New dinosaur rears its head

The remains of a new herbivorous sauropod dinosaur, discovered near the world-famous Carnegie Quarry in Dinosaur National Monument, may help explain the evolution of the largest land animals ever to walk the earth.

University of Michigan paleontologist Jeffrey Wilson and graduate student John Whitlock, along with coauthors from Brigham Young University and Dinosaur National Monument, describe the new species in a paper published online Feb. 24 in the journal Naturwissenschaften.

The discovery represents a rare look at a sauropod skull, known for only a handful of the more than 120 species known to science. Skulls are important, because they can tell scientists a lot about what and how an animal ate.

'At first glance, sauropods don't seem to have done much to adapt to a life of eating plants,' said Wilson, an assistant professor of geological sciences and an assistant curator at the U-M Museum of Palaeontology. 'They don't have some of the obvious hallmarks of herbivory seen in other dinosaurs, like beaks for slicing or cheeks to hold in food while chewing. They were obviously quite proficient at eating, though, and every skull gives us a few more pieces of the puzzle.'

Together with palaeontologists Brooks Britt (Brigham Young University) and Dan Chure (Dinosaur National Monument), Wilson and Whitlock compared the skulls and teeth of the new dinosaur to those of other sauropods and discovered one repeated trend throughout sauropod evolution: the development of narrow, pencil-like teeth from broad-bladed teeth.

'We know narrow-crowned teeth appear at least twice throughout sauropod history, and both times it appears to correspond to a rise in the number of species,' Whitlock said. 'This new animal is intermediate in terms of its tooth shape and helps us understand how and when one of these transitions occurred.'

Exactly what this means for sauropod diets isn't clear, but the team has uncovered some clues.

'Narrow-crowned teeth are smaller than broad-bladed teeth, and for animals that continually replace their teeth throughout their lifetime, size can be an important factor in how fast that replacement happens,' Wilson said. Faster-replacing teeth, the team thinks, are a biological response to high rates of tooth wear, possibly caused by shifts in diet or behaviour.