Wits Evolutionary Studies Institute (ESI)

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Author: search.filters.author.Geraads, Denis

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    Hipparion pomeli sp. nov from the late Pliocene of Ahl al Oughlam, Morocco, and a revision of the relationships of Pliocene and Pleistocene African hipparions
    (BERNARD PRICE INSTITUTE FOR PALAEONTOLOGICAL RESEARCH, 2007) Eisenmann, Vera; Geraads, Denis
    This paper addresses three points: 1) the description of a new species (H. pomeli sp. nov.) of Late Pliocene hipparion from Morocco; 2) preliminary notes on hipparion skulls from Langebaanweg E Quarry (H. hendeyi sp. nov.) and Chad Kossoum Bougoudi; 3) a new interpretation of African hipparion relationships. The Appendix presents practical techniques allowing the estimation of adult dimensions in juvenile skulls and correlations between two mandibular and skull dimensions. H. pomeli was a medium-sized species related to, but smaller than, H. hasumense from East Africa. The distance vomer–basion was small and there was no reduction of the third incisors. The lower cheek teeth were caballine, moderately hypsodont, with moderate ectostylids. The limb proportions were cursorial. H. pomeli differed from the true ‘Eurygnathohippus’ (H. afarense and H. cornelianum) by the basi-cranial proportions and the lack of reduction of the third incisors. H. hendeyi had an extremely short vomer–basion distance, a short distance between the orbit and the POF, primitive teeth, and slender limb bones. It cannot be derived from H. africanum or from H. turkanense. The greatest resemblances are with (the much smaller) H. moldavicum of Taraklia and H. giganteum of Grebeniki. The tentative reconstruction of H. feibeli’s skull indicates a possible relationship with H. hendeyi. The very large skull from Kossoum Bougoudi, Chad, resembles, but is much larger than, the Chinese H. dermatorhinum; its dimensions are compatible with the European H. crassum and the Mongolian H. tchicoicum. It is proposed that more than two migrations gave rise to the various African species of hipparions.
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    New skulls of Kolpochoerus phacochoeroides (Suidae: Mammalia) from the late Pliocene of Ahl al Oughlam, Morocco
    (BERNARD PRICE INSTITUTE FOR PALAEONTOLOGICAL RESEARCH, 2004) Geraads, Denis
    The discovery of two male skulls of Kolpochoerus phacochoeroides from the late Pliocene of Ahl al Oughlam in Morocco, and the revision of the whole collection from this locality, allows us to extend the description of this North African form, to estimate its sexual dimorphism and the extent of individual variation in a large isochronous sample, to reveal some ontogenic changes, and to confirm its distinction as a species on its own, as its cranial proportions (large occipital, short snout) and tooth characters (lack of enamel on upper canines, reduced incisors and premolars, complicated third molars) set it clearly apart from the East and South African forms. A cladistic analysis shows that K. phacochoeroides and Hylochoerus are the terminal branches of the Kolpochoerus clade, which is the sister-group of Potamochoerus.
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    Middle Pliocene Bovidae from Hominid-bearing sites in the Woranso-Mille area, Afar region, Ethiopia
    (Bernard Price Institute for Palaeontological Research, University of the Witwatersrand, 2009-12) Geraads, Denis; Melillo, Stephanie; Haile-Selassie, Yohannes
    Hominid-bearing sites of the northwestern part of the Woranso-Mille research area, dated to between 3.7 and 3.8 Mya, yield 10 species of Bovidae. The evolutionary stages of the most common species fit quite well this radiometric age. The most abundant bovid is a new species of Aepyceros, of large size, with upright, lyrated horn-cores; it is clearly distinct from the impalas of younger sites in the same area, and from those sampled at Hadar. A new species of Tragelaphus is also common; its horn-cores exhibit reduced anterior keel and antero-posterior compression foreshadowing the most common form at Hadar. A single partial Ugandax skull, despite some primitiveness, may fit into the variation range of U. coryndonae from Hadar. Other tribes are rare; the virtual absence of reduncines is a major difference from younger sites, but the occurrence of a cephalophine and of Neotragus is worth noting. This assemblage unambiguously indicates an environment with a significant component of arboreal vegetation.
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    New skulls of Kolpochoerus phacochoeroides (Suidae: Mammalia) from the late Pliocene of Ahl al Oughlam, Morocco
    (Bernard Price Institute for Palaeontological Research, 2004-12) Geraads, Denis
    The discovery of two male skulls of Kolpochoerus phacochoeroides from the late Pliocene of Ahl al Oughlam in Morocco, and the revision of the whole collection from this locality, allows us to extend the description of this North African form, to estimate its sexual dimorphism and the extent of individual variation in a large isochronous sample, to reveal some ontogenic changes, and to confirmits distinction as a species on its own, as its cranial proportions (large occipital, short snout) and tooth characters (lack of enamel on upper canines, reduced incisors and premolars, complicated third molars) set it clearly apart from the East and SouthAfrican forms.Acladistic analysis shows that K. phacochoeroides and Hylochoerus are the terminal branches of the Kolpochoerus clade, which is the sister-group of Potamochoerus.
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    A new caprin bovid (Mammalia) from the late Miocene of Morocco
    (2012-12) Geraads, Denis; El Boughabi, Siham; Zouhri, Samir
    We describe here a bovid skull from the Upper Member of the Aït Kandoula Formation near Ouarzazate, Morocco, which can be dated by biostratigraphy to the late Miocene, Turolian-equivalent.We assign it to a new taxon, Skouraia helicoides, gen. nov., sp. nov. It has long horn-cores that are much inclined backwards, strongly spiralled in homonymous direction, very divergent, and have a strong anterolateral keel. The strong cranial flexure, broad basioccipital, and aegodont teeth demand inclusion of this new taxon within the tribe Caprini, a mostly Eurasian group with few African representatives. Skouraia must be an early offshoot of this tribe, but its highly derived cranial features suggest that the Caprini may have experienced, in the poorly known late Miocene of Africa, a broader morphological diversification than in Europe.