Ill 



tropicalis, our observations revealed that the anterior edge of the palatines displays other 

 distinct morphologies. This plesiomorphic condition entails the maxillo-palatine suture 

 having a rounded or triangular appearance. The flattening of this suture (manifested as a 

 straight or square anterior edge to the palatines), as in M. tropicalis, is a synapomorphy 

 of Lutra and the whole of the pinnipeds. Only Mirounga leonina and Pusa sibirica reverse 

 to re-obtain the primitive condition, although a few other species are polymorphic between 

 the two states. 



64) outline of palatine bones in ventral view: 0 = square; 1 = "butterfly-shaped" (Ridgway 

 1972). 



In essence, this character examines the entire ventral outline of the palatines and thus 

 partially overlaps both the preceding and following characters. In contrast to the previous 

 character, however, the different shapes here are determined more by the posterior half of 

 the palatines, rather than the anterior edge. As well, all three characters appear to diagnose 

 synapomorphies at different taxonomic levels. This character is apparently fairly specific, 

 as Ridgway (1972) has used it to distinguish between the genera Cystophora (state 0) and 

 Mirounga (state 1). 



An apomorphic, butterfly-shaped outline to the palatine bones is a purely phocid condition, 

 arising independently within this family on several occasions, and with numerous other 

 species being polymorphic for the trait. It tends to characterize the phocines, existing as 

 a synapomorphy of all members save Cystophora (ACCTRAN optimization), or merely 

 for the clade internal to Phoca largha, with Pagophilus and Phoca vitulina independently 

 reversing back to a square outline (DELTRAN optimization). Among monachines, 

 butterfly-shaped palatine bones only exist unequivocally for Lobodon, Mirounga 

 angustirostris, and Monachus tropicalis. The states observed here for Cystophora and 

 Mirounga generally match those described by Ridgway (1972), except that Mirounga 

 leonina obtains the plesiomorphic condition. 



65) shape of posterior edge of palatine: 0 = (roughly) triangular; 1 = arched; 2 = straight 

 (de Muizon 1982a). 



The final character involving the ventral outline of the palatines deals exclusively with 

 their posterior edge. King (1956) lists Monachus monachus as possessing a rounded 

 posterior edge, while Monachus tropicalis possesses a pointed morphology (also Allen 

 1887). Monachus schauinslandi may be polymorphic for these two states [Kenyon & Rice 

 1959; also compare King (1956) and King & Harrison (1961)]. De Muizon (1982a) has 

 pointed to a straight posterior border of the palatines as being a synapomorphy of his 

 Cystophorini (Cystophora, Histriophoca, and Pagophilus), but it may also occur 

 independently in Erignathus (Chapskii 1955a). Ridgway (1972) confirms a straight 

 posterior border for Histriophoca. However, these observations are partially contradicted 

 by Doutt (1942), who described a rounded "Roman arch" (state 1) in Histriophoca and 

 Pagophilus. This contradiction for Histriophoca may be due to it being polymorphic for 

 this trait (between states 1 and 2), as hinted at by Burns & Fay (1970). Along with 

 Monachus schauinslandi (see above), this may also be true for most species in general 

 (Chapskii 1955a). Another complicating factor is our observation that states 1 and 2 lie 

 along a continuum. A straight posterior edge may merely represent a very shallow double 



