Spondylosoma

Taxobox
name = "Spondylosoma"
fossil_range = Middle Triassic
regnum = Animalia
phylum = Chordata
classis = Sauropsida
superordo = ?Dinosauria
ordo = ?Saurischia
genus = "Spondylosoma"
genus_authority=von Huene, 1942
subdivision_ranks=Species
subdivision=
*"S. absconditum" von Huene, 1942 (type)

"Spondylosoma" (meaning "vertebra body") is a genus of archosaur of uncertain affinities from the late Ladinian-age Middle Triassic Lower Santa Maria Formation of Rio Grande do Sul Brazil. Recent studies have gone back and forth on its identity, suggesting rauisuchian or basal saurischian dinosaur. If it was a dinosaur, it would be the oldest.

History

Friedrich von Huene based the genus on a fragmentary postcranial skeleton 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, 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. [German] ]

With the discovery of basal dinosaur "Staurikosaurus", "Spondylosoma" drew attention as a possible relative. Authors have gone back and forth on the question, considering it either as a basal dinosaur, or as a "thecodont" or other basal archosaur. The two most recent papers to address it illustrate this clearly: in 2000, Peter Galton claimed that it lacks dinosaurian characteristics and was probably a rauisuchian,Galton, P.M. (2000). Are "Spondylosoma" and "Staurikosaurus" (Santa Maria Formation, Middle-Upper Triassic, Brasil) the oldest saurischian dinosaurs? "Palaontologische Zeitschrift" 74(3):393-423.] whereas in 2004 Max Langer disputed this and included "Spondylosoma" as a possible basal dinosaur similar to the herrerasaurs (but did not firmly rule out raisuchian 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. ISBN 0-520-24209-2] This debate will probably continue until better remains are found and described.

References