''Spondylosoma'' (meaning "vertebra body") is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

avemetatarsalia Avemetatarsalia (meaning "bird metatarsals") is a clade of diapsid Reptile, reptiles containing all archosaurs more closely related to birds than to crocodilians. The two most successful groups of avemetatarsalians were the dinosaurs and pterosau ...

archosaur Archosauria () or archosaurs () is a clade of diapsid sauropsid tetrapods, with birds and crocodilians being the only extant taxon, extant representatives. Although broadly classified as reptiles, which traditionally exclude birds, the cladistics ...

belonging to the clade

Aphanosauria Aphanosauria ("hidden lizards") is an extinct group of reptiles distantly related to dinosaurs (including birds). They are at the base of a group known as Avemetatarsalia, one of two main branches of archosaurs. The other main branch, Pseudosuchi ...

from the late

Ladinian The Ladinian is a stage and age in the Middle Triassic series or epoch. It spans the time between Ma and ~237 Ma (million years ago). The Ladinian was preceded by the Anisian and succeeded by the Carnian (part of the Upper or Late Triassic ...

-age

Middle Triassic In the geologic timescale, the Middle Triassic is the second of three epoch (geology), epochs of the Triassic period (geology), period or the middle of three series (stratigraphy), series in which the Triassic system (stratigraphy), system is di ...

Lower Santa Maria Formation in Paleorrota Geopark,

Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...

History

Friedrich von Huene Baron Friedrich Richard von Hoyningen-Huene (22 March 1875 – 4 April 1969) was a German nobleman paleontologist who described a large number of dinosaurs, more than anyone else in 20th-century Europe. He studied a range of Permo-Carbonife ...

based the genus on a fragmentary postcranial

skeleton A skeleton is the structural frame that supports the body of most animals. There are several types of skeletons, including the exoskeleton, which is a rigid outer shell that holds up an organism's shape; the endoskeleton, a rigid internal fra ...

held at the

University of Tübingen The University of Tübingen, officially the Eberhard Karl University of Tübingen (; ), is a public research university located in the city of Tübingen, Baden-Württemberg, Germany. The University of Tübingen is one of eleven German Excellenc ...

. This skeleton includes two

teeth A tooth (: teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, tear ...

, two cervical

vertebra Each vertebra (: vertebrae) is an irregular bone with a complex structure composed of bone and some hyaline cartilage, that make up the vertebral column or spine, of vertebrates. The proportions of the vertebrae differ according to their spina ...

e, four dorsal vertebrae, three sacral vertebrae,

scapula The scapula (: scapulae or scapulas), also known as the shoulder blade, is the bone that connects the humerus (upper arm bone) with the clavicle (collar bone). Like their connected bones, the scapulae are paired, with each scapula on either side ...

e, part of a

humerus The humerus (; : humeri) 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 (bone), radius and ulna, and consists of three sections. The humeral upper extrem ...

, part of a

femur The femur (; : femurs or femora ), or thigh bone is the only long bone, bone in the thigh — the region of the lower limb between the hip and the knee. In many quadrupeds, four-legged animals the femur is the upper bone of the hindleg. The Femo ...

, and part of a pubis. At the time, he thought it was a

prosauropod Sauropodomorpha ( ; from Greek, meaning "lizard-footed forms") is an extinct clade of long-necked, herbivorous, saurischian dinosaurs that includes the Sauropoda, sauropods and their ancestral relatives. Sauropods generally grew to very large siz ...

.von Huene, F. (1942). ''Die fossilen Reptilien des südamerikanischen Gondwanalandes.'' C.H. Beck:Munich, 342 p.

erman Erman may refer to: Given name * Erman Bulucu (born 1989), Turkish footballer * Erman Eltemur (born 1993), Turkish karateka * Erman Güraçar (born 1974), Turkish footballer * Erman Kılıç (born 1983), Turkish footballer * Erman Kunter (born ...

/ref>

With the discovery of the basal dinosaur ''

Staurikosaurus ''Staurikosaurus'' (Pronounced /ˌstɔɹ̠ikoʊˈsɔɹ̠ʌs/, '' STOR-ree-koh-SOR-ruhs''; "Southern Cross lizard") is a genus of herrerasaurid dinosaur from the Late Triassic of Brazil, found in the Santa Maria Formation. Description Colber ...

'', ''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 Thecodontia (meaning 'socket-teeth'), now considered an obsolete taxonomic grouping, was formerly used to describe a diverse "order" of early archosaurian reptiles that first appeared in the latest Permian period and flourished until the end of t ...

" or other basal archosaur. In 2000, Peter Galton noted that it lacks dinosaurian characteristics and was probably a

rauisuchia "Rauisuchia" is a paraphyletic group of mostly large and carnivorous Triassic archosaurs. Rauisuchians are a category of archosaurs within a larger group called Pseudosuchia, which encompasses all archosaurs more closely related to crocodilians ...

n more closely related to

rauisuchids Rauisuchidae is a group of large (up to ) predatory Triassic archosaurs. Some disagreement exists over which genera should be included in the Rauisuchidae and which should be in the related Prestosuchidae and Poposauridae, and indeed whether thes ...

,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 disputed this and included ''Spondylosoma'' as a possible basal dinosaur similar to the

herrerasaur Herrerasauridae is a family of carnivorous dinosaurs, possibly basal to either theropods or even all of saurischians, or even their own branching from Dracohors, separate from Dinosauria altogether. They are among the oldest known dinosaurs, ...

s (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 Sterling Nesbitt (born March 25, 1982, in Mesa, Arizona) is an American paleontologist best known for his work on the origin and early evolutionary patterns of archosaurs. He is currently an associate professor at Virginia Tech in the Departme ...

placed ''Spondylosoma'' at Archosauria ''

incertae sedis or is a term used for a taxonomy (biology), taxonomic group where its broader relationships are unknown or undefined. Alternatively, such groups are frequently referred to as "enigmatic taxa". In the system of open nomenclature, uncertainty ...

'', 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 Pseudosuchia, from Ancient Greek ψεύδος (''pseúdos)'', meaning "false", and σούχος (''soúkhos''), meaning "crocodile" is one of two major divisions of Archosauria, including living crocodilians and all archosaurs more closely relat ...

Ornithodira Avemetatarsalia (meaning "bird metatarsals") is a clade of diapsid reptiles containing all archosaurs more closely related to birds than to crocodilians. The two most successful groups of avemetatarsalians were the dinosaurs and pterosaurs. Di ...

. The redescription of '' Teleocrater'' 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.Nesbitt et al. 2017. The earliest bird-line archosaurs and the assembly of the dinosaur body plan. Nature.

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 Avemetatarsalia