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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Lower Miocene of the Indian subcontinent and thus far confused with Brachyodus , is made possible by the description of unpublished specimens from the Samane Nala fossil-bearing deposits of the Bugti Hills (Pakistan).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. [ABSTRACT FROM AUTHOR]

Teeth are frequently used in phylogeny in order to better characterize the evolution of extinct mammal species. While most studies have focused on the adult dentition, the consideration of characters from the deciduous dentition could also contribute to reinforce phylogenetic assumptions or disentangle phylogenetic issues. We chose to investigate the characters of the deciduous dentition in cetartiodactyl taxa in relation to the disputed relationships within hippopotamoids, especially the position of Hippopotamidae. We describe the deciduous dentition of 51 species, among a dataset of 70 cetartiodactyls. We noticed that second and third deciduous premolars have a much lower degree of molarization, and are more suitable for coding than fourth deciduous premolars. Thirty-nine resulting characters were thus added to a previously published matrix, and parsimony and maximum-likelihood analyses were performed. Both analyses provided a better resolved topology for most taxa than without these characters, and with better support for most nodes in the parsimony analysis. Moreover, this analysis provides additional characters supporting the hypothesis of an emergence of hippopotamids within bothriodontine anthracotheres from the Palaeogene of Africa. The promising use of characters from the deciduous dentition in phylogeny should allow discussion of the underlying ontogenetic mechanisms at the origin of dental homology. [ABSTRACT FROM AUTHOR]

Abstract: The status of the various species of Libycosaurus (Anthracotheriidae, Artiodactyla, Mammalia) has become extremely complicated following the initial identification of the type species as a dinosaur [Bonarelli, G., 1947. Dinosauro fossile del Sahara Cirenaico. Rivista di Biologia Coloniale, Roma 8, 23–33.]. The first reviser [Black, C., 1978. Anthracotheriidae, in: Maglio, V.J., Cooke, H.B.S. (Eds.), Evolution of African Mammals, Harvard University Press, Cambridge, pp. 423–434.] of the type species Libycosaurus petrocchii unknowingly switched the holotype which is small, for a much larger specimen, an error that passed unnoticed until the present study was undertaken. In his initial description of the type species, L. petrocchii, Bonarelli (1947) provided approximate measurements of the length and breadth of the type specimen from Sahabi, Libya, but these bear no relation to the reductions indicated in the figure captions, which suggest a much larger animal some 1.6 to 1.8 times bigger. In this paper the decision to accept the measurements rather than the figure captions is based on the writings of [Petrocchi, C., 1943. Il giacimento fossilifero di Sahabi. Collezione Scientifica e Documentaria a cura del Ministero dell’Africa Italiana 12, 1–167. Petrocchi, C., 1951. Notizie generali sul giacimento fossilifero di Sahabi. Storia degli Scavi - Risultati. Rendiconto delle Accademia Nazionale dei XL Roma, 1–33.] who discovered the snout and described it as being “di dimensioni più piccolo” (of much smaller dimensions) than another anthracothere skull found in the same general area at Sahabi which measured 70cm in total length. Until the holotype snout is relocated, some doubt must of course persist as to its precise status. Estimated dimensions of the teeth of the type specimen of L. petrocchii based on scaling Bonarelli''s figures to the measurements that he provided in the footnote on p. 26, indicate that it falls within the low end of the range of metric variation of Libycosaurus anisae (Black, 1972). Morphologically, L. petrocchii and L. anisae are similar, the supposed divergence between them being based on differences between the “false” type specimen from Sahabi mentioned by [Black, C., 1978. Anthracotheriidae, in: Maglio, V.J., Cooke, H.B.S. (Eds.), Evolution of African Mammals. Harvard University Press, Cambridge, pp. 423–434.] and the small specimens from Beglia, Tunisia. There are two other species of Libycosaurus in Libya, both of which are larger than L. petrocchii. The same two species occur in Chad. Libycosaurus increased in size throughout its known stratigraphic range (Faunal Sets P IV to P VII, ca. 14 to ca. 6Ma equivalent to MN 8 to MN 13) and as such it is potentially a useful biochronological indicator for deposits in which it occurs. The species L. petrocchii (and its synonym L. anisae) ranges in age from about 12 to 10Ma, the unnamed intermediate sized species ranges from ca. 10 to ca. 8Ma, and the very large species from ca. 8 to ca. 6Ma. This suggests that the Sahabi sedimentary succession spans about six million years and that the Toros–Ménalla deposits span about four million of geological time. [Copyright &y& Elsevier]