Epipophyses are bony projections of the

cervical vertebrae In tetrapods, cervical vertebrae (singular: vertebra) are the vertebrae of the neck, immediately below the skull. Truncal vertebrae (divided into thoracic and lumbar vertebrae in mammals) lie caudal (toward the tail) of cervical vertebrae. In ...

found in

archosauromorphs Archosauromorpha ( Greek for "ruling lizard forms") is a clade of diapsid reptiles containing all reptiles more closely related to archosaurs (such as crocodilians and dinosaurs, including birds) rather than lepidosaurs (such as tuataras, lizard ...

, particularly dinosaurs (including some basal birds). These paired processes sit above the postzygapophyses on the rear of the vertebral neural arch. Their morphology is variable and ranges from small, simple, hill-like elevations to large, complex, winglike projections. Epipophyses provided large attachment areas for several neck muscles; large epipophyses are therefore indicative of a strong neck musculature. The presence of epipophyses is a synapomorphy (distinguishing feature) of the group Dinosauria. Epipophyses were present in the basal-most dinosaurs, but absent in the closest relatives of the group, such as '' Marasuchus'' and ''

Silesaurus ''Silesaurus'' is a genus of silesaurid dinosauriform from the Late Triassic, of what is now Poland. Discovery Fossilized remains of ''Silesaurus'' have been found in the Keuper Claystone in Krasiejów near Opole, Silesia, Poland, which is al ...

''. They were typical for most dinosaur lineages; however, they became lost in several derived theropod lineages in the wake of an increasingly S-shaped curvature of the neck. Several scientific papers have observed that epipophyses were present in various non-dinosaur archosauromorphs. These include several pseudosuchians (''

Batrachotomus ''Batrachotomus'' is a genus of prehistoric archosaur. Fossils of this animal have been found in southern Germany and dated from the Ladinian stage of the Middle Triassic period, around 242 to 237 million years ago. ''Batrachotomus'' was descri ...

'', '' Revueltosaurus,

Xilousuchus ''Xilousuchus'' is an extinct genus of poposauroid from lower Triassic (Olenekian stage) deposits of Fugu County of northeastern Shanxi Province, China. It is known from the holotype, IVPP V 6026, a single well-preserved partial skele ...

, Effigia,

Hesperosuchus ''Hesperosuchus'' is an extinct genus of crocodylomorph reptile that contains a single species, ''Hesperosuchus agilis''. Remains of this pseudosuchian have been found in Late Triassic (Carnian) strata from Arizona and New Mexico.Colbert, E. H. 1 ...

''), basal avemetatarsalians ( aphanosaurs) non-archosaur

archosauriforms Archosauriformes (Greek for 'ruling lizards', and Latin for 'form') is a clade of diapsid reptiles that developed from archosauromorph ancestors some time in the Latest Permian (roughly 252 million years ago). It was defined by Jacques Gauthi ...

(''

Vancleavea ''Vancleavea'' is a genus of extinct, armoured, non- archosaurian archosauriforms from the Late Triassic of western North America. The type and only known species is ''V. campi'', named by Robert Long & Phillip A Murry in 1995. At that time, ...

'', ''

Halazhaisuchus ''Halazhaisuchus'' is an extinct genus of archosauriform from the Early Triassic of China. It is known from a single species, ''Halazhaisuchus qiaoensis'', which was named in 1982 from the lower Ermaying Formation in Shaanxi. It was assigned to ...

''), rhynchosaurs, several

tanystropheids Tanystropheidae is an extinct family of mostly marine archosauromorph reptiles that lived throughout the Triassic Period. They are characterized by their long, stiff necks formed from elongated cervical vertebrae with very long cervical ribs. So ...

, and

allokotosaurs Allokotosauria is a clade of early archosauromorph reptiles from the Middle Triassic, Middle to Late Triassic known from Asia, Africa, North America and Europe. Allokotosauria was first described and named when a new monophyletic grouping of spec ...

. Sauropod-oriented paleontologist Mike Taylor has informally suggested that epipophyses were also present in the vertebrae of certain pterosaurs.

References

{{cite book , editor=Philip J. Currie , editor2=Kevin Padian , first=Philip J. , last=Currie , chapter=Theropoda , title=Encyclopedia of dinosaurs , publisher=Acad. Press , isbn=978-0-12-226810-6 , year=1997, page=734 Dinosaur anatomy