(Field work has temporarily ceased for the past two days because of intermittent rain, occasional high winds, and powerful waves that are causing seawater to cover up the beautiful Cretaceous along the coast here in Victoria. In the meantime, here is the first part of a two-part series on burrowing dinosaurs.)
Why am I here in Victoria, Australia, when perfectly fine and extensive outcrops of Cretaceous rocks are in the western U.S.? Heck, Cretaceous rocks are even in southern Georgia. From Atlanta, I could drive just a few hours to see those, instead of flying to Los Angeles and dealing with the hellish nightmare of LAX, just before squeezing myself in between two fellow anonymous travelers for the 15-hour flight to Melbourne, then recovering from jet lag for a few days after that, which is only cured by alternating consumption of fine Australian coffee drinks with beers. (OK, so the last part isn’t so bad.)
There are several reasons why I traveled more than halfway around the world to see the rocks here, versus just staying put in Georgia. One is that most of the Cretaceous rocks in Georgia are covered by an invasive creeping vine called kudzu, which is so bad, it inspires the geologists there to consider bringing back the much maligned (but probably just misunderstood) defoliant Agent Orange. Most Cretaceous rocks in southern Georgia are also weathered to the point where people living there just call it “dirt.”
Kudzu (Pueraria montana), covering the landscape, trees, houses, and slow-moving children in Georgia, and the bane of geologists there and elsewhere in the southeastern U.S., giving good reason to fly for more than 24 hours to see a decent amount of Cretaceous rock containing some tasty trace fossils.
Most importantly, though, the Cretaceous rocks in Georgia were formed in shallow-marine environments. Now, I personally hold no animosity against marine environments (not even mild scorn), and in fact have done several studies of trace fossils made by critters that formerly lived in shallow- and deep-marine environments. But if you want to study how dinosaurs, mammals, insects, and their companions really lived during the Cretaceous – and I do – then you’d best look at rocks formed by freshwater river sediments.
Sure enough, sediments of former rivers, lakes, and other inland environments were responsible for making the Cretaceous rocks here in Victoria. When we stand on these rocks, we sometimes share the same spot where a dinosaur stood, a mammal scurried, or an insect conducted insect business, which mostly consisted of feeding itself or making more insects. But still, it’s pretty neat to know that these rocks are the remnants of environments shared by those and other animals.
A very happy me, taking notes on many geological and paleontological observations of Cretaceous rocks in Victoria, Australia, which is all made possible by their not being covered by kudzu.
So that’s a few reasons for being here. The one of the most important reasons is that this is one of only two places in the world where dinosaur burrows were interpreted. And I was connected to both of those interpretations.
“What’s that?”, you say. “Dinosaur BURROWS?” Just in case you've never heard of such a thing, and you somehow imagine a tyrannosaur emerging from a hole the width of the Holland Tunnel, don't feel bad. This is still a new concept in dinosaur paleontology. The first firm evidence for burrowing dinosaurs wasn’t found until 2005. The second place was about, as the lorikeet flies, in Cretaceous rocks about 20 kilometers (12 miles) from where I’m sitting right now. This place is called Knowledge Creek: more about it soon.
Although no scientific clues for burrowing dinosaurs existed before 2005, Tom Rich and Patricia (Pat) Vickers-Rich proposed burrowing as a behavioral strategy for Victorian dinosaurs in a paper in 1988. So why did they make such a silly statement, with seemingly no data to back it up? Well, if you recall from a previous post or two of mine, the environments here were near the South Pole 105-120 million years ago, and it got chilly, especially during the winters. Tom and Pat further reasoned that the small dinosaurs living in this area could not have migrated – that required too much energy – so the simplest way for them to survive a polar winter would have been to stay in burrows. Lots of modern critters do this in polar environments, including polar bears, so why not dinosaurs?
Were there any burrowing dinosaurs? Yes. The first known burrowing dinosaur from the geologic record was discovered in Cretaceous rocks of western Montana in 2005, although it was not revealed to the scientific community until 2007. This dinosaur was named Oryctodromeus cubicularis, which literally means, “digging runner of the lair.” It was a small ornithopod dinosaur that lived about 95 million years old, and it had several anatomical traits showing it was well adapted for burrowing.
Profile view based on preserved bones and a close-up portrait of the “digging dinosaur,” Oryctodromeus cubicularis, from 95 million years ago in what we now call Montana, yet another place that lacks kudzu and has great exposures of Cretaceous rocks. Illustrations by Lee Hall.
Very luckily, this dinosaur was also found in a fossil burrow of the right size, and was entombed with two of its partially grown offspring. Remember, in science we like to have multiple lines of evidence to support our hypotheses, so to have both trace fossil and body fossil evidence, especially with multiple specimens, and all in the same place, was very nice indeed.
Artistic rendering of an adult Oryctodromeus cubicularis and its OH THEY’RE SO DARNED CUTE offspring (soon to be dead and fossilized) in a den made by the adult dinosaur. Artwork by very skilled paleoartist Mark Hallet, done for a special issue of National Geographic, May 2008.
The second piece of evidence for burrowing dinosaurs was “just” from trace fossils, and no bones were involved. During my first visit to Victoria in May 2006, I noticed a couple of odd structures in an outcrop of the Otway Group (from about 105 million years ago) at a foreboding place Knowledge Creek. (Yes, even its name is laden with symbolism, evoking thoughts of the River Styx – not to be confused with the ‘80s band Styx, of course.) This was less than a year after Oryctodromeus had been discovered, although this dinosaur had not yet been announced to the world. One of the Knowledge Creek structures, though, almost perfectly matched the size and shape of the burrow associated with Oryctodromeus.
Wait a minute: how did I know that then, in 2006? Oryctodromeus and its burrow were still unknown to the scientific community, and the paper describing it would not be published until early 2007. Was I clairvoyant, really good at guessing random ideas, or (most likely of all) spiritually inspired by The Flying Spaghetti Monster?
The short answer is, none of the above: I had inside knowledge. At the time, I was part of the research team working on Oryctodromeus, and had seen and studied its burrow only eight months beforehand, which looked almost exactly like the Knowledge Creek burrow. It was a coincidence that, much like Glenn Close’s character in Fatal Attraction, would not be ignored. (All right, I must admit that I didn’t then pursue the dinosaur burrows in a murderously vengeful way after having an affair with them. So perhaps it was more like Pee Wee’s Big Adventure.)
To make a long story short, one of the big reasons why I am here is to look for more evidence of burrowing dinosaurs in Victoria. But for my faithful readers to better understand the science that preceded that decision, in my next post I’ll provide a brief history of how this whole idea of “burrowing dinosaurs” came together in just the past few years.
(Three peer-reviewed scientific papers that show either end of the “dinosaurs living in burrows” idea are:
(1) Rich, P.V., Rich, T.H., Wagstaff, B.E., McEwen-Mason, J., Douthitt, C.B., Gregory, R.T., Felton, E.A., 1988. Evidence for low temperatures and biologic diversity in Cretaceous high latitudes of Australia. Science, v. 242, p. 1403–1406;
(2) Varricchio, D.J., Martin, A.J., Katsura, Y., 2007. First trace and body fossil evidence of a burrowing, denning dinosaur. Proceedings of the Royal Society of London, B, v. 274, p. 1361–1368;
(3) Martin, A.J. 2009. Dinosaur burrows in the Otway Group (Albian) of Victoria, Australia, and their relation to Cretaceous polar environments. Cretaceous Research, v. 30, p. 1223–1237.)