Spinostropheus is a genus of small carnivorous ceratosaurian theropod dinosaur that lived in the Middle Jurassic period of Niger.
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 Elaphrosaurus: Elaphrosaurus 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]
Spinostropheus was a relatively small theropod. In 2010, Gregory S. Paul estimated its length at four metres, its weight at two hundred kilogrammes.[4]
In 2002, a cladistic analysis by Sereno et alii found Spinostropheus to be the sister taxon of the Abelisauria. In this study only the data from specimen MNN TIG6 were considered.[5] Subsequent studies have confirmed the original interpretation as a basal ceratosaur, outside of Neoceratosauria, more closely in the evolutionary tree to Elaphrosaurus.