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ANTHROPOLOGY
Anthropoid primates from the Oligocene of Pakistan (Bugti Hills): Data on early anthropoid evolution and biogeography







*Laboratoire de Paléontologie, Institut des Sciences de l'Évolution de Montpellier, Unité Mixte de RechercheCentre National de la Recherche Scientifique 5554, c.c. 064, Université Montpellier II, Place Eugène Bataillon, F-34095 Montpellier Cedex 05, France;
Laboratoire des Mécanismes de Transfert en Géologie, Institut des Sciences de la Terre, 14 Avenue Édouard Belin, F-31400 Toulouse, France;
Earth Sciences Division, Pakistan Museum of Natural History, Garden Avenue, Shakarparian, 44000 Islamabad, Pakistan; ¶Laboratorio de Paleomagnetismo, Instituto de Geofisica, Universidad Nacional Autonoma de Mexico, 04510 Mexico Distrito Federale, Mexico; ||Paleontology Section, Bureau of Geological Survey, Department of Mineral Resources, Rama VI Road, 10400 Bangkok, Thailand; **Département Histoire de la Terre, Unité Mixte de RechercheCentre National de la Recherche Scientifique 8569, Muséum National d'Histoire Naturelle, 8 Rue Buffon, F-75231 Paris Cedex 05, France; and 
Section of Vertebrate Paleontology, Carnegie Museum of Natural History, 4400 Forbes Avenue, Pittsburgh, PA 15213
Communicated by F. Clark Howell, University of California, Berkeley, CA, April 27, 2005 (received for review February 8, 2005)
| Abstract |
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phylogeny | Paleogene | South Asia
| Systematic Paleontology |
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Bugtipithecus, Gen. Nov. Type species. Bugtipithecus inexpectans sp. nov.
Etymology. The genus name refers to the Bugti tribe (Greek pithekos, apes).
Diagnosis. As for the type species.
Bugtipithecus inexpectans Sp. Nov. Etymology. Epithet in reference to the unexpected occurrence of higher primates in the Oligocene of South Asia.
Holotype. UMC-DBC 2174, right M1 (Fig. 2J), temporarily housed in the Palaeontology Department, University of Montpellier.
Horizon and locality. Bugti Member, Lower Chitarwata Formation (early Oligocene), Paali Nala DBC2, Bugti Hills (Balochistan, Pakistan; Fig. 1).
Diagnosis. Small-bodied amphipithecid, similar in size to the modern mouse lemur Mirza coquereli. Differs from Myanmarpithecus, Siamopithecus, and Pondaungia (including "Amphipithecus") (7) in having cusps less inflated and more marginally positioned, upper molars with a relatively high degree of "waisting" lingual to the metacone, a stronger hypoparacrista, a complete lingual cingulum, lower molars showing a massive but deeply notched lingual talonid wall (strong postmetacristid and preentocristid), a smaller and more lingually positioned M3 heel, and in lacking enamel wrinkles on the occlusal surfaces of both upper and lower teeth. Body-mass estimate of 350 g is based on M1 area (from all primate least-squares regression equation) (22). For hypodigm, description, and metrics, see supporting information, which is published on the PNAS web site.
Comparisons. The Amphipithecidae are generally known to be large-bodied [69 kg (Pondaungia and Siamopithecus)] or medium-sized [12 kg (Myanmarpithecus)] primates, having upper and lower cheek teeth strongly bunodont with moderately to highly crenulated enamel surfaces. Bugtipithecus gen. nov. contrasts with the classic amphipithecid condition in being much smaller and in having teeth with more acute cusps and smooth enamel surfaces. Although differing in these respects, Bugtipithecus also exhibits a set of features otherwise found only in the Amphipithecidae. For instance, as in Pondaungia, Siamopithecus, and Myanmarpithecus, M12 in Bugtipithecus exhibit a relatively well developed hypocone on the distolingual cingulum that is united with the protocone (via the postprotocrista) by a strong prehypocrista. In Bugtipithecus, the postprotocrista is not as buccally restricted as it is in Siamopithecus. Rather, it extends distobuccally, as it does in a number of other Paleogene taxa customarily regarded as Anthropoidea (Eosimiidae, Proteopithecidae, Oligopithecidae, and Propliopithecidae) and also, but to a lesser degree, in some omomyiform (e.g., Omomys) and adapiform (e.g., sivaladapids) lineages. In contrast to Siamopithecus, Myanmarpithecus and Pondaungia have small conules on their upper molars. The M12 of Bugtipithecus have a distinct metaconule but differ from those of Myanmarpithecus and Pondaungia in lacking the paraconule. The presence of well developed conules on the upper molars is a fairly widespread condition in omomyiforms and also in some adapiforms. In contrast, most of the early anthropoid lineages have reduced [Eosimiidae (Eosimias and Phenacopithecus), and Proteopithecidae] or absent [Eosimiidae (Bahinia), Oligopithecidae, and Propliopithecidae] conules, although exceptions to this generalization are found among parapithecids (e.g., Parapithecus and Apidium) and Algeripithecus (23), which resemble amphipithecids (Pondaungia and Myanmarpithecus) in bearing well developed conules. In Bugtipithecus, the metaconule is connected lingually to the postprotocrista (and not to the "hypometaconule crista" as in omomyiforms and adapiforms) and buccally to a very short crest, which is probably homologous with the hypometacrista found in Siamopithecus and in many stem and crown anthropoids (e.g., Bahinia, Eosimias, Phenacopithecus, Catopithecus, Oligopithecus, Moeripithecus, Aegyptopithecus, pliopithecoids, and platyrrhines). Mesial and parallel to this short hypometacrista, upper molars of Bugtipithecus display an oblique hypoparacrista (distinct from the postparaconule crista occurring in most omomyiforms and some adapiforms), which is a character observable in many anthropoids (except Proteopithecus) but with different degrees of development (i.e., lower, thinner, or shorter). In Bugtipithecus, the hypoparacrista is long, strong, and elevated, as in Siamopithecus and Bahinia. In most species of early primates, the preprotocrista connects to the paraconule or terminates midway between the paracone and protocone if the paraconule is absent. The preparaconule crista generally represents a buccal extension of the preprotocrista and usually connects to a small parastyle. Upper molars of Bugtipithecus, as well as those of Pondaungia, exhibit a condition unusual among early primates in lacking the preparaconule crista. The anterior cingulum is therefore not interrupted, as it is in most primate species, extending continuously from the protocone to the parastyle. Upper molars in Bugtipithecus bear a strong and continuous lingual cingulum, as in early anthropoids (except Parapithecus and Siamopithecus, which show considerable lingual inflation of the protocone). This aspect of the lingual cingulum differs from the condition found in many omomyiforms and adapiforms, in which this cingulum is not continuous but broken lingual to the protocone. As in propliopithecids (Propliopithecus, Moeripithecus, and Aegyptopithecus) and all other amphipithecids, the M12 in Bugtipithecus have a cuspate hypocone. This character is not as well developed in oligopithecids (especially Oligopithecus) and proteopithecids, in which a small enamel swelling occurs on a distolingual expansion of the lingual cingulum (Catopithecus and Proteopithecus). Eosimiids have a similar distolingual expansion of the M12 talon region but have no hypocone.
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Family Eosimiidae. Beard et al., 1994.
Phileosimias Gen. Nov. Type species. Phileosimias kamali sp. nov.
Included species. Phileosimias brahuiorum sp. nov.
Etymology. The name means "the ally of Eosimias" (Greek philios, ally).
Diagnosis. Eosimiid of the size of Phenacopithecus. Upper molars differ from those of Eosimias, Phenacopithecus, and Bahinia in having cuspate conules, weaker development of lingual and buccal cingula, less waisting distolingual to the metacone (particularly evident in Eosimias and Phenacopithecus), and in lacking both hypoparacrista and hypometacrista. Lower molars have the hypoconulid located slightly more lingual to the midline than in other eosimiids, and the P4 has no mesiolingual cingulid.
Phileosimias kamali Sp. Nov. Etymology. The species name is in honor of our intrepid friend Kamal Madjidulah (Director of The Star, Karachi, Pakistan), in recognition of his high efficiency in organizing the French paleontological missions in the Bugti Hills and his efforts toward promoting cultural knowledge in Pakistan. Holotype. UMC-DBC 2199, right M1 (Fig. 3F), temporarily housed in the Palaeontology Department, University of Montpellier.
Horizon and locality. Bugti Member, Lower Chitarwata Formation (early Oligocene), Paali Nala DBC2, Bugti Hills (Balochistan, Pakistan; Fig. 1).
Diagnosis. Differs from Phileosimias brahuiorum sp. nov. in being slightly larger, in showing more triangular and distally waisted upper molars, a buccal expansion of the metacone, no hypocone, a massive and lingually inflated protocone, the metacone of M3 distal to the paracone, and in having less extensive lingual and buccal cingula. Body-mass estimate of 250 g, based on M1 area (22). For hypodigm, description, and metrics, see supporting information.
Phileosimias brahuiorum Sp. Nov. Etymology. The name derives from "Brahui," the second Baloch language, in homage to all speakers of this language.
Holotype. UMC-DBC 2221, right M2 (Fig. 3I), temporarily housed in the Palaeontology Department, University of Montpellier.
Horizon and locality. As for Phileosimias kamali sp. nov.
Diagnosis. Differs from Phileosimias kamali sp. nov. in having upper molars with more rectangular and transverse outline (not distally waisted), better development of buccal and lingual cingula, the presence of a minute but distinct hypocone, a slender protocone, no buccal expansion of the metacone, and in showing the metacone of M3 distally more lingual with respect to the paracone. For hypodigm, description, and metrics, see supporting information.
Comparisons. At first glance, when considering upper molars only, Phileosimias may appear morphologically divergent with respect to other eosimiids (Eosimias, Bahinia, and Phenacopithecus). Indeed, the presence of cuspate conules, weaker development of the buccal and lingual cingula (especially in Phileosimias kamali), and the absence of both hypoparacrista and hypometacrista differ from the typical eosimiid dental pattern and could even better match that of omomyiforms (notably Omomys). Eosimiids generally exhibit an important distolingual expansion of the lingual cingulum (talon region), have a moderately (Eosimias and Phenacopithecus) to strongly (Bahinia) developed buccal cingulum, and show minute (Eosimias and Phenacopithecus) to indistinct (Bahinia) conules. However, the weak development of buccal and lingual cingula on the upper molars of Phileosimias is not uniform within the genus because a couple of specimens attributed to Phileosimias brahuiorum show well developed cingula. As in all eosimiids and more generally in early anthropoids (oligopithecids, proteopithecids, parapithecids, propliopithecids, and amphipithecids), both species of Phileosimias have upper molars without metaconule cristae (pre-, post-, and hypo-) and postparaconule crista, and lack even rudimentary development of a postprotocingulum (Nannopithex fold), common characters in adapiforms and omomyiforms (except Omomys). Upper molars of Phileosimias show, in contrast, well developed and buccally oriented pre- and postprotocristae (U-shaped protocone), which connect the paraconule and the metaconule, respectively. These teeth also exhibit a buccal expansion of their stylar regions (parastyle and metastyle), a feature that is particularly well developed in eosimiids, but which also occurs in some omomyiforms, such as Macrotarsius, Shoshonius, and Altiatlasius.
The morphology of the lower molars of Phileosimias does not depart significantly from that of other eosimiid primates. The main anatomical difference is the position of the hypoconulid, which is lingual to midline in Phileosimias and not centrally located, as in Phenacopithecus, or slightly buccal to midline, as in Eosimias and those omomyiforms that have a hypoconulid. The location of this distal cuspid in Phileosimias recalls the condition that occurs in early anthropoids from North Africa (Catopithecus, Oligopithecus, Proteopithecus, Serapia, and Arsinoea) and sivaladapid adapiforms from Asia (e.g., Hoanghonius and Guangxilemur), in which the hypoconulid is more lingual and frequently twinned with the entoconid. In Phileosimias, as in all anthropoids, the cristid obliqua on M1 is invariably lateral and reaches the base of the trigonid wall at a point distal to the protoconid rather than distolingual to the protoconid or to the metaconid, as in omomyiforms and adapiforms. Lower molars in Phileosimias, as in all other eosimiids, have trigonids that are open lingually and possess a strongly cuspidate paraconid. Except for M1, on which the paraconid is commonly reduced in early anthropoids (notably Proteopithecus, Serapia, Arsinoea, Catopithecus, and Oligopithecus), the paraconid is generally absent on M13 and the trigonid is closed lingually in anthropoids (propliopithecids, parapithecids, amphipithecids, pliopithecoids, and platyrrhines). The presence of a paraconid on all lower molars is observed in omomyiforms and tarsiids. In eosimiids, the paraconid on M23 is, however, widely spaced from the metaconid and sometimes mesiolingually positioned between the protoconid and the metaconid (in Phenacopithecus and Phileosimias), whereas it is generally mesial and twinned to the metaconid in omomyiforms.
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| Discussion and Conclusions |
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31 million years ago was, indeed,
14° farther south than in recent times (29°N) because of the northward drift of the Indian Plate (35).
The results of our various phylogenetic analyses (Fig. 4), primarily based on morphological characters (see supporting information), consistently point toward the monophyly of a large clade, including Asian Eosimiidae, Amphipithecidae, AraboAfrican Oligopithecidae, Propliopithecidae, African Proteopithecidae, Parapithecidae, and South American platyrrhine primates. Assuming this clade to be the Anthropoidea clade (10), from the present evidence, eosimiids and amphipithecids (and by extension Phileosimias and Bugtipithecus, respectively) are stem anthropoids (17) and, as such, support the hypothesis that Asia was the ancestral homeland of the Anthropoidea clade (16, 10). The discovery of Phileosimias and Bugtipithecus from the Oligocene of Pakistan demonstrates that eosimiids remained highly evolutionary conservative through time and that amphipithecids were very autapomorphic with respect to their coeval African relatives, which had evolved into advanced species with more or less modern anatomy (19, 3638). This apparent evolutionary disparity between EoceneOligocene anthropoids of Asia and Africa suggests that anthropoids must have dispersed rapidly between the two continents (39) just after their common Asian ancestry and evolved in relative isolation on both continents during the Paleogene. The cooccurrence of eosimiids and amphipithecids in Pakistan extends considerably the paleogeographic distribution of both families, which were apparently restricted to Southeast Asia during the Eocene. Their fossil record is still scarce but is now sufficient for demonstrating that anthropoids were a diverse and successful group in South Asia during the Paleogene. A simple examination of body weights of the well known Eocene forms (predicted from the M1 area) (22) reveals a large spectrum of body sizes (17), ranging from very tiny species [100400 g (Eosimias, Phenacopithecus, and Bahinia)] to much larger-bodied forms [12 kg (Myanmarpithecus) and 69 kg (Pondaungia and Siamopithecus)]. Bugtipithecus and Phileosimias document an unsuspected and more recent phase of the evolutionary history of small-bodied anthropoids in Asia. This discovery presumably provides only a limited perspective on the total anthropoid diversity in this region during the early Oligocene because it represents only one locus, and, furthermore, there is an apparent taphonomic bias because of size sorting regarding large-bodied mammals: only small [Bugtilemur,
100 g (25); Phileosimias,
250 g; and Bugtipithecus,
350 g] to medium-sized [Guangxilemur,
2 kg (24)] primate taxa have been unearthed thus far.
The demonstration that anthropoids persisted in southern Asia raises the critical issue of their subsequent evolution. Early Neogene anthropoid communities from South Asia consist of members of the Dionysopithecidae, a group of primates generally considered as stem pliopithecoids among catarrhine anthropoids (40), which seemingly entered Asia from Africa (19, 40) by the early Miocene (as part of the well known faunal interchanges that occurred as a result of the collision between the AfroArabian and Eurasian plates) or even earlier, during the Oligocene (41, 42). The eventual extinction of eosimiids and amphipithecids may have resulted from a phenomenon of competitive exclusion when pliopithecoids arrived in South Asia. However, the possibility of continuity and Asian ancestry for some of the Miocene Asian anthropoids from Paleogene Asian forms (43), although widely contested (17, 19, 40), cannot be totally precluded in the light of these discoveries from the Oligocene of Pakistan. In many ways, the dental morphology of the genus Bugtipithecus and, in particular, the morphology of its upper molars, is strikingly reminiscent of that of dionysopithecids, notably Dionysopithecus shuangouensis Li, 1978 (44). For instance, upper molars of both taxa exhibit a strong development of the prehypocrista linking the strong hypocone to the postprotocrista, have a strong and continuous hypoparacrista connected to the preprotocrista, which is limited lingually (lack of a labial extension, i.e., preparaconule crista), and show a labial extension of the anterocingulum (mesial fovea). These upper molar similarities between Bugtipithecus and Dionysopithecus are not observed in the Propliopithecidae (Aegyptopithecus, Propliopithecus, and Moeripithecus), the group of primates from the Oligocene of AraboAfrica customarily regarded as stem catarrhines, in which pliopithecoids are usually nested (40). Upper molars of Bugtipithecus differ, however, from those of Dionysopithecus in showing an important degree of waisting lingual to the metacone, a minute metaconule, and having a stronger parastyle. Lower molars of Bugtipithecus also differ substantially in lacking the pliopithecine triangle but also in lacking a strong hypoconulid and the distal fovea. Additional paleontological data are therefore necessary for evaluating whether these striking dental resemblances between amphipithecids and dionysopithecids are the result of functional convergences related to dietary specializations or are phylogenetically significant apomorphies.
| Acknowledgements |
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Abbreviations: DBC2, Dera Bugti locus C2; UMC, Université Montpellier II Collections.
To whom correspondence should be addressed. E-mail: marivaux{at}isem.univ-montp2.fr.
© 2005 by The National Academy of Sciences of the USA
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