127 



basisphenoid to extend ventrally along the medial edge of the bulla, forcing the opening 

 of the carotid canal posteriorly. In the phocines, this tendency is apparently absent and 

 the carotid canal faces more medially (King 1972). If the lack of this tendency of the 

 basioccipital and basisphenoid bones in the phocines is due to their uniquely expanded 

 petrobasilar fissure (see character #95), then one might predict that the remaining 

 caniforms will approximate the monachine condition. 



Among the arctoid carnivores, the primitive condition is for a posteriorly facing carotid 

 canal (the monachine condition) as postulated above. An apomorphic medial shift of the 

 opening of the carotid canal is found universally in the phocines [although it may not 

 characterize them ancestrally (DELTRAN optimization)], and convergently in Martes 

 (state 0) and Lobodon (state 1). Most phocines (including Erignathus, which lacks an 

 expanded petrobasilar fissure) display a medially directed canal. An intermediate shift 

 (state 1) is only found convergently in Cystophora and the clade of Histriophoca plus 

 Pagophilus. 



*100) direction of posterior opening of carotid canal, II: 0 = roughly 90° (i.e., medially); 

 1 = distinctly greater than 45° medially but distinctly less than 90°; 2 = roughly 45° 

 medially; 3 = distinctly less than 45° medially but distinctly greater than 0°; 4 = roughly 

 0° (i.e., posteriorly); 9 = carotid canal absent (pers. obs.) (Fig. 22). 

 This character represents an inferior coding (with respect to character #99) of the direction 

 of the posterior opening of the carotid canal, as it is too particular and thus limits the 

 number of potential synapomorphies. Therefore, it was abandoned in favour of the 

 previous character. 



101) posteromedial bony shelf of auditory bulla extending from aperture of carotid canal 

 to posterior lacerate foramen: 0 = absent; 1 = rudimentary or present; 9 = carotid canal 

 absent (Wyss 1988a) (Fig.22). 



As with character #97, Wyss (1988a) described the absence of the bony shelf in phocines, 

 exclusive of Erignathus [a distribution echoed by Burns & Fay (1970)], as being an 

 apomorphic trait attributable to the inflated auditory bulla of this group. However, if this 

 is the case, the similar possession of an inflated bulla in most other arctoid carnivores 

 should cause the shelf to be absent in these forms as well, rendering this feature a 

 symplesiomorphy of the group. Our analysis indicates this to be the case, with the apo- 

 morphic possession of the shelf being limited to Erignathus and the clade of the lobodon- 

 tines plus Monachus spp. Of this latter group, Monachus monachus re-obtains the primitive 

 morphology. The shelf may be developing in the polymorphic Enhydra. 



102) dorsal wall of carotid canal: 0 = open; 1 = closed; 9 = carotid canal absent (pers. 

 obs.) (Fig.22). 



Our observations of the basicranial region of the otarioids revealed a peculiar morphology 

 involving the carotid canal and the posterior lacerate foramen. In all the phocids and most 

 other arctoids we examined, the carotid canal is completely encircled by the caudal 

 entotympanic of the auditory bulla, so that its opening is separate from the posterior 

 lacerate foramen. However, in the otarioids, the dorsal wall (which is rotated more 

 medially in Odobenus and the phocids Mirounga spp. and Ommatophoca) of the carotid 

 canal is incomplete, and its foramen is confluent posterodorsally (or posteromedially for 



