Journal of Paleontology, 90(1), 2016, p. 170–181 Copyright © 2016, The Paleontological Society 0022-3360/16/0088-0906 doi: 10.1017/jpa.2016.13
A new anthracothere (Artiodactyla) from the early Oligocene, Fayum, Egypt, and the mystery of African ‘Rhagatherium’ solved
Afifi H. Sileem,1 Hesham M. Sallam,2 Abdel Galil A. Hewaidy,3 Ellen R. Miller,4 and Gregg F. Gunnell5
1Vertebrate Paleontology Section, Cairo Geological Museum, Cairo, Egypt ⟨
afifi.sileem@
yahoo.com⟩ 2Mansoura University Vertebrate Paleontology Center, Department of Geology, Mansoura University, Mansoura, 35516, Egypt ⟨
sallam@mans.edu.eg⟩
3Department of Geology, Faculty of Science, Al-Azhar University, Egypt ⟨
ahewaidy50@yahoo.com⟩ 4Department of Anthropology, Wake Forest University, Winston-Salem, North Carolina 27106, USA ⟨
millerer@wfu.edu⟩ 5Division of Fossil Primates, Duke Lemur Center, Durham, North Carolina 27705, USA ⟨
gregg.gunnell@
duke.edu⟩
Abstract.—Recent work on new anthracothere (Mammalia, Artiodactyla) specimens from the Jebel Qatrani Formation, early Oligocene, Fayum, Egypt, has revealed the presence of a new genus. Nabotherium new genus is described on the basis of a partial skull, several mandibular and maxillary specimens, and isolated teeth. The new genus exhibits a distinctive combination of features not seen in other Paleogene anthracotheres. The most noticeable characteristics of the new genus include the presence of large and well-developed upper and lower canines, caniniform third incisors, the presence of only a short diastema between the canine and first premolar, and broad, bunodont cheek teeth. This is in contrast to other contemporary anthracotheres, including other forms from the Fayum, which show a spatulate third incisor, a reduced canine, a much longer canine-premolar diastema, and more narrow, bunoselenodont cheek teeth. The presence of a relatively short rostrum with closely packed incisors, low-crowned and simple premolars, and low-crowned, bunodont molars indicates that members of the new genus would have been more efficient at crushing foods than slicing vegetation, and suggests a more varied herbivorous and frugivorous diet than was favored by other, more bunoselenodont Fayum anthracotheres.
Introduction
Fossiliferous sedimentary deposits in the Fayum Depression, Western Desert, Egypt (Fig. 1) have produced a remarkable assemblage of late Eocene and early Oligocene animals, repre- senting a wide variety of fish, amphibians, reptiles, birds, and mammals (e.g., Andrews, 1906; Rasmussen and Simons, 1988; Gingerich et al., 1990; Simons and Rasmussen, 1990; Domning and Gingerich, 1994; Domning et al., 1994; Seiffert et al., 2003, 2009; Seiffert, 2006, 2007, 2010, 2012; Simons et al., 2007; Sallam et al., 2009, 2011; Murray et al., 2010). Despite the fact that anthracotheres (Mammalia, Artiodactyla) are represented throughout most of the sequence (Fig. 2) and are among the most common faunal elements preserved in Fayum localities, very little has been published about the group since the early part of the twentieth century (Andrews, 1906; Schmidt, 1913; Ducrocq, 1997; Holroyd et al., 2010). At present, two anthracothere genera are known from the early Oligocene of the Fayum–Bothriogenys Schmidt, 1913 (four species) and Qatraniodon Ducrocq, 1997 (one species). Here we describe and discuss an additional new genus that replaces and enhances material previously included in the genus Rhagatherium Pictet, 1857. Among other distinguishing features, members of the new taxon are characterized by having a shorter snout, large canini- form canines, and more bunodont cheek teeth, suggesting a more frugivorous and varied diet than for the other, more bunoseledont, Fayum anthracotheres.
Materials and methods
Repositories and institutional abbreviations.—CGM = Cairo Geological Museum; DPC = Duke University Lemur Center, Division of Fossil Primates; NHM = The Natural History Museum, London.
Terminology.—Dental terminology follows that of Lihoreau and Ducrocq (2007). I, C, P, and M (for incisors, canines, pre- molars, and molars, respectively) are followed by superscript and subscript numbers, referring to upper and lower teeth, respectively. M2–3 and M3 of Nabotherium new genus with dental features labeled are illustrated in Figure 3.
Methods.—Ammonium chloride (NH4Cl)was used to whiten some of the specimens for the photographs presented
here.AnAF-S micro Nikkor 60-mm f/2.8G ED lens was used to photograph specimens. Stereophotographic figures are presented for some dentitions.
Systematic paleontology
Class Mammalia Linnaeus, 1758 Order Artiodactyla Owen, 1848
Family Anthracotheriidae Leidy, 1869 Subfamily Anthracotheriinae Leidy, 1869 Genus Nabotherium new genus Figures 4–8
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