The Virtual Art Show: Part 4

Arizonasaurus babbitti

Although Arizonasaurus has been known since 1947, a clear picture of the beast was not provided until 2002, when a nearly complete skeleton was unearthed in—you guess it—Arizona. The new material revealed a spectacular dorsal sail formed by the neural spines of the vertebrae, a strangely persistent feature throughout tetrapod evolution. The skull is large and filled with vicious, recurved teeth. Arizonasaurus would have been a formidable predator. Sails have appeared in virtually every major group of tetrapods, including amphibians, pre-mammalian synapsids, several dinosaur groups, and even some modern chameleons!

The function of dorsal sails remains a mystery. It was once thought that, among cold-blooded animals like Dimetrodon, the sail helped to gather heat. And indeed, this may be true. But in larger, potentially endothermic animals, the sails may have been used primarily as display devices, almost like living billboards advertising an animal's presence. If the solar panel function is the primary one, though, one would expect to see more cold-blooded animals with sails. But while sails occur independently among several tetrapod lineages, they are quite rare overall.

Artist Notes

Arizonasaurus made it into the show more by sloth than anything else. In fact, you may recognize it from a previous post. We threw this sailbacked poposaur in because, most importantly, the work was already done, and second, we felt we needed another piece. Looking back, we probably didn't, but the addition of a sail-backed member of the Crurotari certainly brought some flash to the show. Arizonasaurus has the distinction of being the single piece resulting from a collaboration between Scott and I. A loooong time ago, back in Version 1.0 of this blog (now defunct and deleted--thanks, Google!), I did a fairly lengthy post about crurotarsians, and the centerpiece for that post was the inked drawing of Arizonasaurus, shown below. That picture, however, failed to really "pop," so I begged Scott to color it for me using his latent psychic powers and knowledge of com-poo-tors. He did a wonderful job.

Fun Facts

Arizonasaurus' sail is strange to me. It doesn't really rise until it gets past the shoulderblades, giving it a somewhat abbreviated appearance. This is in contrast to animals like Dimetrodon and Ouranosaurus, who have sails that begin at or cranially to the scapulae. Arizonasaurus also has unusually flared neural spines, meaning that there wasn't a whole lot of skin between the vertebrae of the sail. Again, this is unlike Dimetrodon and Edaphosaurus, who had spike-like neural spines. Many other sailbacked tetrapods had flared neural spines though, including Platyhystrix (an amphibian) and Spinosaurus. One wonders if there was a functional difference between these constructions, or just different ways of building the same structure?

For more Virtual Art Show fun, click the "Virtual Art Show" tag, because I'm too lazy to link to all the individual entries. Scott has several of his own pieces up at Coherent Lighthouse, too, so be sure to check those out! And Raven--all you've gotta do is Tupandactylus! Get on it!