New Apterodontinae (Hyaenodontida) from the Eocene Locality of Dur At-Talah (Libya): Systematic, Paleoecological and Phylogenetical Implications

Abstract

The African Hyaenodontida, mainly known from the Late Eocene and Early Oligocene Fayum depression in Egypt, show a very poor diversity in oldest Paleogene localities. Here we report new hyaenodontidans found in the late Middle Eocene deposits of Dur At-Talah (Central Libya), known to have recorded the earliest radiation of African anthropoids. The new hyaenodontidan remains are represented by dental and postcranial specimens comprising the historical material discovered by R.J.G. Savage in the last century and that of the recent Franco-Libyan campaigns. This material includes two apterodontines, in particular a subcomplete skeleton of Apterodon langebadreae nov. sp., bringing new postcranial elements to the fossil record of the genus Apterodon. Anatomical analysis of the postcranial remains of Dur At-Talah suggests a semi-aquatic lifestyle for Apterodon, a completely unusual locomotion pattern among hyaenodontidans. We also perform the first cladistic analysis of hyaenodontidans including apterodontines: Apterodon and Quasiapterodon appear close relatives to “hyainailourines”, in particular to the African Oligo-Miocene Metasinopa species. Apterodon langebadreae nov. sp. could be the most primitive species of the genus, confirming an African origin of the Apterodontinae and a further dispersion event to Europe before the early Oligocene. These data enhance our knowledge of early hyaenodontidan diversification into Africa and underline how crucial is the understanding of their evolutionary history for the improvement of Paleogene paleobiogeographic scenarii.

Craniodental and postcranial morphology ofIndohyaenodon raoifrom the early eocene of india, and its implications for ecology, phylogeny, and biogeography of hyaenodontid mammals

“…Several works have noted the likely paraphyly or polyphyly of Creodonta, and most of these have placed hyaenodontids in a monotypic order Hyaenodonta (Polly, 1994;Morlo et al, 2009Morlo et al, , 2014Groh e et al, 2012;Sol e, 2013;Sol e and Smith, 2013;Sol e et al, , 2014, which we follow here. Pending clearer resolution of the higher affinities of Hyaenodontidae, here we assign it temporarily to Eutheria, incertae sedis.…”

“…Relative to other groups of carnivorous eutherians with multiple carnassials (e.g., Oxyaenidae), hyaenodontids are most clearly distinguished by narrow, elongate skulls and by the retention of M3 and m3, at least in basal forms (Gunnell, 1998). Hyaenodontids are recorded from the late Paleocene to late Miocene of Holarctica and Africa (Rich, 1971;Ranga Rao, 1973;Lange-Badr e, 1979;Godinot, 1981;Godinot et al, 1987;Barry, 1988;Crochet, 1988;Gingerich, 1989;Gingerich and Deutsch, 1989;Kumar, 1992;Gunnell, 1998;Meng et al, taxonomic and character samples as well as from non-cladistic assessments of relationships (Barry, 1988;Polly, 1996;Egi et al, 2005;Peign e et al, 2007;Zack, 2011;Groh e et al, 2012;Sol e, 2013). The majority of early and middle Eocene hyaenodontids have traditionally been referred to Proviverrinae.…”

“…The majority of early and middle Eocene hyaenodontids have traditionally been referred to Proviverrinae. However, even given the conflicts just noted, there is broad agreement that this conventional conception of Proviverrinae is a paraphyletic stem assemblage including the most basal hyaenodontids (Polly, 1996;Egi et al, 2005;Peign e et al, 2007;Sol e et al, 2009;Zack, 2011;Groh e et al, 2012;Sol e, 2013), with other major hyaenodontid clades derived from a proviverrine ancestry. Based on a phylogenetic analysis of many of the earliest hyaenodontids, Sol e (2013) recently proposed restricting the Proviverrinae to an endemic radiation of European taxa that form a monophyletic clade that includes Proviverra.…”

Deciduous dentition and dental eruption of Hyainailouroidea (Hyaenodonta, “Creodonta,” Placentalia, Mammalia)

“…Apterodontines combine a key morphological feature of hypercarnivores, the reduction or absence of metaconids on the lower molars, with features of more generalist carnivores such as well-developed talonids on the lower molars, divergent metacones and paracones, and mesiodistally abbreviated metastyles on the upper molars (Van Valkenburgh, 2007) complicating dietary and phylogenetic inferences (Van Valen 1966;Szalay, 1967;Grohé et al, 2012). Recent phylogenetic studies (Borths et al, 2016;Borths and Seiffert, 2017) incorporate morphological features of the cranial vault , suggesting Apterodontinae as the sister clade of Hyainailourinae.…”

An ameghinornithid-like bird (Aves, Cariamae, ?Ameghinornithidae) from the early Oligocene of Egypt

“…The bulk of research on dispersal to and from Africa in the Paleogene has focused on mammals rather than birds, and the presence of an ameghinornithid-like bird in Africa provides new biogeographic data regarding distribution of birds along the Tethys Sea. Despite the much richer record of mammals from the Eocene and Oligocene of Asia, Europe, and Africa, there is no consistent biogeographic pattern clearly indicated as to dispersal among those continents (Holroyd and Maas, 1994;Grohé et al, 2012). However, the presence of related avian and mammalian taxa on both sides of the Tethys Sea (i.e., in Europe and North Africa), in addition to the occurrence of a potential ameghinornithid relative in the Paleocene of China (i.e., Q. rapax), indicates that dispersal did occur, even though the timing and directionality of those events cannot be constrained at present (Holroyd and Maas, 1994).…”