October 22, 2008
What Dinosaurs Walked Here?
Long before the dinosaurs were scientifically described in the early 19th century, their tracks were known. The strange footprints inspired Native American legends and were said to be “turkey tracks” by some European settlers. The first scientific studies of the tracks concluded that they had been made by ancient birds. Single footprints were impressive, but even more astounding were large slabs that recorded that the hoary birds had flocked together. As the science of paleontology developed, however, scientists realized that these tracks were made by dinosaurs, not birds, and people starting finding more tracks all over the world.
One of the most intriguing recent finds, described in the latest issue of the journal PALAIOS, is what has been informally called a “dinosaur dance floor.” It is doubtful that these animals were rocking out to Was (Not Was), but the 190 million year old Jurassic sandstone nestled in the Arizona-Utah border represents a piece of highly trafficked ground, with tracks laid on top of other tracks. Measuring 100 meters long and 30 meters wide, the trackway has about 12 footprints per square meter, and the photographs from the site show a piece of land pockmarked with holes.
Winston Seiler/University of Utah
The majority of the identifiable tracks were made by theropod dinosaurs and carry the names Grallator, Anchisauripus, and Eubrontes. If the names sound unfamiliar, it is because footprints are named differently than skeletons are. Unless a dinosaur dies in its tracks and it preserved, it can’t be certain what genus of dinosaur which made each type of track, so tracks are identified based upon tell-tale characteristics and given their own names. Prints left by a sauropod-relative (a sauropodomorph) were also found at the site.
Of particular interest was a tail-drag mark. During most of the 20th century dinosaurs were depicted as animals that dragged their tails on the ground behind them, but the majority of evidence (from skeletons to trackways) showed that dinosaurs held their tails off the ground. The tail-drag mark does not overturn what has been learned about dinosaur posture, but it does indicate that a dinosaur that walked on four feet and had a long, sinuous tail briefly dragged it on the ground.
Why did so many dinosaurs congregate in this one area? The high amount of tracks is certainly unusual, but the answer may have to do with a shortage of water. Around the track site were huge sand dunes that were part of an immense desert, but the tracks themselves were made on a damp surface near an ancient water source. This site may represent a prehistoric watering hole in which many different kinds of dinosaur came to drink (and perhaps some even preyed on the animals that came to quench their thirst).
There is a lot more work to be done at the site, particularly because the paleontologists found a new kind of track they had never seen before. Could this site preserve traces of a dinosaur otherwise unknown to scientists?
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Why, oh why did you mention Was (Not Was)? I have not had that horrid song stuck in my head for like, 15 years now.
Where’s some industrial-techno…I have to purify…
(A synchronicity — I haven’t thought of Was(Not Was) in years but just a couple of days ago I was walking to school and the demon DJ in my brain [I suffer badly from Dysphoric Melodic Mnemonic Syndrome -- my kill or cure prescription is the brutally catchy instrumental Popcorn] spat out, “Man versus man/man versus nature/man versus the Empire Brain Building.” I suppose it’s just a matter of time before I’m getting down with Fun Boy Three and the Burning Sensations.)
I’m legally obligated to mention that the cool thing about tracks is that they’re fossilized behavior — they’re the only solid evidence of behavior we have.
Speaking of behavior, you do know that it’s very cruel to mention a new type of track without giving us any details. How does it differ from other tracks? Any guesses as to what it may be? What types of dinosaurs don’t have tracks associated with them? Inquiring minds wish to know!
After reading about the Acambaro dinosaur figurines some years ago, I finally got a chance to go to Mexico to the Julsrud museum to see and handle parts of the collection firsthand. Throughout most of the twentieth century, dinosaurs were thought to be sluggish, dragging their tails. The Chupicuaro culture or an earlier culture accurately depicted dinosaurs in the newer revised manner, but the figurines have been dated to be about 3000 years old or more.
The earlier scientific depiction rested on the assumption that gravity and the size of the animals required a sluggish depiction. I’m surprised that current theory hasn’t pointed at the splitting of the continents as a cause for mass extinctions. They admit the occasional catastrophe, but not enough so as to cause them to utterly throw out uniformitarianism completely. USGS charts have proven there is no sea floor older than the Jurassic and that both the Pacific and Atlantic seafloors are the same age.
Good point about tracks being fossilized behaviour, Sean. I hadn’t thought about them that way before.
Hmm.
Is anybody else annoyed by the way most news outlets carried this story, as a “dinosaur dance party”? I mean, have we reached the point where dinosaurs are no longer interesting enough to warrant their own stories unless they are also dancing?? Many thanks to Brian for allowing this story to stand, or walk – but not dance – on its own merits!
Thanks for the compliment, Hugh, although I think the “dancing dinosaur” imagery came from one of the authors of the paper! In one of the reports I saw (although I can’t remember where), Chan said that all the holes in the ground reminded her of Dance Dance Revolution pads, and she referred to it as a dinosaur dance floor. (I ran with it a little with the Was (Not Was) reference, but that was too good to resist).
What I found most interesting, though, was that the dinosaurs were probably walking over and between immense sand dunes in something akin to today’s Sahara, congregating at watering holes. It made me think of footage I’ve seen from Africa, particularly what happens when watering holes shrink and dry up. Imagining such a scene with dinosaurs is exciting, and the new tracks provide some clues about how they survived in a harsh environment.
[...] on creative press releases, and provides a helpful round-up of informative articles (including a posting by our own Brian Switek) on the recent discovery of prehistoric tracks densely packed on a 3/4-acre [...]