Lessemsaurus
| Lessemsaurus | ||||||||
|---|---|---|---|---|---|---|---|---|
Skeletal reconstruction of Lessemsaurus sauropoides |
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| Temporal occurrence | ||||||||
| Upper Triassic ( Norium ) | ||||||||
| 228 to 208.5 million years | ||||||||
| Locations | ||||||||
| Systematics | ||||||||
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| Scientific name | ||||||||
| Lessemsaurus | ||||||||
| Bonaparte , 1999 | ||||||||
| Art | ||||||||
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Lessemsaurus is a basal (original) genus of the sauropodomorphic dinosaurs . This genus is known from a find that comes from the layers of the Los Colorados Formation in northwestern Argentina and includes the fragmentary remains of probably three individuals. It is dated to the Norium ( Upper Triassic ). With a length of approximately nine meters, Lessemsaurus was one of the larger, more basal representatives of the Sauropodomorpha. The genus shows a unique combination of derived (modern) traits, as theyare characteristic of Eusauropods , as well as of plesiomorphic (original) traits, as they are characteristic of non-sauropods (" prosauropods "). The genus only has one species , Lessemsaurus sauropoides .
Systematics and characteristics
The exact relationship of Lessemsaurus is controversial. Bonaparte (1999) attributed Lessemsaurus to the Melanorosauridae , a group within the Prosauropoda . The group Prosauropoda is currently not accepted by most researchers as a natural group, but declared as paraphyletic and therefore rarely used. The validity of the Melanorosauridae themselves is currently controversial. Representatives of this group were large, four-legged sauropodomorpha, which were probably closely related to the sauropods. Pol and Powell (2007) describe Lessemsaurus as a representative of the Sauropodomorpha, but dispense with a more precise classification. Some recent studies classify Lessemsaurus as a basal sauropod.
Lessemsaurus has a number of common characteristics with the early Sauropoden antetonitrus , which are absent in non-Sauropoden, such as a wide dorsal blade of the shoulder blade (scapula) and a straight femurs (femur). However, other original features distinguish this genus from the representatives of the Eusauropoda; for example so, the ilium (Ilium) a well trained ischial peduncle on a branch of the iliac bone, which with the end ansitz below ischial was articulated (ischium). Distinguishing features ( autapomorphies ) by which this genus is distinguished from other genera include the high vertebral arches of the middle and anterior vertebrae and the extreme shortening of the first metacarpal bone (metacarpal I).
Find, 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 was published by Bonaparte in 1999. This description is based only on parts of the cervical, back and sacrum vertebrae, since the remaining fossils of the find had not yet been prepared at the time of publication. A full description of the remaining fossils followed in 2007 by Diego Pol and Jaime Eduardo Powell . These fossils include additional vertebrae, shoulder and pelvic girdles, and front and rear legs. The name Lessemsaurus ("Lessems Echse") honors Don Lessem , the founder of "The Dinosaur Society". The species name sauropoides ("comparable to sauropods") indicates the similarity of the vertebrae with those of original sauropods.
Individual evidence
- ^ Gregory S. Paul : The Princeton Field Guide To Dinosaurs. Princeton University Press, Princeton NJ et al. 2010, ISBN 978-0-691-13720-9 , p. 170, online .
- ↑ a b c José F. Bonaparte : Evolución de las vértebras presacras en Sauropodomorpha. In: Ameghiniana. Vol. 36, 1999, ISSN 0002-7014 , pp. 115-187, online .
- ↑ Peter Galton , Paul Upchurch : Prosauropoda. In: David B. Weishampel , Peter Dodson , Halszka Osmólska (eds.): The Dinosauria . 2nd edition. University of California Press, Berkeley CA et al. 2004, ISBN 0-520-24209-2 , pp. 232-258.
- ^ A b c d Diego Pol, Jaime E. Powell: New information on Lessemsaurus sauropoides (Dinosauria: Sauropodomorpha) from the Upper Triassic of Argentina. In: Paul M. Barrett , David J. Batten (eds.): Evolution and palaeobiology of early sauropodomorph dinosaurs (= Special Papers in Palaeontology. Vol. 77). The Palaeontological Association, London 2007, ISBN 978-1-4051-6933-2 , pp. 223-244.
- ^ Paul Upchurch, Paul M. Barrett, Peter M. Galton: A phylogenetic analysis of basal sauropodomorph relationships: implications for the origin of sauropod dinosaurs. In: Paul M. Barrett, David J. Batten (eds.): Evolution and palaeobiology of early sauropodomorph dinosaurs (= Special Papers in Palaeontology. Vol. 77). The Palaeontological Association, London 2007, ISBN 978-1-4051-6933-2 , pp. 57-90.
- ^ Adam M. Yates, Matthew F. Bonnan, Johann Neveling, Anusuya Chinsamy, Marc G. Blackbeard: A new transitional sauropodomorph dinosaur from the Early Jurassic of South Africa and the evolution of sauropod feeding and quadrupedalism. In: Proceedings of the Royal Society. Series B: Biological Sciences. Vol. 277, No. 1682, 2010, ISSN 0950-1193 , pp. 787-794, doi : 10.1098 / rspb.2009.1440 .