Monday 30 June 2014

Pareiasaurs from the Late Permian of Niger, West Africa.

The Pareiasaurs were a diverse and successful group of Parareptiles (an extinct group thought to have been essentially similar to Reptiles, but with no living descendants; all living Reptiles, Mammals and Birds are more closely related to one-another than any is to the Parareptiles) that appeared in the Middle Permian and flourished till the end of the Permian Period, but were wiped out by the End Permian Extinction Event. They are best known from Africa, particularly South Africa, from where nearly half of all described Pareiasaur species originate, but are also known from Zambia, Tanzania, Niger, Malawi and Morocco. Outside of Africa they are known from Brazil, China, Russia, Germany and Scotland.

The Pareiasaur Bunostegos akokanensis was described from a single skull, lacking lower jaws and eroded on the underside, from the Moradi Formation in the Agadez Department of northern Niger in 1888.

In a paper published in the Journal of Vertebrate Paleontology in July 2013, Linda Tsuji and Christian Sidor of the Burke Museum and Department of Biology at the University of Washington, Sébastion Steyer of the Bâtiment de Paléontologie at the Département Histoire de la Terre at the Muséum national d’Histoire naturelle, Roger Smith of Karoo Palaeontology at the Iziko South African Museum, Neil Tabor of the Roy M. Huffington Department of Earth Sciences at Southern Methodist University and Oumarou Ide of the Institut de Recherches en Sciences Humaines, Université de Niamey, describe a series of new specimens of Bunostegos akokanensis collected from the Moradi Formation in 2003 and 2006, and provide a revised description of the species based upon these.

The first new specimen described consists of an almost complete skull lacking its lower jaws, but accompanied by its right scapulocoracoid, and two dorsal vertebrae. The second new specimen comprises a three-dimensionally preserved skull with an eroded upper surface, and the third a braincase and part of the palate. Also described are isolated nasals, an interorbital skull roof, a right ulna, an isolated neural spine, and an isolated osteoderm.

The skull of Bunostegos akokanensis. Photograph and interpretative drawing in (A) dorsal and (B) ventral views. Abbreviations: bo, basioccipital; ec, ectopterygoid; f, frontal; j, jugal; l, lacrimal; m, maxilla; nb, nasal boss; p, parietal; pal, palatine; pf, postfrontal; pm, premaxilla; po, postorbital; pop, paroccipital process of opisthotic; pp, postparietal; ppf, prepalatal foramen; prf, prefrontal; pt, pterygoid; q, quadrate; qj, quadratojugal; sq, squamosal; st, supratemporal; st h, supratemporal ‘horn’; t, tabular; v, vomer. Tsuji et al. (2013).

The skull of Bunostegos akokanensis. Photograph and interpretative drawing in right lateral view. Abbreviations: j, jugal; l, lacrimal; m, maxilla; mf, anterior maxillary foramen; n, nasal; pf, postfrontal; pm, premaxilla; po, postorbital; prf, prefrontal; qj, quadratojugal; sq, squamosal; st, supratemporal. Tsuji et al. (2013).

Based upon this new material Bunostegos akokanensis is determined to be a medium-sized Pareiasaur with two or three dome-shaped bosses near the end of its snout, and horn-like structures above its eyes.

Reconstruction of the skull (A–C) and maxillary tooth (D) of Bunostegos akokanensis. Skull in (A) palatal, (B) dorsal, and (C) right lateral views. (D) tooth in labial view. Scale bar applies only to cranial reconstructions. Tsuji et al. (2013).

Restoration of a subadult Bunostegos akokanensis in life. Marc Boulay in Tsuji et al. (2013).

See also…

 Scavenging on the body of a Dicynodont Therapsid in the Late Permian of the Karoo Basin.

Therapsids were a group of Synapsid Amniotes...

 A Triassic Parareptile from South Africa.

The Parareptiles were a group of early Reptiles that flourished in the Permian. They were heavily depleted in the End Permian Extinction, but did survive into the Triassic. However they were never again a significant part of the fauna and disappeared before the start of the Jurassic, apparently unable to cope with competition from the emerging dinosaurs. The name...

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