157 



175) relative length of post-acetabular region of the pelvis: 0 = shortened (and rounded); 

 1 = elongated (and narrow) (King 1966; Hendey & Repenning 1972). 



Compared with most other carnivores, the post-acetabular region of the pinniped pelvis is 

 characteristically elongated (Howell 1928; de Muizon 1982a; King 1983). The extreme 

 this condition reaches in the phocids (Howell 1928; de Muizon 1982a) is likely related to 

 the lateral eversion of the phocid ilium (see character #170). Yet, even within the phocids, 

 two different pelvis types can be differentiated. Phocines possess a relatively long and 

 narrow post-acetabular region of the pelvis, as opposed to the relatively shorter and 

 rounder form of the monachines (King 1966; Hendey & Repenning 1972). A relatively 

 elongated pelvis is synapomorphic for the mustelids (including the lutrines) plus the 

 pinnipeds. The two phocid subfamilies are clearly divided by this feature. The phocines 

 universally possess an elongated pelvis, while the monachines reverse ancestrally towards 

 a plesiomorphic short pelvis. 



176) general curvature of pelvis around long axis: 0 = relatively straight; 1 = distinctly 

 twisted (pers. obs.). 



During our observations, we noted a peculiar morphology of the phocine pelvis. In all 

 other caniforms, the pelvis is twisted around its long axis so that when the cranial portion 

 is viewed directly dorsally (i.e., so that the acetabulum points laterally), the medial surfaces 

 of the ischium and pubis are visible. In contrast, the phocine pelvis is reasonably straight, 

 so that the ischium does not deflect appreciably from the long axis of the pelvis. King 

 (1966) does note a lateral bowing of the pubis in female phocids, but this does not refer 

 to the same feature. King's (1966) bowing is more obvious in phocines and involves a 

 medial curvature of the pubis posteriorly so that the innominates are virtually in contact 

 at their posterior ends. As well, we observed the twisting under discussion here in phocines 

 of both sexes. This twisting of the pelvis is a synapomorphy of the phocines, with a parallel 

 appearance in Lobodon. 



177) relative location of ischiatic spine (= tuber ischiad): 0 = roughly midway along the 

 post-acetabular region; 1 = located in posterior post-acetabular region (pers. obs.) (Fig. 24). 

 In the caniforms, the relative location of the ischiatic spine appears to be associated with 

 the relative length of the pelvis (see character #175). In taxa with relatively short pelves, 

 the ischiatic spine tends to be located close to the posterior end of the pelvis. The apparent 

 anterior shift of the ischiatic spine in taxa with long pelves possibly indicates a posterior 

 elongation of the pelvis in these forms. However (compare with the distribution of 

 character #175), an anterior shift of the ischiatic spine is indicated to be a synapomorphy 

 of the pinnipeds, with a reversal in Odobenus (ACCTRAN optimization), or of the phocids 

 only with a parallel appearance in Zalophus (DELTRAN optimization). This latter scenario 

 accords well with observations of an elongated post-acetabular region in phocids (Howell 

 1928; de Muizon 1982a). Among phocids, only Hydrurga and Lobodon revert to the 

 plesiomorphic state (state 1). 



There is a possibility that the two states we identified for this character might be an artifact 

 of the sexual dimorphism present in pinniped pelves. King (1983) states that the posterior 

 outline of the pelvis in male pinnipeds is much more rectangular than the more rounded 

 female morphology [see Fig. 36 in King (1969)]. This would result in an apparent posterior 



