Talk:Spondylosoma

Characters found in Spondylosoma
Spondylosoma has these characters that are present in both dinosaurians and non-dinosaurians: elongate cervical vertebrae with ridgelike epipophyses, dorsal vertebrae with hyposphene-hypantrum auxiliary articulations, well-developed cranial, medial, and caudal chonoe, and ribs of the two main sacral vertebrae forming a U-shaped articulation to the ilium. Although Galton (2000) identified the ventrally bent condition of the sacral ribs as a rauisuchian affinity, Langer (2004) finds a number of synapomorphies aligning Spondylosoma with Dinosauria: sacral ribs facing laterally, horizontal condition of the dorsal margin of the sacral ribs, and ventral condition of the ventral margin of the sacral ribs, and deltopectoral crest present on the humerus. Because these affinities are more like dinosaurs than rausuchians, I'd say that Spondylosoma represents a dinosauriform closer to Dinosaria than to Marasuchus or Lewisuchus, if new remains of Spondylosoma are found. Time will decide the systematic status of Spondylosoma. 72.194.116.63 03:21, 8 March 2007 (UTC) Vahe Demirjian 19.19 7 March 2007

Affinities
In a recent Ph.D. dissertation by Nesbitt (2009) regarding the relationships of basal archosaurs, Spondylosoma is left at Archosauria incertae sedis because it lacks any characters that would place in either Pseudosuchia or Ornithodira. While the discovery of Nyasasaurus dampens the notion that dinosaurs did not diverge from their closest relatives in the mid-Triassic, in the case of Spondylosoma, there may be an as-yet-unknown clade of extinct archosaurs.

NESBITT, S.J.2009. The early evolution of archosaurs: rela-tionships and the origin of major clades [dissertation].New York: Columbia University. Available from: Pro-Quest Dissertations & Theses [online database]; http://www.proquest.com (publication number AAT 3374209). 68.4.28.33 (talk) 05:15, 15 December 2012 (UTC)Vahe Demirjian