Spinostropheus

Spinostropheus is a genus of small carnivorous ceratosaurian 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.

Spinostropheus Temporal range: Middle Jurassic, Bathonian PreꞒ Ꞓ O S D C P T J K Pg N ↓
Life restoration of S. gautieri
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Dinosauria
Clade:	Saurischia
Clade:	Theropoda
Clade:	†Ceratosauria
Genus:	†Spinostropheus Sereno et al. 2004
Type species
†Spinostropheus gautieri Lapparent, 1960 (originally Elaphrosaurus 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.[1]

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.[2]

The holotype, MNHN 1961-28, was found in a layer of the Tiouraren Formation dating from the Bathonian-Oxfordian.[3] 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 e.a. referred a third skeleton, specimen MNN TIG6 consisting of a series of cervical and dorsal vertebrae together with some ribs.[2]

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).[4] In 2012 Thomas R. Holtz Jr gave a length of 6.2 meters (20.3 feet).[5] In 2016 Molina-Pérez & Larramendi gave a higher estimation of 8.5 meters (28 feet) and 600 kg (1.323 lbs) for the MNHN specimen known from an ulna.[6]

Phylogeny

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.[7] Subsequent studies have confirmed the original interpretation as a basal ceratosaur, outside of Neoceratosauria, more closely in the evolutionary tree to Elaphrosaurus.[8]

See also

• Timeline of ceratosaur research

References

1. A-F. de Lapparent, 1960, "Les Dinosauriens du "Continental intercalaire" du Saharal central", Mémoires de la Société géologique de France, nouvelle série 39(88A): 1-57
2. Sereno, P. C.; Wilson, J. A.; Conrad, J. L. (2004). "New dinosaurs link southern landmasses in the Mid-Cretaceous". Proceedings of the Royal Society B: Biological Sciences. 271 (1546): 1325–1330. doi:10.1098/rspb.2004.2692. PMC 1691741. PMID 15306329.
3. Rauhut, O.W.M.; Lopez-Arbarello, A. (2009). "Considerations on the age of the Tiouaren Formation (Iullemmeden Basin, Niger, Africa): Implications for Gondwanan Mesozoic terrestrial vertebrate faunas". Palaeogeography, Palaeoclimatology, Palaeoecology. 271: 259–267. doi:10.1016/j.palaeo.2008.10.019.
4. Paul, G.S., 2010, The Princeton Field Guide to Dinosaurs, Princeton University Press p. 78
5. Holtz Jr., Thomas R. (2012). "Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages" (PDF).
6. Molina-Pérez & Larramendi (2016). Récords y curiosidades de los dinosaurios Terópodos y otros dinosauromorfos. Barcelona, Spain: Larousse. p. 254. ISBN 9780565094973.
7. Sereno, P.C.; Conrad, J.L.; Wilson, J.A. (2002). "Abelisaurid theropods from Africa: Phylogenetic and biogeographic implications". Journal of Vertebrate Paleontology. 22 (3): 106A.
8. Carrano, M.; Sampson, S. (2008). "Phylogeny of Ceratosauria (Dinosauria: Theropoda)". Journal of Systematic Palaeontology. 6: 183–236. doi:10.1017/s1477201907002246.