QUANTIFYING PHALANGEAL CURVATURE - AN EMPIRICAL-COMPARISON OF ALTERNATIVE METHODS

It has been generally assumed and theoretically argued that the curvat ure of finger and toe bones seen in some nonhuman primates is associat ed with cheiridial use in an arboreal setting. Assessment of such curv ature in fossil primates has been used to infer the positional behavio r of these animals. Several methods of quantifying curvature of bones have been proposed. The measure most commonly applied to phalanges is that of included angle, but this has come under some criticism. We con sider various other approaches for quantifying phalangeal curvature, d emonstrating that some are equivalent to use of included angle, but th at one-normalized curvature moment arm (NCMA)-represents a true altern ative. A comparison of NCMA to included angle, both calculated on manu al and pedal proximal phalanges of humans, apes, some monkeys, and the Hadar fossils, revealed that these two different measures of curvatur e are highly correlated and result in very similar distributional patt erns. (C) 1995 Wiley-Liss, Inc.