SIGNIFICANCE OF PRIMATE PETROSAL FROM MIDDLE EOCENE FISSURE-FILLINGS AT SHANGHUANG, JIANGSU PROVINCE, PEOPLES-REPUBLIC-OF-CHINA

An isolated petrosal bone belonging to a diminutive primate is reporte d from Middle Eocene fissure-fills near Shanghuang (southern Jiangsu P rovince, People's Republic of China), the type locality of several new ly described primates (Eosimias sinensis, a basal anthropoid; Adapoids troglodytes, a basal adapinan; Tarsius eocaenus, a congener of extant tarsiers; and Macrotarsius macrorhysis, the first Asian representativ e of an other exclusively North American genus). Because of its fragme ntary condition and unique combination of characters, the Shaughuang p etrosal cannot be assigned unambiguously to any of the Shanghuang prim ate taxa known from dental remains. However, the possibility that the petrosal represents either an adapid or a tarsiid can be dismissed bec ause it lacks defining basicranial apomorphies of these groups. By con trast the element does present arterial features consistent with its b eing haplorhine. Deciding between the likeliest candidates for its all ocation-Omomyidae and Eosimiidea-is difficult, in part because it is n ot known what (or even whether) basicranial characters can be used to distinguish these clades. If Shanghuang petrosal is that of an eosimii d, as both direct and indirect evidence appears to indicate, the follo wing implications emerge: (1) as long suspected on other grounds, anth ropoids share a closer evolutionary history with Omomyidae (and Tarsii formes) than they do with Adapidae (and Strepsirhini); (2) the special ised basicranial anatomy of extant anthropoids and their immediate cla distic relatives is derived from a primitive precursor whose otic morp holgy was like that of omomyids in moss known respects; (3) the evolut ion of the defining dental and basicranial apomorphies of extant Anthr opoidea has been distinctly mosaic in pattern. (C) 1995 Academic Press Limited.