Massospondylus, prosauropods that lived during the Early Jurassic

Canadian Museum of Nature

MASSOSPONDYLUS (MASS-oh-SPON-die-luss)

Period: Early Jurassic

Order, Suborder, Family: Saurischia, Sauropodomorpha, Plateosauridae

Location: Africa (South Africa, Zimbabwe), North America (United States)

Length: 13 feet (4 meters)

Massospondylus was a medium-size prosauropod. Sir Richard Owen named the animal in 1854. Its name means "massive vertebrae." There are many skeletons of this animal, including several good skulls from South Africa and one good skeleton from the Kayenta Formation of Arizona. The Kayenta skull is about 25 percent bigger than the biggest African specimen. Some of the smaller skulls from South Africa were likely juveniles. They had taller, narrower skulls with bigger eye sockets. This shows that the skull proportions changed as it grew.

The skull of Massospondylus was shallower and shorter than that of Plateosaurus, with more changes along the tooth row. The front teeth were round, but the back teeth were more oval. The lower tooth row was shorter than the upper. Because of this difference in jaw length, and the unusual wear on the front teeth of the upper jaws, Massospondylus might have had a small lower beak to cut vegetation. The teeth and jaws of Massospondylus were built for a diet of plants.

Several of the South African specimens of Massospondylus had rounded stones in or near their ribcages. These appear to have been used to grind food in the stomach, much like the gizzards of birds. Several sauropods had similar structures. These "stomach stones" were smooth and polished, as if by digestive acids or grinding against other stones and plant material.

The proportions of the skeleton of Massospondylus suggest that it, like Plateosaurus, could rear up and possibly walk on its hind legs. Massospondylus had an enlarged thumb claw that could have been used as a grooming tool or to dig or grasp food.

Many prosauropod dinosaurs have been found in the Late Triassic and Early Jurassic formations of Africa and North America. The Massospondylus from Arizona, however, provided the first proof of a prosauropod from both continents. The theropod Syntarsus and the early crocodilian Protosuchus were on both continents, as were some primitive mammals. This is evidence that climate and land barriers were absent up to the Early Jurassic. This suggests that many animals of the time could live all over the world.