Utatsusaurus

From Wikipedia, the free encyclopedia

Utatsusaurus Fossil range: Middle Triassic
life restoration of Utatsusaurus hataii
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Sauropsida Superorder: Ichthyopterygia Family: Utatsusauridae McGowan & Motani, 2003 Genus: Utatsusaurus
Binomial name
Utatsusaurus hataii Shikama, Kamei & Murata, 1978

Utatsusaurus is the earliest-known form of an ichthyopterygian (the group of marine reptiles that includes the ichthyosaurs), who lived in the middle Triassic period (c. 240-230 millions years ago). Unlike the more advanced icthyosaurs, Utatsusaurus has no dorsal fin and has a broad skull that tapers slowly toward the snout.

For the size of the skull, the teeth are rather small, and arranged in a primitive groove. Utatsusaurus had small fins, with four toes instead of the usual five found in primitive ichthyosaurs. The tail had a long low fin, suggesting that the animal swam by undulation, rather than using its paddles and tail. Feeding on a diet of fish, Utatsusaurus reached a length of 3 meters (10 feet).

Ryosuke Motani from the University of California, Berkeley and Nachio Minoura from Hokkaido University re-examined the fossils of Utatsusaurus in 1998 using computer imagery to reverse the distortion of the original skeleton. They found that Utatsusaurus was closely related to the lizard-like diaspid reptiles such as Petrolacosaurus, making ichthyopterygians a distant relative to lizards, snakes and crocodiles.

[edit] References

Dixon, Dougal. "The Complete Book of Dinosaurs." Hermes House, 2006.