New primate carpal bones from Rudabánya (late Miocene, Hungary): taxonomic and functional implications

We describe a scaphoid and two capitates from the late Miocene site of Rudabánya, Hungary using qualitative and quantitative comparisons to a large sample of hominoid, cercopithecoid, and platyrrhine primates. The scaphoid (RUD 202) is not fused to the os centrale and in this way is like most primates other than African apes and humans (hominines). Qualitatively, its morphology is most similar to Pongo, and univariate analyses generally confirm an ape-like morphology with an increased range of mobility. One capitate (RUD 167) is compatible in size to the scaphoid, and its morphology suggests a combination of monkey-like generalized arboreality and ape-like enhanced mobility. RUD 203 is a smaller, fragmentary capitate, about half the size of RUD 167, and preserves only the distal portion of the body with the third metacarpal articular surface. Its morphology is virtually identical to that of RUD 167, and an exact randomization test revealed that it is statistically likely to find two carpal bones of such disparate sizes within one taxon. However, due to morphological similarities with other Miocene hominoids as well as implications for size variation within one taxon and sex, we consider the taxonomic affiliation of RUD 203 to be unresolved. We attribute the scaphoid and RUD 167 capitate to the hominine Rudapithecus hungaricus (formerly Dryopithecus brancoi; see Begun et al., 2008) based on overall morphological similarity to extant apes, particularly Pongo, and not to the pliopithecoid Anapithecus hernyaki, the only other primate known from Rudabánya. The similarities in carpal morphology to suspensory taxa are consistent with previous interpretations of Rudapithecus positional behavior. The scaphoid and the RUD 167 capitate are consistent in size with a partial skeleton including associated postcranial and craniodental specimens from the same level at the locality and may be from the same individual. These are the first carpal bones described from Rudabánya and from this taxon, and they add to our understanding of the evolution of arboreal locomotion in late Miocene apes.