New material of Parabrachyodus hyopotamoides from Samane Nala, Bugti Hills (Pakistan) and the origin of Merycopotamini (Mammalia: Hippopotamoidea)

Revision of the anthracothere Parabrachyodus hyopotamoides, endemic to the Lower Miocene of the Indian subcontinent and thus far confused with Brachyodus, is made possible by the description of unpublished specimens from the Samane Nala fossil-bearing deposits of the Bugti Hills (Pakistan). This is the first biochronologically constrained occurrence for a comprehensive series of this species. The analysis of cranial and dental morphological variations based on all known specimens of Parabrachyodus allows us to provide diagnostic characters for this monotypic genus. These include a four-crested upper molar protocone unique among artiodactyls and several convergences with subfamily Anthracotheriinae, like the two puzzling distal cristae on the last upper premolar protocone. A phylogenetic analysis at the hippopotamoid level, including Parabrachyodus and the enigmatic genera Telmatodon and Gonotelma (both also endemic to the Bugti Hills), is performed for the first time. These phylogenetically related taxa turn out to be basal to the tribe Merycopotamini, leading us to propose a more inclusive definition of the diagnosis of this tribe. Our results formally establish Elomeryx as the sister-group of Merycopotamini in Bothriodontinae, and definitely locate the early evolutionary history of Merycopotamini on the Indian subcontinent.

Read more…

Figure 4. Fragmentary cranium of Parabrachyodus hyopotamoides from Samane Nala 4 (UM-SAM4-001) in A, lateral view with an interpretative drawing. The grey full lines represent the sutures between bone units or the demarcation of teeth crowns, the grey dotted lines concern depressions on the skull surface. B, ventral view, displaying P1/-P2/ alveoli, and P3/-M3/. Scale bars equal 50 mm.

References

Gernelle K., Lihoreau F., Boisserie J.-R., Marivaux L., Métais G., Antoine P.-O. 2023 – New material of Parabrachyodus hyopotamoides from Samane Nala, Bugti Hills (Pakistan) and the origin of Merycopotamini (Mammalia: Hippopotamoidea) – Zoological Journal of the Linnean Society, XX, 1–32 – https://doi.org/10.1093/zoolinnean/zlac111