The cranium of Parapithecus grangeri, an Egyptian Oligocene anthropoidean primate Elwyn L. Simons* Department of Biological Anthropology and Anatomy, Duke University and Duke University Primate Center, 3705 Erwin Road, Durham, NC 27705-5000 Contributed by Elwyn L. Simons, January 2, 2001 A nearly complete skull of Parapithecus grangeri from the early Oligocene of Egypt is described. The specimen is relatively undis- torted and is undoubtedly the most complete higher primate skull yet found in the African Oligocene, which also makes it the most complete Oligocene primate cranium worldwide. Belonging in superfamily Parapithecoidea, a group regarded by some as the sister group to all other Anthropoidea, this skull reveals important information about the radiation of stem anthropoideans. This cranium is about 15% larger than size estimates based on a fragmentary cranium of its contemporary and close relative Apidium phiomense. It is about the same size as that of the gray gentle lemur, Hapalemur griseus, or of platyrrhines such as the owl monkey, Aotus trivirgatus, or the titi monkey, Callicebus torquatus. Comparatively small orbits and size differences in jaws and teeth show it was both diurnal and dimorphic. This is the only specimen of the species that shows (from sockets) that there were four small upper incisors. Several mandibular specimens of the species estab- lish that there were no permanent lower incisors and that the symphysis was fused. Like other early anthropoideans this species possessed a lower encephalization quotient and less-developed orbital frontality than later anthropoideans. There is full post- orbital closure and fusion of the metopic suture, and the ectotym- panic forms a rim to the auditory aperture. A probable frontal͞ alisphenoid contact is a potentially derived resemblance to Fig. 1. Relative cranial size of five species of Fayum Eocene and Oligocene Catarrhini. A proposed separate genus for the species P. grangeri primates, plotting orbital width against cranial length, and compared with a is not sustained. dwarf lemur, Cheirogaleus medius, and a slender loris, Loris tardigradus. ocene and Oligocene continental beds exposed in badlands species there are very few attributable postcranial bones from Elying north of Lake Qarun, Fayum Province, Egypt have which absolute size could be estimated. Because of the quality of produced a diverse vertebrate fauna as well as a broad series of preservation almost every detail of taxonomic or phyletic sig- fossil primates that include the world’s earliest undoubted and nificance about the cranium of Parapithecus can be determined well documented anthropoideans (see refs. 1 and 2 and refer- such as the arrangement, structure and dental formula of the ences therein). This specimen is of Oligocene age, being about upper teeth, shape of the premaxilla, location of the lacrimal 33 million years old (3). The skull was discovered in the central bone and foramen, extent of postorbital closure, exposure of the Ϸ part of Fayum Quarry I, a site that lies 200 m above the base frontal͞alisphenoid contact, size of the infraorbital and zygo- of the upper sequence of the Jebel Qatrani Formation, Fayum maticofacial (malar) foramina, metopic sutural closure, extent of Province, Egypt (4). This quarry was discovered in December the lateral pterygoid alae, proportions of the palate and nares, 1962 and has been collected from almost continuously since that and precise structure of the auditory region and basicranium. time until the present. But over this long period, during which Most of the details of cranial structure described here can be thousands of vertebrate fossils, including hundreds of primate seen more clearly than in almost all of the previously discovered maxillae and mandibles, were collected, no essentially complete skulls of Fayum primates. primate cranium was ever found there. The closest approxima- tion came in 1989 when a partial cranium of Apidium phiomense Systematics [Duke University Primate Center (DPC) 9867] was located in Order Primates Linnaeus, 1758: Suborder Anthropoidea Mivart, 1864; Quarry I. That specimen is dorsventrally crushed and lacks most Superfamily Parapithecoidea, Ka¨lin, 1961; Family Parapithecidae, of the basicranium and part of the facial region (5). In contrast, Schlosser, 1911. the cranial specimen described here, DPC 18651, is undistorted and has lost only the upper canines and two pairs of incisors Genus Parapithecus Schlosser, 1911. Emended generic diagnosis. (sockets only) and the left zygomatic arch. The specimen is Original descriptions of the genus and its distinctiveness were nearly unique in another respect in that it was almost completely based on the single individual lower dentition of the type enclosed in a rock-hard sandstone concretion that accounted for its relative lack of distortion. Abbreviations: CGM, Geological Museum, Cairo; YPM, Peabody Museum, Yale University; This cranium of Parapithecus is distinctly larger than well DPC, Duke University Primate Center; SNM, Stutgart Natural History Museum. preserved skulls of Fayum late Eocene Proteopithecus and *E-mail: [email protected]. Catopithecus, which are only about 70% as long as Parapithecus. The publication costs of this article were defrayed in part by page charge payment. This In turn, the length of this Parapithecus skull is only about 60% article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. that of the best-preserved Aegyptopithecus skull (Fig. 1). In this §1734 solely to indicate this fact. 7892–7897 ͉ PNAS ͉ July 3, 2001 ͉ vol. 98 ͉ no. 14 www.pnas.org͞cgi͞doi͞10.1073͞pnas.051003398 Downloaded by guest on September 25, 2021 specimen of the genus and species, Parapithecus fraasi. This maxillae DPC 2372 and 8793; attached parietal bones DPC 1098; specimen, Stutgart Natural History Museum (SNM) 12639a, a series of mandibular fragments particularly Peabody Museum, contained lower teeth in a partly preserved mandible that lacked Yale University (YPM) 21010; YPM 21019a, YPM 23796, YPM only the right P2, showed symphyseal fusion, and also showed a 26918;YPM 23953; YPM 23954; YPM 23973; DPC 1009; DPC unique feature among primates in that it appears to have lacked 1049; DPC 1053; DPC 1091; DPC 2376; DPC 2399; DPC 2807; adult lower incisors and had retained into young adulthood only DPC 2944;DPC 3110; DPC 3135; DPC 3876; DPC 3899; DPC a single pair of milk incisors. Almost every observation that 5263; DPC 5527; DPC 6326; DPC 6313; DPC 7252; DPC 8796; could or can be made about this specimen has been discussed and DPC 9857; DPC 10692; DPC 12303; DPC 13584; DPC 13589; challenged in a long series of papers (see refs. 5–14 and DPC 13590; DPC 14304; DPC 20580; numerous isolated teeth references therein). In the species to which the cranium de- and less complete YPM and DPC jaw fragments, and numerous scribed here belongs, Parapithecus grangeri, permanent lower specimens at the CGM including CGM 26918. incisors are lost, lower canines contact and wear against each other, and the mandibular symphysis is solidly fused. Dentally, Description and Comparison Parapithecus differs from Serapia in having P2 smaller, not larger Cranial Size and Braincase. DPC 18651 is the least distorted than P3. It is unlike Apidium in having premolars and molars that primate skull so far found in the Fayum Paleogene badlands and are less cuspidate, with relatively smaller hypocone and M3͞3as there seems to have been little dorsoventral compression of the well as showing the P2–4 central cusp comparatively smaller than braincase. The orbital margins have been somewhat deformed in the latter genus. Also unlike Apidium, where M1–3 distinctly but are clearly smaller relative to overall size than in skulls of the increase in size posteriorly, M1–3 of Parapithecus are subequal in South American monkey Callicebus torquatus. This cranium is Ͻ length or M3 M2. Parapithecus shows a shorter rostrum, and 65.8 mm long, which is similar to the skull length of Aotus comparatively smaller upper incisors (alveolae) as well as rela- trivirgatus or C. torquatus, whereas the occlusal area of the upper tively larger canines (both upper and lower) than Apidium.It premolars and molars of P. grangeri is clearly much greater and differs from Apidium in that the four main upper molar cusps are the brain volume distinctly smaller than in the latter two at the corners of a square, rather than having the hypocone much platyrrhines. The surface area of these upper teeth in Aotus is more lingually situated. Also, it differs from Qatrania in lacking approximately one-third and that of C. torquatus is 60% of that the large M1 trigonid that is open lingually. Qatrania has of P. grangeri. Kay and I (15) estimated the body weight of P. relatively larger hypoconulids that are closer to the entoconid. It grangeri as about 1,800 g (range 1632–1990). Such a body weight differs from Serapia in exhibiting almost no expression of the is more than twice the weight of these two monkeys and falls paraconid. P. grangeri has a comparatively larger zygomatic rather in the range of modern Cebus monkeys. Clearly, like foramen than does A. phiomense. In my view (see refs. 11 and 13) Aegyptopithecus, Parapithecus had a relatively much smaller brain no characters exist to validate a separate genus, Simonsius, used in relation to body size than does any living anthropoidean. by some authors (8, 14) for the species P. grangeri. Parapithecus is a medium-sized Fayum primate (Fig. 1). In Type species. P. fraasi. comparison, Proteopithecus has a skull length of about two-thirds Hypodigm. A single known specimen in the collection of the that of Parapithecus, DPC 18651, and it in turn is about 60% the SNM, SNM 12639a, is discussed but see below under species length of crania of Aegyptopithecus, see Fig. 1. distribution. I (5) figured and discussed facial (DPC 2385), frontal (DPC Species diagnosis. P. fraasi possesses larger and more bulbous 6641), and parietal (DPC 1098) fragments that I assigned to P.