Thursday, 4 December 2014

A new species of Pig from the Late Miocene of Chad.


Pigs have been important parts of African faunas from the Miocene onwards, and have been extensively used to interpret environments and date strata. Unfortunately a large number of taxa have been erected from limited and fragmentary material, which has led to doubts about several interpretations of Miocene and Pliocene deposits that were initially based upon data from Pigs. The genus Nyanzachoerus was initially described in 1958 by Louis Leaky, and currently contains at least eleven species, though it is likely that this is an overestimation of true diversity, as many species were erected on very limited material.

In a paper published in the journal PLoS One on 27 August 2014,  Jean-Renaud Boisserie of the Institut de paléoprimatologie, Paléontologie Humaine: Évolution et Paléoenvironnements at the Université de Poitiers, Antoine Souron, also of the Institut de paléoprimatologie, Paléontologie Humaine: Évolution et Paléoenvironnements at the Université de Poitiers and of the Human Evolution Research Center at the University of California, Berkeley, Hassane Taïsso Mackaye and Andossa Likius of the Département de Paléontologie at the Université de N’Djamena, Patrick Vignaud, again of the Institut de paléoprimatologie, Paléontologie Humaine: Évolution et Paléoenvironnements at the Université de Poitiers and Michel Brunet, also of the Institut de paléoprimatologie, Paléontologie Humaine: Évolution et Paléoenvironnements at the Université de Poitiers and of the Collège deFrance, describe a new species of Nyanzachoerus from Toros-Ménalla, a fossil producing area in the northern Lake Chad basin, about 500 km northeast of N’Djamena.

The new species is named Nyanzachoerus khinzir, meaning ‘Pig’ in Chadian dialect Arabic. Boisserie et al. were cautious about erecting about erecting a new species of Nyanzachoerus, due to previous over-description of species within the genus, and because the site has previously been interpreted as being chronologically and environmentally similar to sites producing the widespread species Nyanzachoerus syrticus. However the site has now yielded a total of 280 specimens, including six well preserved crania (skulls), and this interpretation is no longer possible, due to its distinctive dentition.

Partial cranium of Nyanzachoerus khinzir.(A) Lateral view; (B) ventral view; (C) nuchal view; (D) occlusal view of left P3-M3. Scale bars equal 10 cm (A–C) and 5 cm (D). Boisserie et al. (2014).

The Toros-Ménalla locality has produced remains of Hippopotamuses, Elephants, Bovids, Anthracotheriids (explain), Birds, Carnivores and Fish as well as the Hominid Sahelanthropus tchadensis, currently the earliest known member of the group. Correlation of the fauna with that at other sites suggests that the Toros-Ménalladeposits are between 7.4 and 6.6 million years old, while attempts at radiocarbon-dating the Hominid producing localities here have yielded results of between 7.2 and 6.8 million years old and between 7.5 and 7.1 million years old.

Crania of Nyanzachoerus khinzir.(A–C)Male partial cranium in dorsal (A), lateral (B), and rostral (C) views; (D–E) ventral view of female partial cranium in ventral (D) and lateral (E) view; (F–G) male partial cranium in dorsal (F) and lateral (G) views; (H) rostral portion of palate ventral view. Scale bars equal 10 cm (A–G) and 5 cm (H). Boisserie et al. (2014).

An isotopic analysis of specimens of Nyanzachoerus khinzir suggests that had a mixed diet, but likely to include a considerable amount of grass, probably feeding largely in a wetland environment. Combined with previous data on fauna from the area, Boisserie et al. suggest that in the Late Miocene the Toros-Ménalla area may have been similar to the modern Okavango Delta in Botswana.

Mandibles of Nyanzachoerus khinzir.(A–C) male in dorsal (A), lateral (B), and occlusal view of right p2-m3 (C); (D–F) female mandible in dorsal (D), lateral (E), and occlusal view of right p2-m3 (F).Scale bars equal 10 cm (A–B, D–E) and 2 cm (C, F). Boisserie et al. (2014).

See also…

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