Staurikosaurus
Staurikosaurus | |
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Reconstructed skeleton | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Clade: | Dinosauria (?) |
Clade: | Saurischia (?) |
Family: | †Herrerasauridae |
Genus: | †Staurikosaurus Colbert, 1970
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Species: | †S. pricei
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Binomial name | |
†Staurikosaurus pricei Colbert, 1970
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Synonyms | |
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Staurikosaurus (Pronounced "STORE-ee-koh-SAWR-us", "Southern Cross lizard") is a genus of herrerasaurid[1] dinosaur from the Late Triassic of Brazil, found in the Santa Maria Formation.
Description
Colbert (1970) described Staurikosaurus as a small and agile, bipedal predator.[2] Staurikosaurus lived during the late-Carnian and early-Norian stage, of the Late Triassic, approximately 225 million years ago—which makes it one of the earliest dinosaurs known. Its length is measured at 2.2–2.25 metres (7 ft 3 in – 7 ft 5 in) long,[3] but Gregory S. Paul presented a lower length estimate of 2.1 metres (6 ft 11 in) and a body mass estimate of 12 kilograms (26 lb).[4] Staurikosaurus was small in comparison to later theropods like Megalosaurus. The type specimen has long but relatively slender limb bones.
There exists a very incomplete fossil record of Staurikosaurus, consisting of most of the spine, the legs and the large lower jaw. However, dating from such an early period in the dinosaurs' history and being otherwise so primitive, most of Staurikosaurus' other features as being primitive also can be reconstructed. For example, Staurikosaurus is usually depicted with five toes and five fingers[5]—very simple features of an unspecialized dinosaur. However, since the skeletal structure of the legs is known, it can be seen that Staurikosaurus was a quick runner for its size. It also had just two vertebrae joining the pelvis to the spine, a distinctly primitive condition.
The available teeth for Staurikosaurus bear a morphology that strongly suggests a carnivorous diet. The teeth are all serrated, laterally compressed, and caudally curved (i.e. the top of each tooth is curved back toward the throat).[6] This dentition suggests that Staurikosaurus could catch and hold prey, as well as slice and tear flesh to aid in mechanical digestion.[7]
The tail of Staurikosaurus was relatively long (with more than 40 vertebrae) compared to the rest of its body and was held straight and off the ground as it ran. The rear part of Staurikosaurus's tail is stiffened by features of the tail vertebrae. Ostrom (1969a) considered this adaptation to serve as a dynamic stabilizer facilitating the animal's leaping and running.[8]
A diagnosis is a statement of the anatomical features of an organism (or group) that collectively distinguish it from all other organisms. Some, but not all, of the features in a diagnosis are also autapomorphies. An autapomorphy is a distinctive anatomical feature that is unique to a given organism or group. According to Sues (1990), Staurikosaurus can be distinguished based on the following 14 features: (i) a
Discovery and occurrence
Staurikosaurus means "Southern Cross" (after the star constellation visible from the Southern Hemisphere) and "Lizard" (from the Greek work "saurus" meaning lizard), thus "Southern Cross Lizard." The species name pricei is in the honor of Colbert's fellow paleontologist Llewellyn Ivor Price.
The first known specimen of Staurikosaurus (MCZ 1669) was recovered from the
Classification
Later research by Sues et al. (2011) supports that Staurikosaurus and the related genus Herrerasaurus are theropods and evolved after the sauropod line had split from the Theropoda.[13] Mortimer points out that Benedetto (1973) and Galton (1985) were the first to recognize that Staurikosaurus and Herrerasaurus were more closely related to each other than to sauropodomorphs or avepods, placing them both in the Herrerasauridae and Herrerasauria.[14][15][16] Staurikosaurus differs from Herrerasaurus because of its considerably smaller size (femur length of 23 centimetres (9.1 in) vs. 47 centimetres (19 in)). Sereno et al. (1993) concluded that Staurikosaurus was not a theropod and considered it a basal saurischian outside Theropoda and Sauropodomorpha.[17]Staurikosaurus was originally incorrectly assigned by Colbert to Palaeosauriscidae, a defunct family based largely on Efraasia, a prosauropod dinosaur. All major phylogenetic analyses since 1994 have assigned Staurikosaurus to the clade Herrerasauridae, which is the current scientific consensus on classification of this genus. Bittencourt and Kellner (2009) stated that the phylogenetic position of Staurikosaurus is constrained by its close relationship with Herrerasaurus ischigualastensis, which is more complete and well known.[6] Below is a cladogram based on the phylogenetic analysis conducted by Sues et al. in 2011, showing the relationships of Staurikosaurus:[13]
Theropoda |
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Related genera
Staurikosaurus was placed in the clade
Synonyms
The controversial
The synonymy is commented in two subsequent papers, which cast doubt in the association of "Teyuwasu" with Staurikosaurus. In the first paper, the authors only mention that the holotype of "Teyuwasu" is not well preserved, and thus cannot be attributed to Staurikosaurus.[26] In the second, the authors argue that several of the five character states cited to unite the taxa are present in immature specimens of other dinosauriforms.[27] However, the combination (that is, the simultaneous presence) of the five characters listed by Garcia et al.[12] is not present in any of the aforementioned dinosauriforms, and therefore remains unique between "Teyuwasu" and Staurikosaurus.[citation needed]
Therefore, further investigations are needed in order to whether confirm or not the synonymy between "Teyuwasu barberenai" and Staurikosaurus pricei.
Paleobiology
Feeding
Staurikosaurus was a small but active bipedal predator, that preyed on small and medium-sized terrestrial vertebrates such as
Paleoecology
During the Late Triassic dinosaurs played only a minor role in terrestrial life; a fact that would change by the Early Jurassic. Staurikosaurus coexisted with large
References
- S2CID 8349110.
- ^ a b c Colbert, E. H. (1970). A Saurischian dinosaur from the Triassic of Brazil. AM. MUS. NOVITATES 2405; 1-39
- ^ Grillo, O.N. and Azevedo, S.A.K. (2011). "Recovering missing data: estimating position and size of caudal vertebrae in Staurikosaurus pricei Colbert, 1970." Annals of the Brazilian Academy of Sciences,
- OCLC 985402380.
- ^ ISBN 0-7853-0443-6.
- ^ a b c d Bittencourt, J.S. & Kellner, A.W.A., 2009. The anatomy and phylogenetic position of the Triassic dinosaur Staurikosaurus pricei Colbert, 1970. Zootaxa 2079, 1–56.
- ^ a b Langer, M. C., 2004, Basal Saurischia, Chapter Two: In: The Dinosauria, Second Edition, edited by Weishampel, D.B., Dodson, P., and Osmolska, H., California University Press, p. 25-46.
- ^ J. H. Ostrom. 1969. Osteology of Deinonychus antirrhopus, an unusual theropod from the Lower Cretaceous of Montana. Peabody Museum Bulletin 30:1-165
- ^ Sues, 1990. Staurikosaurus and Herrerasauridae. in Weishampel, et al. (eds.). The Dinosauria. University of California Press, Berkeley, Los Angeles, Oxford. 143-147.
- ^ Novas, 1993. New information on the systematics and postcranial skeleton of Herrerasaurus ischigualastensis (Theropoda: Herrerasauridae) from the Ischigualasto Formation (Upper Triassic) of Argentina. Journal of Vertebrate Paleontology 13 p. 400-423.
- S2CID 55723635.
- ^ S2CID 198274900.
- ^ PMID 21490016.
- ^ Mortimer, Mickey (2012). "Non-theropods".
- ^ Benedetto (1973). "Herrerasauridae, nueva familia de saurisquios triasicos". Ameghiniana. 10 (1): 89–102.
- ^ Galton, 1985. "The poposaurid thecodontian Teratosaurus suevicus v. Meyer, plus referred specimens mostly based on prosauropod dinosaurs, from the Middle Stubensandstein (Upper Triassic) of Nordwurttemberg". Stuttgart Beitrage zur Naturkunde (B). 116, 1-29.
- .
- ^ a b Novas, F.E. 1997. Herrerasauridae. In P.J. Currie and K. Padian (eds.). Encyclopedia of Dinosaurs. Academic Press.
- S2CID 128620874.
- PMID 21490016.
- ^ Alcober, O. A.; Martínez, R. N. (2010). "A new herrerasaurid (Dinosauria, Saurischia) from the Upper Triassic Ischigualasto Formation of northwestern Argentina". ZooKeys (63): 55–81.
- ^ H.-D. Sues. 1990. Staurikosaurus and Herrerasauridae. In D. B. Weishampel, H. Osmólska, and P. Dodson (eds.), The Dinosauria. University of California Press, Berkeley 143-147
- PMID 21594020.
- .
- ^ Alcober, Oscar A.; Martinez, Ricardo N. (2010). "A new herrerasaurid (Dinosauria, Saurischia) from the Upper Triassic Ischigualasto Formation of northwestern Argentina". ZooKeys (63): 55–81.
- hdl:11336/127498.
- .
- ^ J.F. Bonaparte, 1982, "Faunal Replacement in the Triassic of South America", Journal of Vertebrate Paleontology 2 (3): 362-371, December 1982.
- .
External links
- Media related to Staurikosaurus at Wikimedia Commons
- Data related to Staurikosaurus at Wikispecies
- Dinosaurs of Rio Grande do Sul