Proc. Natl. Acad. Sci. USA Vol. 88, pp. 5267-5271, June 1991 Evolution Ancestral facial morphology of Old World higher primates (Anthropoidea/Catarrhini/Miocene/cranium/anatomy) BRENDA R. BENEFIT* AND MONTE L. MCCROSSINt *Department of Anthropology, Southern Illinois University, Carbondale, IL 62901; and tDepartment of Anthropology, University of California, Berkeley, CA 94720 Communicated by F. Clark Howell, March 11, 1991 ABSTRACT Fossil remains of the cercopithecoid Victoia- (1, 5, 6). Contrasting craniofacial configurations of cercopithe- pithecus recently recovered from middle Miocene deposits of cines and great apes are, in consequence, held to be indepen- Maboko Island (Kenya) provide evidence ofthe cranial anatomy dently derived with regard to the ancestral catarrhine condition of Old World monkeys prior to the evolutionary divergence of (1, 5, 6). This reconstruction has formed the basis of influential the extant subfamilies Colobinae and Cercopithecinae. Victoria- cladistic assessments ofthe phylogenetic relationships between pithecus shares a suite ofcraniofacial features with the Oligocene extant and extinct catarrhines (1, 2). catarrhine Aegyptopithecus and early Miocene hominoid Afro- Reconstructions of the ancestral catarrhine morphotype pithecus. AU three genera manifest supraorbital costae, anteri- are based on commonalities of subordinate morphotypes for orly convergent temporal lines, the absence of a postglabellar Cercopithecoidea and Hominoidea (1, 5, 6). Broadly distrib- fossa, a moderate to long snout, great facial height below the uted character states are interpreted as primitive and estab- orbits, a deep cheek region, and anteriorly tapering premaxilla. lish the polarity of morphoclines, with derived character The shared presence of these features in a catarrhine generally states having more restricted taxonomic distributions. Based ancestral to apes and Old World monkeys, an early ape, and an exclusively on living taxa, however, determination of mor- early Old World monkey indicates that they are primitive phocline polarities for cercopithecoid craniofacial attributes characteristics that typified the last common ancestor of Hom- is essentially arbitrary. Extant Old World monkeys are inoidea and Cercopithecoidea. These results contradict prevail- phylogenetically dichotomous, the Colobinae and Cercopith- ing cranial morphotype reconstructions for ancestral catar- ecinae being mutual sister groups characterized by contrast- rhines as Colobus- orHylobates-like, characterized by a globular ing facial configurations. Cercopithecine facial structure is anterior braincase and orthognathy. By resolving several equiv- distinguished from that ofthe relatively short-faced colobines ocal craniofacial morphocline polarities, these discoveries lay the by: a cranial vault of low height, narrow interorbital septum, foundation for a revised interpretation of the ancestral cranial long and narrow nasal bones, moderately long prognathic morphology of Catarrhini more consistent with neontological snout, deep zygoma, moderately tall infraorbital facial and existing paleontological evidence. height, and long anteriorly tapering premaxilla with relatively broad procumbent central incisors set anterior to lateral ones (7). Intrinsic evidence alone cannot reveal whether Colobinae The prevailing cranial morphotype reconstruction of the or Cercopithecinae is more likely to have retained the prim- common ancestor of Old World higher primates has had itive cercopithecoid condition. Craniofacial morphocline po- profound influences on interpretations of the phylogenetic larities within Hominoidea are generally equivocal due to relationships ofearly catarrhines (1, 2). Recent discoveries in their heterogeneity, the long-faced great apes contrasting northern and eastern Africa provide documentation of the with Hylobatidae in a manner similar to the cercopithecine/ craniofacial anatomy of Oligocene catarrhines generally an- colobine comparison.t Therefore, selection ofColobinae and cestral to apes and Old World monkeys and ofearly Miocene Hylobatidae as representative of primitive facial configura- apes (3, 4). Until this time, however, there has been an tions ofthe Cercopithecoidea and Hominoidea, respectively, absence of knowledge concerning the craniofacial configura- rests primarily upon the principle that similarities between tion of Old World monkeys from the earliest portion of their nonsister group taxa are likely to be conservative (1, 5, 6). evolutionary history. Recently discovered facial remains of The alternative explanation, that the orthognathy of Colobi- the earliest Old World monkey are described. Together with nae and Hylobatidae is homoplastic, has been dismissed due recently acquired knowledge of the anatomy of Oligocene to the perceived "remarkable similarity in cranial form catarrhines and early Miocene hominoids, these fossils en- among short-faced anthropoids" (2). able testing ofpreviously formulated craniofacial reconstruc- Cercopithecoid craniofacial morphocline polarities may be tions of the last common ancestor of Hominoidea and Cer- resolved, however, by reference to the fossil record. Unlike copithecoidea. Colobinae and Cercopithecinae, early-to-middle Miocene Current widely accepted reconstructions of ancestral catar- cercopithecoids from Africa constituting the archaic subfam- rhine craniofacial morphology are based on the premise that ily Victoriapithecinae (12) retain a crista obliqua on upper similarities shared by extant colobines and gibbons are conser- molars, a hypoconulid on first and second lower molars, and vative retentions from the ancestral Old World higher primate buccally rotated lower premolars from the ancestral catar- (1, 5, 6). The colobine/gibbon (and, by inference, ancestral rhine condition. Victoriapithecinae accordingly represent the catarrhine) craniofacial morphology is typified by: a cranial sister group to extant Old World monkeys (2, 13, 14). vault of moderate to great height with globular frontal squama, Resemblances between Victoriapithecinae and either extant broad interorbital septum, short and wide nasal bones, short Old World monkey subfamily are, therefore, most parsimo- orthognathous snout, shallow zygoma, short/moderate infraor- niously viewed as typifying the common ancestor of known bital facial height, and abbreviated premaxilla with relatively fossil and modern cercopithecoids. narrow vertically implanted upper incisors set equally forward tExceptions may be a primitively broad interorbital septum (5, 6) and The publication costs of this article were defrayed in part by page charge the conformation of the nasoalveolar clivus and incisive canal (8, 9) payment. This article must therefore be hereby marked "advertisement" although details of polarity for subnasal morphology in great apes in accordance with 18 U.S.C. §1734 solely to indicate this fact. and humans are disputed (10, 11). 5267 Downloaded by guest on September 25, 2021 5268 Evolution: Benefit and McCrossin Proc. Natl. Acad ScL USA 88 (1991) *.i. b., I 4.1 1.-,.-14,;q I A ... 4'. C D E FIG. 1. Facial remains of Victoria- pithecus. (A) Anterior facial reconstruc- tion based on specimens KNM-MB 19001 (frontal), 19689 (right zygomatic), and 18994 (left and right maxillae with P3-M3J (drawn by L. Tindimubona). (B) Lateral view of composite including specimens KNM-MB 19001, 19689, 18994, and 18993 (mandible with left and right I2-M3). (C) Anterior view offrontal (KNM-MB 19001). (D) Anterior view of right maxilla with P3-Ml (KNM-MB 18995). (E) Anterior view of left maxilla with P3-M3. l(Knm-MB 18994). (F) Lat- G eral view of left maxilla with PI-MI (KNM-MB 18994). (G) Palatal view of l I left and right maxillae with P3-M3. (KNM-MB 18994). DESCRIPTION AND COMPARISONS premaxilla, upper central incisor alveolae positioned anterior to those of the lateral incisors, broad upper central incisors Until recently, the craniofacial morphology of Victoriapith- with long roots relative to the lateral incisors, a narrow ecinae was ill known. Excavation ofmiddle Miocene deposits inferiorly V-shaped nasal aperture of moderate height, and a on Maboko Island in western Kenya from 1987 to 1989 led to deep cheek region relative to facial height (Table 1). the discovery of a frontal, zygomatic, mandible, maxillae, The frontal bone of Victoriapithecus (Fig. 1C) differs from and premaxillae of Victoriapithecus macinnesi (15). These the predicted ancestral Old World monkey morphotype in fossils provide the opportunity for an independent assess- having a narrow interorbital septum, with interorbital breadth ment, by outgroup comparison, of the morphocline polarity being only 13.3% of anterior biorbital breadth, like that of of colobine and cercopithecine craniofacial features. Recon- cercopithecine monkeys.$ The frontal is dominated by the struction of the ancestral cercopithecoid craniofacial mor- presence of distinct supraorbital costae (18) formed by coa- photype based on these discoveries can, in turn, be used to lescence of the anterolateral extents of the temporal lines address craniofacial morphotype reconstruction of the an- with the superciliary arches at the approximate midline of cestral eucatarrhine.§ each orbit, m. temporalis markings that converge relatively The facial morphology of Victoriapithecus (Fig. 1) differs anteriorly on the squamous portion, and absence of a pos- markedly in almost every respect from the Colobus-like face torbital depression behind glabella. These three features predicted for ancestral