CLAW RETRACTION AND PROTRACTION IN THE CARNIVORA - SKELETAL MICROVARIATION IN THE PHALANGES OF THE FELIDAE

All carnivorans retract and protract their claws, In felids and some v iverrids the claws of digits II through V of both the manus and pes ha ve a larger are of rotation than those of other carnivorans; the claws retract to the lateral side of the middle phalanx rather than onto it s dorsal surface as in most other carnivorans. This condition should b e termed hyper-retraction. Morphological features of the middle and di stal (ungual) phalanges that have been purported to be necessary for h yper-retraction in felids vary considerably among digits within the ma nus and pes, These features include the lateral projection of the dist al head and the asymmetry of the shaft of the middle phalanx, and the oblique orientation of the articular surface on the distal phalanx. No ne of these features is necessary in every instance for hyper-retracti on, and some of the variation in these features is associated instead with protraction. Differences among digits in the orientation of the a rticular surface on the distal phalanx are associated with differences in the degree to which the claws must move laterally to rotate from t he protracted to the retracted position. Differences in the orientatio n of the distal head on the middle phalanx are associated with the spr eading of the claws during protraction. The manual claws are hook-shap ed, whereas the pedal claws are more blade-like; this morphological di fference is associated with differences in function between the manus and pes. In the manus the medial claws have a larger radius of curvatu re and a smaller angle of are as compared to the more lateral claws; i n the pes, the claws on digits III and TV have larger radii of curvatu re and smaller angles of are. Digit I of the manus lacks the hyper-ret raction mechanism; nonetheless, this digit shares many of the attribut es that are associated with this mechanism. (C) 1996 Wiley-Liss, Inc.