FIGURE 10.

Wing elements of a, Mancalla sp. (Alcidae, Lucas Auk; composite LACM 154560; modified from Smith (2011b, fig. 16); not to scale; oblique dorsal view) and b, Cinclus mexicanus (Cinclidae, American Dipper; rendered from CT scan of FMNH 288367; oblique ventral view). Note that in Mancalla, the ulna is shorter than both the humerus and the carpometacarpus, a condition otherwise known only in hummingbirds among all extant Aves (Smith, ^2011b). In contrast, the ulnae of dippers are longer than both the humerus and carpometacarpus but are also relatively shorter than the ulnae of thrushes. Scale bar = 3.5 mm