Spinostropheus NT

''Spinostropheus'' is a genus of carnivorous neotheropod theropod dinosaur that lived in the Middle Jurassic period and has been found in the Tiouraren Formation, Niger. The type and only species is ''S. gautieri''.

History of discovery

In 1959, Albert-Félix de Lapparent excavated fossils near Oued Timmersöi, west of In Tedreft in the Agadez desert. Among the finds were the remains of a theropod. In 1960, de Lapparent, based on these, named a second species of the genus ''Elaphrosaurus'', ''E. gautieri''. The specific name honours François Gautier, the discoverer of the type locality.

In 2004, Paul Sereno, John Wilson and John Conrad named a separate genus: ''Spinostropheus''. The generic name is derived from Latin ''spina'', "spine", and Greek στροφεύς, ''stropheus'', "vertebra", and refers to the epipophyseal processes of the cervical vertebrae, which are prominent and dorso-ventrally flattened.

The holotype, MNHN 1961-28, was found in a layer of the Tiouraren Formation dating from the Bathonian- Oxfordian. De Lapparent had presumed that the strata dated from the Early Cretaceous. It consists of a cervical vertebra, seven pieces of the dorsals, three pieces of the sacrum, five tail vertebrae, a humerus, the lower end of a pubic bone, the lower end of a thighbone, a piece of a shinbone, a piece of a fibula, a metatarsal, four additional pieces of the metatarsus and a phalanx of a toe. The paratypes were an ulna, a metatarsal and a second partial skeleton consisting of vertebrae and limb elements. In 2004, Sereno et al. referred a third skeleton, specimen MNN TIG6 consisting of a series of cervical and dorsal vertebrae with some ribs. However, this specimen differs from ''Spinostropheus'' and likely belongs to a different noasaurid taxon. Other material referred to it includes cervical, dorsal, and caudal vertebra, partial left humerus, ulna, distal pubis, distal femur, incomplete tibia, fibulae, metatarsals, pedal phalangeal fragments, and manual unguals.

Description

''Spinostropheus'' was a relatively small theropod. In 2010, Gregory S. Paul estimated its length at 4 metres (13 feet), and its weight at 200 kg (441 lbs). In 2012 Thomas R. Holtz Jr gave a length of 6.2 meters (20.3 feet).

Classification

In 2002, a cladistic analysis by Sereno et al found ''Spinostropheus'' to be the sister taxon of the Abelisauria. In this study only the data from specimen MNN TIG6 were considered. Subsequent studies have recovered it as a basal ceratosaur based on the specimen MNN TIG6, outside of Neoceratosauria, more closely in the evolutionary tree to ''Elaphrosaurus''. According to Carrano et al. (2012), this taxon is a basal Tetanuran. Spinostro Rauhut and Carrano (2016) believe that the holotype and paratype specimens of ''Spinostropheus'' lack ceratosaurian features, unlike the specimen MNN TIG6 which they consider ceratosaurian, and suggest that ''Spinostropheus'' might be a basal tetanuran.

In their 2020 description of the abelisaurid '' Spectrovenator'', Zaher et al. recovered the ''Spinostropheus'' holotype as the sister taxon to the Averostra. The referred specimen, MNN TIG6, was found in a clade with ''Camarillasaurus'' as the basalmost noasaurids:

See also

* Timeline of ceratosaur research

References

{{Taxonbar, from=Q134710

Ceratosauria
Dinosaur genera
Middle Jurassic dinosaurs
Taxa named by Paul Sereno
Fossil taxa described in 2004
Dinosaurs of Niger