Nyasasaurus
Nyasasaurus | |
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Life restoration of N. parringtoni | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Clade: | Archosauria |
Clade: | Avemetatarsalia |
Clade: | Ornithodira |
Clade: | Dinosauromorpha (?) |
Genus: | †Nyasasaurus Nesbitt et al., 2013 |
Type species | |
†Nyasasaurus parringtoni Nesbitt et al., 2013
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Synonyms | |
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Nyasasaurus (meaning "
Previously, the oldest record of dinosaurs was from Brazil and Argentina and dated back to the mid-late Carnian stage, about 233.23 to 231.4 million years ago. Nyasasaurus comes from a deposit formerly considered Anisian in age, meaning that it would predate other early dinosaurs by about 12 million years.[1] However, more recent studies cast doubt to this age,[2] pointing out that the deposits would actually be Carnian in age,[3][4] which would considerably reduce this temporal gap.
History of study
In the 1930s, the holotype of Nyasasaurus was collected in Parrington's locality B36 from the Lifua Member of the Manda Formation, Ruhuhu Basin near
The referred specimen of Nyasasaurus, SAM-PK-K10654, was collected by G. M. Stockley in the early 1930s in the western portion of the Manda Formation at Stockley's locality B27.[8] This locality is listed as a locality from the "Upper Bone Bed" of the Manda Formation (currently understood to be from the Lifua Member) by Haughton (1932). The specimen was collected under a single field number, S507, presumably from a small area. The specimen was probably associated as evidenced by the bone quality, color and surrounding matrix (dark gray to black carbonate). The consistent sizes of the remains indicate that they probably represent a single individual.
Stockley's locality B27 is located near the village of Gingama and it was probably the only specimen found at this locality, although a nearby locality B26, also listed as Gingama, produced
The name Thecodontosaurus alophos was coined for this specimen by Haughton (1932).[9] Its holotype consists of three cervical vertebrae and two middle to posterior dorsal vertebrae that are poorly preserved as they are highly fractured and parts of the bone and bone surfaces are eroded. Originally, a comparison of Thecodontosaurus alophos was made only with Coelophysis longicollis. Since then, the species has been largely ignored by all subsequent vertebrate workers and no formal diagnosis of the specimen was ever provided. Nesbitt et al. (2013) found the specimen to not be diagnostic because it does not have any autapomorphic features or a unique combination of characteristics. Therefore, they suggested to abandon the name Thecodontosaurus alophos and to refer its specimen to Nyasasaurus parringtoni.[1]
Description
The
The study also mentioned the similarity between the presacral vertebrae of both specimens of Nyasasaurus parringtoni and those of the enigmatic
An analysis of the interior structure of the humerus indicates that
Classification
Because it is based on incomplete remains, Nyasasaurus has been difficult to classify. It can be placed confidently within
Nyasasaurus was suggested to have been a primitive
Dinosaur affinities of the holotype are supported by the long deltopectoral crest on the humerus, an unambiguously dinosaur top, another feature present only in dinosaurs. The humerus does not share any
Nesbitt et al. (2013) incorporated both specimens, NHMUK R6856 and SAM-PK-K10654, into a phylogenetic analysis. This analysis was based on data from a 2011 analysis by Sterling Nesbitt that included many Triassic archosaurs.[1] When NHMUK R6856 was added to the data set, several possible relationships were found. Various possible evolutionary trees place it as the sister taxon of Dinosauria, the most basal member of Ornithischia (the group that includes most herbivorous Mesozoic dinosaurs), or a member of Theropoda (the group that includes most carnivorous dinosaurs as well as birds). When SAM-PK-K10654 was added to the analysis, it was found to be a theropod. SAM-PK-K10654 possesses several theropod features, including deep pits or fossae in its neck vertebrae, which are not found in NHMUK R6856 because of the limited overlap between the specimens.[1] The following cladogram depicts these possibilities:
Archosauria
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A large phylogenetic analysis of early dinosaurs and dinosauromorphs by Matthew Baron,
In 2021, Fernando Novas and colleagues used the aforementioned characteristics shared by Nyasasaurus and Teleocrater—and not by dinosauriforms such as Asilisaurus and Silesaurus—to suggest that a position for Nyasasaurus in the Dinosauriformes is uncertain. However, they elected not to comment further on Nyasasaurus' affinities given the fragmentary nature of the fossils.[10]
See also
- Eoraptor
- Alwalkeria
- Agnosphitys
- Dinosaur evolution
Contemporaries
References
- ^ PMID 23221875.
- ^ S2CID 226195075.
- ^ PMID 26644579.
- ^ ISSN 0895-9811.
- ^ Charig, A.J., 1956, New Triassic archosaurs from Tanganyika, including Mandasuchus and Teleocrater. Dissertation, Cambridge University
- ^ Charig, A. J. (1967). "Archosauria," in The Fossil Record: A Symposium with Documentation, Geological Society of London pp 708–718
- S2CID 91935861.
- S2CID 129371059.
- S2CID 128417120.
- ^ .
- ^ Ginsburg, L., 1986, "Régressions marines et extinction des Dinosaures", Les Dinosaures de la Chine à la France, Colloque International de Paléontologie, Toulouse, France, 2-6 Septembre 1985; Muséum d'Histoire Naturelle de Toulouse, Toulouse pp 141-149
- S2CID 83493714.
- ^ "New contender for oldest dinosaur". 4 December 2012. Retrieved 4 December 2012.
- ^ Baron, Matthew (5 February 2018). The Origin and Early Evolution of the Dinosauria (PhD). Retrieved 7 April 2022.
Bibliography
- Lambert, David (1994). The Encyclopedia of Dinosaurs. Bloomsbury Books p 80.
External links
- Oldest Dinosaur Found from Discovery.com
- Discussion of "Nyasasaurus" from the Dinosaur Mailing List
- The oldest dinosaur: working from scraps - The Economist