Friday, December 19, 2014

What ever happened to Brontosaurus?

I have only recently realized that Brontosaurus is no longer a dinosaur. All of my son's books about dinosaurs had the longed-necked sauropod labeled as Apatosaurus, suggesting that something is very different from when I was a kid. Luckily, Brian Switek's book My Beloved Brontosaurus: on the road with old bones, new science, and our favorite dinosaurs explains what happened. Briefly: in 1877, Yale paleontologist O.C. Marsh discovered a partial skeleton of a young dinosaur that he named Apatosaurus; two years later when he found a similar skeleton, he called it Brontosaurus. In 1903, another paleontologist (Elmer Riggs) argued that the differences between the two skeletons were not great enough to warrant two different species. Because Apatosaurus was named first, it had priority for the scientific name. For some unknown reason, this development did not filter down to popular culture or even museums. According to Switek, the changes weren't made until the late eighties. Even after that, it was hard for people to adapt to the change. Switek compares the sadness we experienced at the loss of Brontosaurus with the news that Pluto was no longer a planet.

Brontosaurus stamp from 1989
Switek, a lifelong dinosaur freak, uses what he learned about dinosaurs as a child to illustrate how much our understanding of dinosaurs has changed. In the case of dinosaurs like Apatosaurus, everything we were taught was incorrect: they are no longer considered to be slow creatures, dragging their tails through a semi-aquatic environment. Another major change in our picture of dinosaurs is that they were not scaly like alligators; scientists now think that most, if not all, dinosaurs had feathers. As the connection between dinosaurs and birds is strengthened, scientists have started to consider that the prehistoric creatures may have even been brightly colored like birds. This is another case where the general public is likely to have a tough time adapting its image of Tyrannosaurus rex as a furry rather than a scaly lizard.

Young adult (left) and adult Triceratops skull
Switek also highlights some of the major unanswered questions about dinosaurs, including what sort of developmental changes dinosaurs went through. Interestingly, the well-known Triceratops shows how much dinosaurs may change in their lifetime. The skull on the left is consistent with what we think of as a Triceratops. The skull on the right is also a Triceratops (although for a while it was called a Torosaurus); the difference may simply be age. (Switek digs further into this story for Smithsonian.) Of course, the big question still is: what caused the extinction of the dinosaurs? The author treats this question fairly, discussing where scientists are landing on this issue (most agree that a very large meteor was to blame). Along the way, he also discusses how dinosaurs were not immune to the "slings and arrows of life". Many fossilized dinosaur remains have been diagnosed with pathogens of varying sorts, as well as cancer (as I learned in reading The Cancer Chronicles).

It is a great time to be a dinosaur lover. There have been some really amazing dinosaur finds in the past few years. For instance, for more than fifty years, the 8-foot-long set of arms shown on the right spurred the curiosity of many dinosaur fanatics; in October, researchers published their discovery of a full Deinocheirus skeleton, which was almost as weird as you might have imagined looking at those crazy arms (coverage by Ed Yong). The gigantic sauropod (and not so close relative of the Brontosaurus) called Dreadnaughtus was found in southern Argentina also made headlines due to its great size. Amazingly, this is not the end of the size spectrum for sauropods; size was clearly a huge advantage for these beasts.

The stories of these amazing creatures that dominated the Earth for millions of years are fascinating. Switek's book has inspired me to visit some of the great museums and dig sites in the states.

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