Mesopithecus

Abstract: The endocast of Aegyptopithecus, a 27 million year old ape, reveals that its brain was advanced over that of prosimians and comparable to that of modern anthropoids in relative size and in having expanded visual cortex, reduced olfactory bulbs, and a central sulcus separating primary somatic sensory and motor cortex. The early appearance of those features suggests that they may have been among the adaptations responsible for the evolution of anthropoids from prosimian ancestors. The frontal lobe was relatively smaller in Aegyptopithecus than in modern anthropoids. An endocast of Dolichocebus, one of the oldest known New World monkeys (25–30 million years old), reveals visual cortex expanded as in modern anthropoids. The 19 million year old Napak frontal bone displays a hominoid rather than cercopithecoid sulcal pattern. An 18 million year old endocast of the ape Dryopithecus (Proconsul) was neither monkey-like nor primitive, as originally described, but rather apelike and essentially modern in all observable features. The oldest undoubted Old World monkey endocast, from nine million year old Mesopithecus, reveals that the brain was modern in sulcal pattern and proportions. The sulcal pattern was like that of modern colobines, but that appears to be the more primitive condition, from which features characteristic of modern cercopithecine brains have evolved. The brain of six million year old Libypithecus was similar to that of Mesopithecus. A two million year old endocast of “Dolichopithecus” arvernensis displays a modern cercopithecine sulcal pattern.

Abstract: Introduction The question of whether the earliest cercopithecoids were adapted for folivory or frugivory has implications for understanding the divergence of Old World monkeys and apes. Because the molars of all modern cercopithecoid monkeys are bilophodont, and most mammals with lophodont dentition eat leaves, the origin of Old World monkeys is commonly associated with a trend toward the inclusion of more leaves in their annual diets than in those of primitive apes and basal catarrhines (Jolly, 1970; Napier, 1970; Simons, 1970; Delson, 1975a,b, 1979; Andrews, 1981; Temerin and Cant, 1983; Andrews and Aiello, 1984). The first suggestion that the earliest monkeys may not have been folivorous, but instead were highly frugivorous, came from an analysis of shear crest lengths (predominantly the lengths of cusp margins) on the lower second molars of the middle Miocene Victoriapithecus (Kay 1975, 1977a). Kay (1975, 1978, 1984) and Maier (1977a,b) proposed that cercopithecoid bilophodonty evolved as a consequence of selection for an efficient grinding mechanism: lophs act as guides for interlocking cusps and basins during occlusion; the size of the entoconid grinding facet is expanded; and the functional life of the crown is lengthened by increasing crown height. Some proponents of the analogy-based scenario argued that two species existed within the Victoriapithecus sample, one interpreted to be a frugivorous cercopithecine, and the other a more folivorous colobine based on its supposedly longer shear crests (Delson, 1975a,b, 1979; Simons and Delson, 1978; Szalay and Delson, 1979). The more frugivorous species was depicted as eating leaves facultatively.

Abstract: Th e presence of the cercopithecids in the Neogene of Greece is known since the beginning of the 19th century. Th e excavations of the last 20 years increase their number in Greece. Th e main taxon of the cercopithecids is Mesopithecus Wagner, 1839 found originally in the middle Turolian (MN 12) locality of Pikermi, near Athens. Th e Pikermi Mesopithecus sample is rich and belongs to a medium-sized form, M. pentelicus Wagner, 1839. Besides the well-known M. pentelicus, two other species were recognized. Th e new species M. delsoni Bonis, Bouvrain, Geraads & Koufos, 1990, a large-sized form found in the early Turolian (MN 11) locality Ravin des Zouaves-5 of Axios Valley (Macedonia, Greece) has several diff erences from the type species. In the middle Turolian (MN 12) localities of Vathylakkos (Axios Valley) and Perivolaki (Th essaly) a large to medium-sized Mesopithecus form with “delsoni” and “pentelicus” characters was found and is referred to as M. delsoni/pentelicus. A small-sized form named M. cf. monspessulanus was recognized by a mandibular fragment in the late Turolian (MN 13) locality Dytiko-2 of Axios Valley and indicates the early appearance of the taxon at the end of Miocene. Th e rest of the material found in the late Turolian localities of Dytiko has some diff erences from the typical M. pentelicus. Moreover, Mesopithecus was traced in several late Miocene localities, indicating its wide distribution in Greece. Two other cercopithecids were also found in the Pliocene of Greece. Dolichopithecus ruscinensis Deperet, 1889 was recognized in the locality of Megalon Emvolon and in Ptolemais Basin (Macedonia, Greece); both are dated to late Ruscinian (MN 15). Th e second Pliocene cercopithecid is Paradolichopithecus arvernensis (Deperet, 1929), found in the locality of Vatera (Lesvos Island) and dated to late Pliocene. Th e stratigraphic distribution and the palaeoenvironment of these cercopithecids are also discussed.