Chinshakiangosaurus
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Chinshakiangosaurus Temporal range: Early Jurassic |
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| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Sauropsida |
| Superorder: | Dinosauria |
| Order: | Saurischia |
| Suborder: | Sauropodomorpha |
| Infraorder: | Sauropoda |
| Family: | unknown |
| Genus: |
Chinshakiangosaurus Ye vide Dong, 1992 |
| Binomial name | |
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Chinshakiangosaurus chunghoensis Ye vide Dong, 1992 |
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Chinshakiangosaurus (meaning "Chinshakian lizard") is a genus of dinosaur and probably one of the most basal sauropods known. The only species, Chinshakiangosaurus chunghoensis, is known from a fragmentary skeleton found in Lower Jurassic rocks in China. Chinshakiangosaurus is one of the few basal sauropods with preserved skull bones and therefore important for the understanding of the early evolution of this group. It shows that early sauropods may have possessed fleshy cheeks.
Like all sauropods, it was a large, quadrupedal herbivore with long neck and tail. The body length of the only specimen is estimated at 12 to 13 meters. The remains consists of the dentary (the tooth bearing bone of the mandible) including teeth as well as several parts of the postcranium. By now, only the dentary and the teeth were studied extensively; the remaining skeleton still awaits a proper description.
The dentary was curved in dorsal view, so that the mandibles formed a U-shaped, broad snout. This feature is typical for sauropods – in Prosauropods, on the contrary, the dentary was straight, forming a V-shaped, tapered snout. Paul Upchurch and colleagues (2007) suppose that this differences may can give hints about feeding habits: The prosauropods with their tapered snouts possibly where selective feeders, who ate only certain plant parts, whereas sauropods with their broad snouts where bulk feeders, adapted to consume large amounts of foliage.
The tooth size increased towards the tip of the snout, like in sauropods. Another derived, sauropod like feature was a bony plate that lined the tooth row laterally and became thicker towards the tip of the snout. This plate may have hindered the teeth to be displaced while defoliating plants.
The dentary was deep. However, as in prosauropods, it became lower towards the tip of the snout, while in sauropods the dentary became deeper, forming a very deep symphysis. In lateral view, the dentary shows a prominent ridge running diagonally across the bone. Apart from Chinshakiangosaurus, this feature is only known from prosauropods, where it is interpreted as the insertion point of a fleshy cheek. Such cheeks would have prohibited food falling out of the mouth and may be a hint that the food underwent some degree of oral processing before it was swallowed. If Chinshakiangosaurus indeed was a basal sauropod, this would be the first evidence of cheeks in this group. In all other sauropods known from congruous remains this feature had been reduced already.
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Wikipedia