104 



Fig.21: Dorsal view of a fron- 

 tally-sectioned felid (Felis 

 domestica) cranium illustra- 

 ting selected characters (indi- 

 cated by their number; see 

 Character Analysis) of this 

 region. Anterior is towards 

 the top of the page. Adapted 

 from Gilbert (1968). 



#49). This might be especially true for the monachines, as the least interorbital width in 

 this subfamily occurs in the middle or posterior portion of the interorbital region (King 

 1972; Wyss 1988a), or, in other words, around the region of the orbitosphenoid. 

 Our observations, however, do not substantiate this line of reasoning. Instead, the 

 apomorphic interorbital septum is an uncommon occurrence, being found in only 

 Zalophus, Monachus monachus, and Monachus tropicalis (the latter of which also 

 possesses an anteriorly located least interorbital width; see character #49). The presence 

 of the septum in the two monk seals might indicate a synapomorphy of the genus as a 

 whole, with a reversal in Monachus schauinslandi (ACCTRAN optimization), or simply 

 parallel evolution in each species (DELTRAN optimization). 



47) continuity of bilateral optic foramina (interorbital foramen) in interorbital region: 0 = 

 not continuous, no common passage; 1 = continuous, form passage through interorbital 

 region (Mitchell 1975) (Fig.20). 



Mitchell ( 1975) noted that a patent interorbital foramen [i.e., where the left and right optic 

 foramina are continuous medially (either in whole or in part), thereby creating a foramen 

 that pierces the interorbital region] was diagnostic of otariids and of the primitive fossil 

 pinniped Allodesmus kernensis. Although we observed that continuity of the foramina is 

 aided by their sharing of a common rostral border, this is not an absolute requirement, as 

 the distribution of this character differs slightly from that of the previous one. Again, the 

 apomorphic continuity of the foramina is uncommon, occurring as expected in Zalophus, 

 but also independently in Martes and Monachus monachus. 



48) alisphenoid canal: 0 = absent; 1 = present (Wozencraft 1989). 



The distribution of the alisphenoid canal is one of the key characters supporting the 

 diphyletic hypothesis of pinniped ancestry. Along with other evidence, the occurrence of 

 the canal in otarioids together with its lack in phocids has led some workers to ally the 



