More dinosaurs!

24 04 2007

As if you all hadn’t heard enough about dinosaurs already, yesterday I received Louie Psihoyos’/John Knoebber’s beautiful book Hunting Dinosaurs in the mail. You’re probably familiar with Psihoyos’ work; many of his photographs, especially of dinosaurs and other paleontological curiosities, have been featured in National Geographic. Indeed, the entire book reads like a National Geographic article, gorgeous full page illustrations being plentiful and diverse. Rather than trying to reinvent the wheel when it comes to “dinosaurology” Psihoyos & Knoebber travel around the globe to ask the experts themselves about their discoveries, contributions, and controversies, ranging from wise and humble octogenarians to folks who should never be allowed to touch a fossil ever again.

Highlights of the book include Edward Drinker Cope’s traveling skull and the quest of Psihoyos and Bob Bakker to get Cope’s remains listed as the type specimen for Homo sapiens, an ankylosaur trackway that disappeared overnight, and the destructive field and lab techniques of Jose Bonaparte (a perfect sauropod egg and massive neck vertebrae both lost before the author’s eyes because of Bonaparte’s ineptitude). It is refreshing to get a look at the people who are actually hunting dinosaurs, whether they be superstars like Jack Horner, Bob Bakker, and Paul Sereno or great “unsung heroes” like Jack McIntosh, Giuseppe Leonardi, and Armand de Ricqles; self-made paleontologists and Harvard grads have all contributed to our understanding of prehistory.

One of the things I appreciate most about the book is Psihoyos’ photography techniques when dealing with museum mounts; photographing his subjects at night with subtle lighting that makes the skeletons appear as if they are walking out of the shadows and into the moonlight. While the AMNH’s dinosaurs are now bathed in sunlight, contrasting sharply against the bright walls, I remember my first visits as a child, looking up at the beast then known as Brontosaurus. In that dim room, I didn’t need dynamic posing or a life reconstruction; my little 8-year-old brain was so struck by the immensity of the skeleton that I thought I could hear the ghost of the animal breathing. Psihoyos clearly appreciates just this sort of encounter, the Jungian mystery of the dragon, and hence I love the book all the more.

The book also reminded me of a controversy that has lain dormant for some time; the rearing Barosaurus in the Grand Rotunda of the AMNH. Personally, I think the reconstruction is a bit more fantasy to drum up museum attendance (and it surely did) than it is sound science. While we know that large sauropods would have to rear up, even for a moment, at least once in their adult lives to mate (and I’m surprised I have so seldom heard this point, most discussions being based around feeding), I don’t find the defensive posture of a protective parent especially compelling. The scene being reenacted for museum patrons is an Allosaurus threatening a mother and baby Barosaurus, the mother standing upright in defense. In doing so, she exposes her entire belly to the attaching predator, her forearms being too short to be especially effective. Then there’s the issue of all that weight (the majority of the sauropod, from head to hips) being brought upright and resting on the hips, which must have been a mighty strain. This is all assuming, of course, that the dinosaur could raise its head up so high in an instant without blacking out, something even modern giraffes have trouble doing (which is why they often take their time to get up). While I’m not going to be dogmatic and say “This sort of thing never happened I think it has far too many problems to be put out as the best science we can offer the public, although hopefully the debate over the issue will heat up again and maybe some new discoveries will help shed light on the issue.

The pose also got me thinking about predatory dinosaurs and their primary prey; while it is exciting to envision a pack of Allosaurus going after a huge adult sauropod, I don’t think this was the common hunting method. Big predators today, be they sharks in the sea or lions on land, tend to try and isolate an immature, old, wounded, or sickly individual which they are more likely to catch and kill quickly (lessening the chance of injury to themselves). Even for a pack of Allosaurus, taking down an adult sauropod would be a dangerous proposition that may very well have gotten them injured or killed. Thus, I think the highest mortality due to predation among sauropods was among the young, and I don’t know if the record concurs, but this could be why we don’t find many immatures. It’s also important to keep in mind that when a large, adult sauropod died (and there seems to have been plenty) it would have been a bonanza for predators, who then would be in competition to get control of the carcass. Modern-day Africa would be a fair analog, lions dominating kills (although they can be driven off by a group of the #2 predators, spotted hyenas), with leopards and wild dogs following, leaving cheetahs as they animals that can nearly always been driven from a kill (hence their daytime hunting habits to avoid competition). This is a fairly simple hypothesis, and this isn’t to say that active hunting of adult sauropods never happened, but I think scavenging and preying on the young was far more common than the classic battle scenes that are staples of many popular works on dinosaurs.

I also want to make sure I take time to recommend Chris McGowan’s book Dinosaurs, Spitfires, and Sea Dragons, a great follow-up to Bob Bakker’s The Dinosaur Heresies. McGowan takes plenty of time to walk the reader through simple explanations of physics and metabolism that are important to understand why dinosaurs looked and acted the way they did, and I think he does a great job outlining the warm-blooded vs cold-blooded debate. There is no doubt that dinosaurs were active, dynamic animals that maintained a high (and near-constant) body temperature, but how they achieved this is not an either-or question. There are ways to be an active animal without having to have a high metabolic rate like extant mammals, and perhaps having a high metabolic rate in certain environments may have even been detrimental (it’d be far easier to overheat, for one thing). Indeed, McGowan is often frank in his discussions about what we do know and what we don’t know, and raises the point that perhaps different groups of dinosaurs evolved different metabolic strategies over their long tenure on earth. While there is no longer any reason to doubt that dinosaurs were active and often energetic creatures, I think there’ still plenty of room for research and debate as to how they achieved this and the warm-blooded vs cold-blooded terminology creates a bit of a false dichotomy (which makes it easy for one side to mischaracterize another).

In any event, I would heartily recommend that anyone with even a passing interest in dinosaurs pick up Psihoyos’ book, and for those who want a frank general view of dinosaur (and icthyosaur & pterosaur) mechanics McGowan’s is a must. I can only imagine what still is in the ground, lying dormant not knowing the dinosaur revolutions it may start. We really are living in a golden age of paleontology, and even if we didn’t find any more fossils there’d still be plenty of work to be done with what we’ve got.




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