September 16, 2009
The dig site looked like something out of a Hollywood movie. New dinosaurs are often described from partial, fragmentary skeletons, but the bones of Spinophorosaurus nigerensis made a beautiful circle in the pink rock of the Niger desert. This was the kind of preservation paleontologists dream about, and it was made all the more spectacular by the fact that Spinophorosaurus is an entirely new kind of sauropod.
Described by an international team of scientists in the journal PLoS One, Spinophorosaurus lived during the Middle Jurassic (about 176-161 million years ago). It is the most complete early sauropod yet found. Although not the largest long-necked dinosaur to have ever lived, it still would have been head-and-shoulders above even the tallest human. Yet a few things make this newly-described dinosaur really stand out.
First, it had a wicked set of spikes at the end of its tail. Everyone knows that Stegosaurus had such spikes (technically called “thagomizers” in homage to a Gary Larson cartoon), but fewer people have heard that some sauropods had tail spikes, too. In the case of Spinophorosaurus, it appears that the sauropod had two pairs of large, bony spikes near the end of its tail. This arrangement is similar to that seen in Shunosaurus, a sauropod with a spiked tail club that lived around the same time in what is now China.
Second, Spinophorosaurus will be very important to figuring out how sauropods spread throughout the world during the Jurassic. The researchers found that it was more closely related to the sauropods that lived in Asia than those that inhabited southern continents, potentially putting Spinophorosaurus close to the split between the two groups. It was not the last common ancestor of the two, not by a long shot, but as the authors state, Spinophorosaurus does provide evidence for an evolutionary “connection between North African, European, and East Asian sauropods in the Jurassic.”
More fossil discoveries will be required to test this hypothesis, but there is little doubt that Spinophorosaurus will continue to play an important part in untangling the sauropod evolutionary tree.
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