Utatsusaurus ( lat. Utatsusaurus ) is a genus of extinct marine reptiles from the order of ichthyopteries (a taxon that included ichthyosaurs ), the oldest [1] and primitive representative of this group. The name is given at the place where the remains were first found, and means "lizard from Utatsu" ( Greek σαῦρος - lizard, lizard). It was a reptile with a short head, a narrow muzzle and small fins [2] .
| † Utatsusaurus | ||||||||||||||||||
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 Reconstruction of the intravital appearance of Utatsusaurus hataii | ||||||||||||||||||
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| Utatsusaurus (Shikama et.al., 1978 ) | ||||||||||||||||||
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Content
Systematics, relationships with related taxa
This is a derivative genus from the sister taxon to the genus of mesosaurs Wumengosaurus , the sister taxon to the same utatsosaurus was the genus Hupehsuchus . He was larger than the first of the mentioned genera, he had a longer and lower rostrum, had more teeth, they were smaller in size. Its postorbital region was higher, the lacrimal bone was longer, and the scales were deeper [3] .
General information
Utatsuzavr, undoubtedly - an important page in the fossil record, especially its aspects directly related to the history of the development of marine reptiles. After all, it is he who is considered the first representative of ichthyosaurs that has ever lived on Earth, and sometimes he performs for specialists the function of a certain model that captures all the basal (primitive) properties. Among them, the properties of the skeleton, typical of diapsids , a group that now includes lizards and originated with the appearance of the first real reptile - petrolacosaurus . The Utatsuzavr was not so well adapted to life at sea as the later ichthyosaurs - for example, it lacked a dorsal fin and its tail bent down, which led to an uneven distribution of the caudal vertebrae [4] , and besides, in contrast to the more advanced forms of this detachment , it was inflexible [2] .
But the utatsusaurus, nevertheless, was not, most likely, the defining primitive form, since its fins had four fingers, instead of the usual five in other early ichthyosaurs. This suggests that the utatsusaurus was probably on a particular evolutionary line that led to transitional ichthyosaurs, such as the mixosaurus , which had three fingers, like advanced forms, such as the ichthyosaurus itself . And only because of this the utatsusaurus remains extremely important for specialists in studying their evolution of ichthyosaurs [4] .
The skull of the utatsusaurus is extremely wide, especially in comparison with those of other representatives of the ichthyosaurs (especially the shastasaurs , who, as you know, had a very narrow skull), this property inherited from these distant land ancestors. The teeth with which his jaws were strewn can tell us that the diet of the utatsuzavr was fish, although it is quite likely that at times it could feast on cephalopods and even smaller marine reptiles [4] [5] .
Despite all its primitiveness, it was a fairly large ichthyosaur: it reached three meters in length, or, in other words, 18 feet [5] (in some sources a shorter length was indicated: about 10 feet [2] ), and weighed a whole ton [ 5] (500 pounds [2] ). However, in some other sources it is indicated that, on the contrary, it differed from its later relatives in its size, and, being, for example, ten times smaller than the shonizaur , in length reached only one and a half meters [1] .
Places and antiquities of finds
Utatsuzavr was discovered by Japanese paleontologists Shikama, Kamei and Murat ( born Shikama, Kamei & Murata ), in 1978 . Nevertheless, his remains are found not only in Japan, but also in Canada , they are found in sediments of the Olenek layer of the early Triassic era . He lived on our planet about 240-230 million years ago [4] , some sources indicate a more accurate interval: 251.3-247.2 million years ago [6] .
This genus is monotypic, includes only one species - U. hataii (type) [4] . Currently, there are two single collections of the remains of this lizard in the world [6] .
Notes
- ↑ 1 2 I know the world: The history of life on Earth / Pintal T. Yu .. - M .: "Publishing house AST", 2004. - P. 194. - 512 p. - ISBN 5-17-024940-3 .
- ↑ 1 2 3 4 Bob Strauss. Utatsusaurus (English) . dinosaurs.about.com . Date of treatment October 17, 2013.
- ↑ Utatsusaurus and Grippia, two basal ichthysaurs . reptileevolution.com . Date of treatment October 17, 2013.
- ↑ 1 2 3 4 5 Utatsusaurus . prehistoric-wildlife.com . Date of treatment October 17, 2013.
- ↑ 1 2 3 Utatsusaurus - Dinopedia . dinosaurs.wikia.com . Date of treatment October 17, 2013.
- ↑ 1 2 Paleobiology Database: Utatsusaurus . paleodb.org . Date of treatment October 17, 2013.
Literature
- Dixon D. The Complete Book of Dinosaurs. - Hermes House, 2006.
Links
- Wikimedia Commons has media related to Utatsuzavr