117 



*77) postglenoid (= glenoid) foramen in squamosal: 0 = absent; 1 = present (Wozencraft 

 1989). 



With recoding, this character was included in character #78. 



78) size of postglenoid (= glenoid) foramen in squamosal: 0 = small; 1 = medium; 2 = 

 large; 9 = absent (Wozencraft 1989). 



The pinnipeds are supposedly unique among the Caniformia in their lack of a postglenoid 

 foramen (Wozencraft 1989), a structure that is present and generally quite conspicuous in 

 all other members of this group (Flower 1869). However, Mivart (1885) has noted the 

 presence of a small postglenoid foramen throughout the pinnipeds, while Berta (1991) 

 considers it to be either vestigial or absent within this group. The form of the foramen 

 appears to be quite variable in Histriophoca, from not being universally present to 

 occasionally being shifted laterally so as to be just anterior to the external auditory meatus 

 (Burns & Fay 1970). Our observations corroborate these last two findings, revealing that 

 the postglenoid foramen is not universally absent in pinnipeds, but instead very much 

 reduced and slightly displaced in position. In the phocids, the inflation of the auditory 

 bulla (see characters #80-82), often in combination with an enlargement of the mandibular 

 fossa, virtually eliminates the area between these structures and, as such, the foramen is 

 generally shifted onto the posterior lip of the fossa. Occasionally, we also observed a 

 lateral displacement of the postglenoid foramen equivalent to that noted by Burns & Fay 

 (1970). 



Although the postglenoid foramen is common throughout the caniforms (including the 

 pinnipeds), the high degree of polymorphism displayed by this character makes for an 

 uncertain evolutionary pathway, primarily among the outgroup taxa. The plesiomorphic 

 condition is of a large foramen, a state which may persist through to the hypothetical 

 ancestral monachine (DELTRAN optimization). Another scenario holds for a small 

 foramen being a synapomorphy linking Procyon through to the phocids (ACCTRAN 

 optimization). Beyond this disparity, there are features in common to the two evolutionary 

 scenarios. A medium-sized foramen is synapomorphic for the phocines (with an 

 independent appearance in Procyon), with Histriophoca and Pagophilus reverting to the 

 plesiomorphic condition. The monachines generally possess a small foramen, as does Pusa 

 caspica. Although a number of species were polymorphic for lacking the foramen, only 

 two were consistent for this trait: Martes and Hydrurga. 



79) shape of anterior edge of auditory bulla: 0 = concave; 1 = flat; 2 = convex (Ridgway 

 1972). 



This was another character employed by Ridgway (1972) to distinguish between the genera 

 Cystophora (state 1 to 2) and Mirounga (state 0). The plesiomorphic state is uncertain due 

 to the autapomorphic appearance of the convex morphology in Canis; however, a flat 

 morphology is both primitive and ubiquitous for the arctoids. This state is retained 

 ancestrally in the phocids, with Lutra, Halichoerus, and the monachines convergently 

 deriving a concave anterior edge. In the monachines, this morphology is often associated 

 with an unusually robust mandibular symphysis which encroaches upon the auditory bulla. 

 Lobodon plus Monachus spp. revert to the primitive arctoid state. 



