Lessemsaurus

Skeletal reconstruction of Lessemsaurus sauropoides

• Argentina ( Los Colorados Formation)

• Lessemsaurus sauropoides

Lessemsaurus is a basal ( original ) genus of dinosaur sauropodomorphen. This genus is known by a Fund, which comes from the layers of the Los Colorados Formation in northwestern Argentina and includes the fragmentary remains of probably three individuals. He is on the Norian dated ( Upper Triassic ). With a length of approximately nine meters Lessemsaurus belonged to the larger basal representatives of Sauropodomorpha. The genus shows a unique combination of derived (modern) features, which are characteristic for Eusauropoden, as well as plesiomorphic ( original ) characteristics as ( " prosauropods " ) are for non - sauropod characteristic. The genus leads only one way Lessemsaurus sauropoides.

Systematics and Features

The exact relationships of Lessemsaurus are controversial. Bonaparte ( 1999) wrote Lessemsaurus the Melanorosauridae to a group within the Prosauropoda. The group Prosauropoda is not currently accepted by most researchers as a natural group, but declared as paraphyletic and thus rarely used. The validity of the Melanorosauridae itself is currently controversial. Representatives of this group were large, four-legged running Sauropodomorpha that were probably closely related to the sauropods. Pol and Powell ( 2007) describe Lessemsaurus representing the Sauropodomorpha, but forego a more accurate classification. Some recent studies classify Lessemsaurus as basal sauropods.

Lessemsaurus has a number of common features with the early sauropods Antetonitrus, which are absent in non- sauropods, such as a wide dorsal blade of the shoulder blade ( scapula ) and a straight thigh bone ( femur). However, other original features distinguish this genus by the representatives of Eusauropoda; so for example, has the ilium ( ilium ) a well trained ischial peduncle on, a branch of the ilium, which was articulated with the bottom end ansitz ischium ( ischium ). Distinguishing features ( autapomorphies ), the basis of which this genus is distinguished from other genera, include the high vertebral arches of the middle and anterior dorsal vertebrae and the extreme shortening of the first metacarpal bone ( metacarpal ) with a.

Fund, Research History and naming

The find was made ​​in 1971 by paleontologist Jose Bonaparte and colleagues during a paleontological expedition ( the Lillo Palaeontologic expedition ). The first scientific description published Bonaparte in 1999. This description is based only on parts of neck, back and sacral vertebrae, since the other fossils of the discovery were not prepared at the time of publication. A complete description of the remaining fossils was followed in 2007 by Diego Pol and Jaime Powell. These fossils include more vertebrae, shoulder and pelvic girdle, and fore - and hind legs with a. The name Lessemsaurus ( " Lessems lizard" ) honors Donald Lessem, founder of the society " The Dinosaur Society ". The species name sauropoides ( " similar to sauropods " ) points to the similarity of the vortex with those original sauropods.