Nyasasaurus
| Nyasasaurus | ||||||||||||
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| Temporal occurrence | ||||||||||||
| Middle Triassic ( Anisium ) | ||||||||||||
| approx. 245 to 240 million years | ||||||||||||
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Nyasasaurus | ||||||||||||
| Nesbitt et al. , 2013 | ||||||||||||
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Nyasasaurus is a genus of extinct reptiles from the Middle Triassic of East Africa . Fossils of the approximately two to three meter long animal were found in the area around what is now Lake Malawi and are around 240 to 245 million years old (late anisium ). They cameto lightfor the first time in the 1930s during paleontological excavations and in 2013 a group of scientists led by Sterling Nesbitt placed them in their own genus with the only species Nyasasaurus parringtoni . Phylogenetic analyzes of the fossil material classify Nyasasaurus either as a dinosaur or as a closest relative of this group of animals. Its African origin suggests that the dinosaurs originated in southern Pangea , as the genus is about 15 million years older than the oldest known dinosaurs from the early Upper Triassic of South America.
features
Since only a few and fragmented fossils of Nyasasaurus have been found, only a few morphological features of the animals can be determined. The dimensions of the vertebrae suggest a body length of 2–3 m. The upper arm of Nyasasaurus had an elongated crest at its upper end. The animals had at least three sacral vertebrae and had hyposphene-hypantrum connections between the forelumbar vertebrae. Compared to more original dinosaur forms , Nyasasaurus showed accelerated bone growth, which is comparable to that of the early dinosaurs.
Site, fossil material and stratigraphy
The first Nyasasaurus finds , three cervical and two posterior vertebrae, date from the early 1930s. Gordon Murray Stockley found them in the western Manda banks of the Ruhuhu Basin in southwestern Tanzania . The holotype of the genus ( inventory number NHMUK R6856) was uncovered by Francis Rex Parrington in the Lifua layer segment of the Manda benches. It consists of a humerus, three fragmentary back and three sacral vertebrae. The type locality is dated to the late Anisium (around 240 to 245 mya ), so it belongs to the Middle Triassic . Thus, nyasasaurus 10-15 million years older than Eoraptor , one of the oldest known dinosaur from the Ischigualasto Formation of Argentina.
ecology
Since neither the skull nor the running apparatus of Nyasasaurus is known, no conclusions can be drawn about its diet or lifestyle. The large animal fauna in its habitat consisted of the cynodonts Aleodon brachyrhamphus and Scalenodon angustifrons , the dicynodonts Sangusaurus edentatus and Angonisaurus cruickshanki, and the rhynchosaur Stenaulorhynchus stockleyi .
Systematics
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| Systematic position of Nyasasaurus according to Nesbitt et al. (2013). The genus is shown here as the most original branch of the dinosaur ; but it could also be placed outside as its sister taxon . |
One of the fossils now ascribed to Nyasasaurus was first identified in 1932 by Sydney H. Haughton as “? Thecodontosaurus alophos “briefly described . Alan Charig described another specimen in his dissertation (doctoral thesis) in 1956 and placed it in a systematic vicinity of Prestosuchier's Spondylosoma absconditum . Charig also noticed certain similarities in the bone structure with the lizard-pelvis dinosaurs and led the material eleven years later under the name Nyasasaurus parringtonis as a relative of Thecodontosaurus . Neither Haughton nor Charig described their taxa but formally valid , which is why they as nomina nuda apply. In the period that followed, the fossils were listed as prosauropods , as an early representative of the dinosaurs, or as one of their early relatives. In 2013, Sterling Nesbitt , Paul M. Barrett , Sarah Werning and Christian Sidor provided a revision of the material and a formal diagnosis and described it under the name originally proposed by Charig. The genus name Nyasasaurus ("lizard from Nyasasee") is based on the site near Lake Malawi (called Nyasasee in Tanzania), the specific epithet parringtoni honors Francis Rex Parrington, who found the holotype.
In addition, Nesbitt and colleagues come to the conclusion that Nyasasaurus is either the most basal dinosaur or the sister taxon of this group. In particular, the bone crest on the upper arm is a common feature of the dinosaurs. However, the analysis of osteological fine features shows Nyasasaurus for individual features partly as derived , partly as basal dinosaur. For the time being, Nesbitt and colleagues classify the genus as a dinosaur, but also express reservations because the derived and original features of the dinosaurs and the position of some other basal taxa are unexplained.
swell
literature
- Sterling J. Nesbitt, Paul M. Barrett, Sarah Werning, Christian A. Sidor, Alan J. Charig: The Oldest Dinosaur? A Middle Triassic Dinosauriform from Tanzania In: Biology Letters . Vol. 9, No. 1, 2013, ISSN 1744-9561 , pp. 1–5, doi : 10.1098 / rsbl.2012.0949 .
- Sterling J. Nesbitt, Paul M. Barrett, Sarah Werning, Christian A. Sidor, Alan J. Charig: Electronic Supplementary Material. The Oldest Dinosaur? A Middle Triassic Dinosauriform from Tanzania . In: Biology Letters . Vol. 9, No. 1, 2013, pp. 1-54, doi : 10.1098 / rsbl.2012.0949 .
Individual evidence
- ↑ a b Nesbitt et al .: The Oldest Dinosaur? 2013, pp. 2–3.
- ^ Nesbitt et al .: The Oldest Dinosaur? 2013, p. 3.
- ^ Nesbitt et al .: Electronic Supplementary Material. The Oldest Dinosaur? 2013, p. 32.
- ^ Nesbitt et al .: The Oldest Dinosaur? 2013, pp. 1–2.
- ^ Nesbitt et al .: The Oldest Dinosaur? 2013, p. 2.
- ^ Nesbitt et al .: Electronic Supplementary Material. The Oldest Dinosaur? 2013, pp. 3–32.
- ^ Nesbitt et al .: The Oldest Dinosaur? 2013, pp. 1–4.
- ^ Nesbitt et al .: The Oldest Dinosaur? 2013, pp. 3–4.