Mesadactylus

Mesadactylus Temporal range: Late Jurassic
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Order:	†Pterosauria
Family:	†Anurognathidae
Genus:	†Mesadactylus Jensen & Padian, 1989
Species:	†M. ornithosphyos
Binomial name
Mesadactylus ornithosphyos Jensen & Padian, 1989

Mesadactylus ('mesa finger') is an extinct genus of pterosaur from the Kimmeridgian-Tithonian-age Upper Jurassic Morrison Formation of Colorado, USA.

The genus was named in 1989 by James Jensen and Kevin Padian. The type species is Mesadactylus ornithosphyos. The holotype is BYU 2024, a synsacrum of seven sacral vertebrae, featuring a for pterosaurs unique complete fusion of the spinae into a supraneural blade, a character, as the specific name indicates more typical for birds, at first leading Jensen to assign the fossil to a bird, Paleopteryx.

Further referred associated remains include arms bones, pectoral girdle bones, vertebrae (including cervix and sacral), and femorae.^[1] Additional material was described in 2004 (including a partial braincase)^[2] and 2006; in the latter publication, the authors suggested that its larger contemporary Kepodactylus could be the same animal, although there are minor differences.^[3][4]

Jensen and Padian classified Mesadactylus as a pterodactyloid. In 2007 S. Christopher Bennett claimed that the holotype and the referred material came from different forms and that, while the last was indeed of a pterodactyloid nature, the synsacrum belonged to a member of the Anurognathidae.^[5]

References

1. ^ Jensen, J. A., and Padian, K. (1989) Small pterosaurs and dinosaurs from the Uncompahgre fauna (Brushy Basin Member, Morrison Formation: ?Tithonian), late Jurassic, western Colorado. Journal of Paleontology 63:363–374.
2. ^ Smith, D.K., Sanders, R.K., and Stadtman, K.L. (2004). New material of Mesadactylus ornithosphyos, a primitive pterodactyloid pterosaur from the Upper Jurassic of Colorado. Journal of Vertebrate Paleontology 24(4):850-856.
3. ^ King, L.R., Foster, J.R., and Scheetz, R.D. (2006). New pterosaur specimens from the Morrison Formation and a summary of the Late Jurassic pterosaur record of the Rocky Mountain region. In: Foster, J.R., and Lucas, S.G. (eds.). Paleontology and Geology of the Upper Morrison Formation. New Mexico Museum of Natural History and Science Bulletin 36:149-161. ISSN 1524-4156.
4. ^ Harris, J.D., and Carpenter, K. (1996). A large pterodactyloid from the Morrison Formation (Late Jurassic) of Garden Park, Colorado. Neues Jahrbuch für Geologie und Paläontologie Monatshefte 1996(8):473-484.
5. ^ Bennett, S. C. (2007). "Reassessment of Utahdactylus from the Jurassic Morrison Formation of Utah". Journal of Vertebrate Paleontology 27(1): 257–260