingly, there are plenty of silly story elements that mar the program. Although the tyrannosaurs Gorgosaurus and Albertosaurus are the story’s principal villains, for example, they are not very good at hunting. They miss juvenile hadrosaurs that are standing still, repeatedly roar to announce their presence, and – in one shot that made me laugh out loud – pursue prey by doing aerobatic ninja leaps that would have been impossible for the living animals. The documentary also tells us that Albertosaurus – unlike Gorgosaurus – hunted in packs, but, since the actual science behind the dinosaurs is not included in the story, we are left to take the Stephen Fry’s word for it. The same goes for the show’s assertion that Troodon could see in slow-motion, and that their mating season began at the height of winter. After the first twenty minutes, especially, speculation replaces science as the basis for the show.
Paleontologist Dave Hone had similar feelings about the documentary. “[I]t [would] be nice to have just a few token words towards the science a little more often, not least on something billed as a ‘documentary’”, he wrote. I agree. Arctic dinosaurs are so unfamiliar that I feel the show could have benefited from the inclusion of more science – perhaps interspersing dramatizations with scientists explaining how they know what they know about these habitats. Not only would this have provided viewers with a little more context, but it might have resulted in a better overall show. Towards the end, Scar and Patch have faced so many over-the-top perils that what are meant to be dramatic sequences of live-and-death struggle feel rather flat. (And dinosaur comic fans will no doubt see some pretty obvious similarities to Ricardo Delgado’s story Age of Reptiles: The Journey.)
Not every dinosaur documentary needs to include talking heads or focus on the search for dinosaurs in the field. There is a place for strong narratives about the lives of dinosaurs. Like many other dinosaur documentaries, though, “March of the Dinosaurs” takes a unique premise and tries to stretch it a bit too far. Explanations of how scientists reconstruct prehistoric environments can enrich stories if sewn into the narrative the right way, and, in this case, I think the show’s creators missed an important opportunity to do so. Watch “March of the Dinosaurs” for the feather-covered Arctic dinosaurs, but, if you want to know more about them and their world, you will have to turn to other programs like NOVA’s “Arctic Dinosaurs.”
August 27, 2010
Every year scores of paleontologists head out to the field in search of dinosaur fossils, but sometimes the remains of the charismatic creatures are hiding right underfoot. As reported in various news outlets earlier this week, sewer construction workers Aaron Krywiak and Ryley Paul discovered dinosaur bones while working 120 feet under the city of Edmonton in Alberta, Canada. The fossils were from at least two well-known dinosaurs that lived about 75 million years ago, near the end of the Cretaceous: the tyrannosaur Albertosaurus and the hadrosaur Edmontosaurus. Teeth, vertebrae, and ribs are among the bones discovered by the duo, and city workers are going to cooperate with paleontologists from the Royal Tyrrell Museum and the University of Alberta to make sure future discoveries in the tunnel are carefully collected while diminishing construction delays.
July 8, 2009
In the winter of 2007, news agencies were all a-twitter over the news of another “mummy” hadrosaur found in North Dakota. Nicknamed “Dakota”, the dinosaur was said to “exceed the jackpot” of what paleontologists could have hoped for, and two books, a documentary and a lecture tour were arranged to promote the fossil. All the while, however, scientists have been waiting for a scientific description of Dakota to be published. After a long wait, the first detailed study of Dakota finally appeared in the Proceedings of the Royal Society B this past week.
Dinosaur mummies, or dinosaurs with skin impressions intact, have been known for over a century. What might make Dakota special, however, is that the fossil preserves much more than just the impressions of the skin. As recent research by paleobiologists like Mary Schweitzer has shown, sometimes degraded remnants of original dinosaur organic material can survive the fossilization process under the right conditions. The authors of the description of Dakota suggest that their specimen, too, contains some detailed traces of the dinosaur’s original body.
Even though the body of “Dakota” has yet to be fully uncovered, and the paleontologists are still unsure as to what species of Edmontosaurus the dinosaur is, enough of the fossil has been studied to reveal the exceptional detail of the dinosaur’s preservation. Indeed, it appears that the fossil preserves about two inches of skin, not just impressions of the top layer, and in the skin layer are what appear to be cell-like structures. There even seemed to be remnants of the tough sheath that would have covered some of the toe bones (“dinosaur toenail”), and tests suggested that it, too, was preserved material from the original dinosaur’s body.
These findings are not quite as dramatic as the studies of preserved Tyrannosaurus and Brachylophosaurus soft-tissue structures carried out by Mary Schweitzer and her colleagues, but it does suggest that we should look more closely at some other known “dinosaur mummies.” Perhaps they too preserve some cells or other minute details that have been ignored. Paleontologists will continue to search for and study bones, but a whole new branch of paleontology is opening up inside the microbiology lab.
March 16, 2009
|New Orleans Audubon Zoo Exhibit
Exhibitions of robotic dinosaurs seem to be back on the upswing. They were very popular when I was growing up but have been harder to find in recent years. According to reports released over the weekend, however, zoos in Cleveland and New Orleans will be featuring the jerking, growling robot dinosaurs this summer.
This past weekend, the New Orleans Audubon Zoo opened their “Dinosaur Adventure” exhibit. It features 16 dinosaurs such as the old favorites Tyrannosaurus and Triceratops as well as some newer robots like Giganotosaurus. Hard-core paleo fans will still be able to complain that the theropods are holding their hands wrong and that the raptors are not covered in feathers, though.
The Cleveland Metroparks Zoo will open a similar exhibit in May featuring many of the same animatronic dinosaurs. (The dinosaurs for both zoos are being supplied by Billings Productions.) I think the Metroparks Zoo press office might have overhyped one of their dino stars a little bit, though. One section of the press release for the exhibit reads;
Along the beautiful shores of Waterfowl Lake, DINOSAURS! 2009 features species of beasts never before displayed at the Zoo—including the Edmontosaurus, with its thousands of razor-sharp teeth…
Edmontosaurus did have a mouth packed with sharp little teeth, but they were used for eating plants. Indeed, this dinosaur was a hadrosaur. Given that I have only ever heard the phrase “razor sharp” in referring to the teeth of carnivores, though, I got the distinct mental image of a bloodthirsty Edmontosaurus chasing after smaller dinosaurs in the attempt to get a snack.