''Spondylosoma'' (meaning "vertebra body") is a genus of avemetatarsalian

archosaur Archosauria () is a clade of diapsids, with birds and crocodilians as the only living representatives. Archosaurs are broadly classified as reptiles, in the cladistic sense of the term which includes birds. Extinct archosaurs include non-avian d ...

belonging to the clade Aphanosauria from the late Ladinian-age Middle Triassic Lower Santa Maria Formation in

Paleorrota Geopark The Paleorrota Geopark Project was established in Preparatory Procedure No. 1.29.008.000640/2017-22 done at the Public Prosecutor's Office (Brazil) of Santa Maria, Rio Grande do Sul. The geopark is composed of the Permian and Triassic The Triass ...

, Brazil.

History

Friedrich von Huene Friedrich von Huene, born Friedrich Richard von Hoinigen, (March 22, 1875 – April 4, 1969) was a German paleontologist who renamed more dinosaurs in the early 20th century than anyone else in Europe. He also made key contributions about v ...

based the genus on a fragmentary postcranial

skeleton A skeleton is the structural frame that supports the body of an animal. There are several types of skeletons, including the exoskeleton, which is the stable outer shell of an organism, the endoskeleton, which forms the support structure inside ...

held at the University of Tübingen. This skeleton includes two teeth, two cervical vertebrae, four dorsal vertebrae, three sacral vertebrae, scapulae, part of a

humerus The humerus (; ) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius and ulna, and consists of three sections. The humeral upper extremity consists of a roun ...

, part of a femur, and part of a pubis. At the time, he thought it was a prosauropod.von Huene, F. (1942). ''Die fossilen Reptilien des südamerikanischen Gondwanalandes.'' C.H. Beck:Munich, 342 p. erman/ref> Spondylosoma skeletal Headden

With the discovery of the basal dinosaur ''

Staurikosaurus ''Staurikosaurus'' (Pronounced "STORE-ee-koh-SAWR-us", "Southern Cross lizard") is a genus of herrerasaurid dinosaur from the Late Triassic of Brazil, found in the Santa Maria Formation. Description Colbert (1970) described ''Staurikosaurus' ...

'', ''Spondylosoma'' drew attention as a possible relative. Authors went back and forth on the question, considering it either as a basal dinosaur, or as a " thecodont" or other basal archosaur. In 2000, Peter Galton noted that it lacks dinosaurian characteristics and was probably a rauisuchian more closely related to rauisuchids,Galton, P.M. (2000). Are ''Spondylosoma'' and ''Staurikosaurus'' (Santa Maria Formation, Middle-Upper Triassic, Brasil) the oldest saurischian dinosaurs? ''Paläontologische Zeitschrift'' 74(3):393-423. whereas in 2004

Max Langer Max Langer (born 11 July 1897 in Spitzkunnersdorf ( Krs. Zittau); died 3 May 1985 in Niederoderwitz, was a German painter. From 1917 to 1921 he studied with in the Kunstgewerbeakademie Dresden. After a few years of wandering through Bavaria an ...

disputed this and included ''Spondylosoma'' as a possible basal dinosaur similar to the herrerasaurs (but did not firmly rule out rauisuchian affinities).Langer, M.C. (2004). Basal Saurischia. In: Weishampel, D.B., Dodson, P., and Osmólska, H. (eds.). ''The Dinosauria'' (second edition). University of California Press:Berkeley, 25-46. In his 2009 thesis on archosaur evolution, Sterling Nesbitt placed Spondylosoma at Archosauria '' incertae sedis'', noting that the characters used by Galton to tentatively place the genus in Rauisuchidae are also found in Aetosauria, and that the holotype lacks characters to place it in either Pseudosuchia or Ornithodira. The redescription of ''

Teleocrater ''Teleocrater'' (meaning "completed basin", in reference to its closed acetabulum) is a genus of avemetatarsalian archosaur from the Middle Triassic Manda Formation of Tanzania. The name was coined by English paleontologist Alan Charig in his ...

''Nesbitt et al. 2017. The earliest bird-line archosaurs and the assembly of the dinosaur body plan. Nature. revealed numerous similarities between ''Spondylosoma'' and a few other Triassic taxa leading to their referral to a new clade of archosaurs, Aphanosauria, which is the sister to Ornithodira within Avemetatarsalia.

References

{{Taxonbar, from=Q549748 Middle Triassic archosaurs Middle Triassic reptiles of South America Ladinian genera Triassic Brazil Fossils of Brazil Santa Maria Formation Paleontology in Rio Grande do Sul Fossil taxa described in 1942 Prehistoric avemetatarsalians