128 



Odobenus) with the posterior lacerate foramen. As this condition also occurs in some basal 

 arctoids (Mart es and Ursus), the primitive state for the arctoids becomes equivocal. 

 However, all reconstructions favour independent origins of this trait between the otarioids 

 (where it is synapomorphic), Meines, and Ursus. 



103) unidentified bone encircling posterior opening of carotid canal: 0 = absent; 1 = 

 present; 9 = carotid canal absent (pers. obs.) (Fig.22). 



This character describes a feature peculiar to, and apparently universal among, Monachus 

 schauinslandi. In this species, the posterior opening is at least partially encircled (but 

 usually completely so) by a bone distinct from the remainder of the auditory bulla. The 

 identity of this bone is uncertain. It may represent a second caudal entotympanic element, 

 as found in, or postulated for, most of the close phocid relatives advocated here: ursids, 

 otarioids, lutrines, and mephitine mustelids (see Hunt 1974). It has been suggested that a 

 second element may arise during the ontogeny of the Type B bulla possessed by phocids 

 (Wincza 1896; as cited in Hunt 1974). Or, it may merely represent an unfused portion of 

 the single caudal entotympanic. To our knowledge, despite being apparent in some 

 photographs of the basicranial region of M. schauinslandi (e.g., King and Kenyon 1961), 

 this feature has never been described before. 



104) opening of carotid canal in auditory bulla: 0 = anterior or anteroventral to posterior 

 lacerate foramen; 1 = adjacent to posterior lacerate foramen; 9 = carotid canal absent 

 (Wozencraft 1989). 



An anterior opening of the carotid canal relative to the posterior lacerate foramen diagnoses 

 all arctoids except ursids, which uniquely possess an adjacent placement within this group 

 (Wozencraft 1989). This distribution was observed here; however, the basal location of 

 Ursus (which possesses state 1 as an autapomorphy) within the arctoids renders the 

 plesiomorphic state of this character equivocal for this group. As well, Mirounga leonina 

 and Ommatophoca were polymorphic for this character. 



* 105) median lacerate foramen in auditory bulla: 0 = absent; 1 = present (pers. obs.). 

 With recoding, this character was included in character #106. 



106) size of median lacerate foramen: 0 = small; 1 = medium; 2 = large; 9 = absent (pers. 

 obs.). 



The median lacerate foramen (= anterior lacerate foramen, external carotid foramen) 

 appears to be present in most caniforms except Ailuropoda, which is polymorphic for this 

 feature (Segall 1943; Story 1951; Davis 1964). Our observations indicate that its 

 apomorphic loss (or perhaps just its lack of distinctiveness from the musculotubular canal 

 lying immediately lateral to it) occurs in Mirounga spp. (see character #105). In the 

 remaining caniforms, the foramen is of a variable size. The plesiomorphic condition is for 

 an intermediate size (state 1), as found in Canis and Ursus, but a small foramen is quickly 

 derived after this. DELTRAN optimization holds that this latter condition is largely 

 retained, with independent derivations of a medium-sized (Monachus schauinslandi) or 

 large foramen (otarioids, Cystophora, and Ommatophoca), and of its outright loss 

 (Mirounga spp.). In contrast, ACCTRAN optimization indicates that a large foramen is 

 synapomorphic for the pinnipeds and retained ancestrally for each phocid subfamily. 



