Humeral head shape as an indicator of locomotor behavior in extant strepsirhines and Eocene adapids

Postcranial material from Notharctus, Smilodectes and Cantius is abundant and well studied, but debate continues over whether the locomotor repertoire of these animals included a substantial component of vertical leaping. Here, the shape of the humeral head of 11 genera of extant strepsirhines, Notharctus, Smilodectes and Cantius was quantified using serial mediolateral and proximodistal contours. Univariate and multivariate analyses of these data show that vertically leaping strepsirhines have a distally relatively high narrow humeral head compared to arboreal quadrupeds and it places Notharctus and Smilodectes in a group with Hapalemur griseus, while Cantius is grouped with Eulemur macaco, suggesting that a quadrupedal form preceded the appearance of vertical leaping.