Patterns of evolutionary transformation in the humerus of moles (Talpidae, Mammalia): a character analysis

Abstract

Twenty-eight humeral characters were coded based on examination of osteological specimens representing 11 extant talpid genera (13 spp.) as well as two shrews and a hedgehog as outgroups. The characters were mapped onto four alternative talpid phylogenies, resulting in tree lengths ranging from 66 to 74 steps. The humerus provides a complex of characteristics that in many cases are congruent with characters from other data sets. Seven character transformations characterize the base of the talpid tree, resulting in the humerus showing the following conditions in that node: lateral edge to center of head is positioned in line with lateral edge of shaft, long axis of head at oblique angle to long axis of shaft, floor of bicipital groove is displaced medially by pectoral crest near proximal end of humerus, teres tubercle is separate from medial epicondyle, lesser tuberosity is in line with proximal edge of head or superior to head, pectoral crest forms single curved process and entepicondylar foramen is absent. When the monophyly of Neurotrichus with Urotrichus is assumed, the following derived conditions support that clade: lateral end of the lateral epicondyle has a proximally directed hook and there is a deep groove between head of humerus and greater tuberosity. A high scalopine ridge supports a clade of Scalopus and Scapanus. Several other transformations support clades that had been proposed based by previous morphological and/or molecular studies.