Massospondylus
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 Massospondylus at the Natural History Museum, London.
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Extinct (fossil)
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Massospondylus (Greek 'elongated vertebra'), formerly known as Aristosaurus, was an Early Jurassic Period prosauropod, although, if Aetonyx is the same as Massospondylus, it lived from the Late Triassic as well. It was probably a plant eater (herbivore), although it is speculated that the prosauropods may have been omnivorous. This dinosaur was named by Sir Richard Owen in 1854, from remains found in South Africa. It is thus one of the first dinosaurs to be named.
Fossils have since been found in Arizona's Kayenta Formation, South Africa and Zimbabwe.
[edit] Paleobiology
Massospondylus was fairly large for a prosauropod at 6.1 meters (20 feet) long, about 5 feet tall and had an 8-foot long tail. Although long assumed to have been quadrupedal, a recent anatomical study of the forelimbs has questioned this, arguing that their range and motion precludes effective habitual quadrupedal gait.[1]
The animal was a typical prosauropod in most other respects. It possessed a large body and long neck, a small head and almost circular eye sockets. Teeth in the lower jaw were not as long as those in the upper jaw. There also seems to be some variation of tooth morphology, based upon the tooth's position in the jaw, although this is not as pronounced as the specialization of teeth in Heterodontosaurus. Teeth occupying a position closer to the front of the snout were rounder than the more oval-shaped back teeth. Interestingly, the skull of the Arizona specimen is 25% larger than the largest skull from any African specimen. Gastroliths have been found in Massospondylus fossils.
[edit] Reproduction
In the 1970s, six 190-million year old Massospondylus eggs were found, in Golden Gate Highlands National Park in South Africa by James Kitching, who identified them as belonging most likely to Massospondylus. It took nearly 30 years before extraction was started on the fossils of the 6 inch embryos. They remain the oldest dinosaur embryos ever found. Notably, the near-hatchlings had no teeth, suggesting they had no way of feeding themselves. Scientists speculate that after-birth care might have been necessary. The four legs of the near-hatchlings were of equal length. The tail was short and the head over-sized. This suggests a different pattern of development for dinosaurs from that which had previously been thought.
[edit] References
- ^ Bonnan M, Senter P. (2007). Were the basal sauropodomorph dinosaurs Plateosaurus and Massospondylus habitual quadrupeds?; pp. 139-155 in Barrett, P.M. and Batten, D.J. (eds.), Evolution and Palaeobiology of Early Sauropodomorph Dinosaurs. Special Papers in Palaeontology 77.
