Comparative morphology of the pollical distal phalanx
Article first published online: 21 FEB 2003
Copyright © 2003 Wiley-Liss, Inc.
American Journal of Physical Anthropology
Volume 121, Issue 1, pages 30–47, April 2003
How to Cite
Shrewsbury, M.M., Marzke, M.W., Linscheid, R.L. and Reece, S.P. (2003), Comparative morphology of the pollical distal phalanx. Am. J. Phys. Anthropol., 121: 30–47. doi: 10.1002/ajpa.10192
- Issue published online: 2 APR 2003
- Article first published online: 21 FEB 2003
- Manuscript Accepted: 16 AUG 2002
- Manuscript Received: 19 SEP 2001
- Division of Research Resources, National Institutes of Health. Grant Number: U42 RR15090-01
- flexor pollicis longus;
- distal phalangeal tuberosity;
- ungual pulp;
Functional analysis of human pollical distal phalangeal (PDP) morphology is undertaken to establish a basis for the assessment of fossil hominid PDP morphology. Features that contribute to the effectiveness of grips involving the distal thumb and finger pulp areas include: 1) distal thumb interphalangeal joint morphology, facilitating PDP conjunct pronation with flexion; 2) differentiation of a proximal, mobile pulp region from a distal, stable pulp region, providing for firm precision pinch grips and precision handling of objects; and 3) asymmetric attachment of the flexor pollicis longus (FPL) tendon fibers, favoring PDP conjunct pronation. A proportionately larger size of the ulnar vs. radial ungual spine suggests differential loading intensity of the ulnar side of the proximal ungual pulp and supporting nail bed. Stresses at the distal interphalangeal joint are indicated by the presence of a sesamoid bone within the volar (palmar) plate, which also increases the length of the flexor pollicis longus tendon moment arm. Dissections of specimens from six nonhuman primate genera indicate that these human features are shared variably with individuals in other species, although the full pattern of features appears to be distinctively human. Humans share variably with these other species all metric relationships examined here. The new data identify a need to systematically review long-standing assumptions regarding the range of precision and power manipulative capabilities that might reasonably be inferred from morphology of the distal phalangeal tuberosity and from the FPL tendon insertion site on the PDP. Am J Phys Anthropol 121:000–000, 2003. © 2003 Wiley-Liss, Inc.