162 



towards a straighter posterior flipper margin (Wyss 1988a). As the outline of the posterior 

 flipper could not be observed directly, we concentrated instead on the relative size of the 

 third metatarsal. 



Most fissipeds are characterized by the plesiomorphic state, whereby the third metatarsal 

 is the longest, although Enhydra and Ursus independently obtain state 1. A shortened third 

 metatarsal is diagnostic of the pinnipeds, with the otarioids generally obtaining state 2 

 while the phocids derive state 3 ancestrally. No separation between the two phocid 

 subfamilies was obtained here, as virtually all taxa retained a distinctly shortened third 

 metatarsal. Again, this is due, in large measure, to the historically rather arbitrary 

 distinction between the phocine and monachine morphologies ("slightly shorter" versus 

 "distinctly shorter") that was difficult to quantify here. Only Pusa caspica [as obtained 

 from Wyss (1988a)] and Histriophoca convergently reverse towards the typical fissiped 

 pattern by obtaining state 2. If this observation for Histriophoca is accurate, then a severe 

 shortening of the phalanges of the third hind digit must account for the concave posterior 

 flipper margin reported for this genus (see above). 



189) relative degree of development of hind flipper claws: 0 = not well developed or 

 absent; 1 = well developed, prominent (King 1966; Wyss 1988a). 



As with the foreflippers (see character #169), there exists a tendency towards reduction 

 of the hind flipper claws in the pinnipeds. For the phocids at least, the pattern is more 

 unmistakable. Phocines again have well developed hind flipper claws, while those of all 

 monachines are markedly reduced (King 1966, 1983; Wyss 1988a). The otariids now 

 present something of a categorical problem, as the hind flipper claws are large, but are 

 only present on the middle three digits (Howell 1928; King 1983; Wyss 1988a). Odobenus 

 presents less of a problem. Although it likewise possesses the three grooming claws, they 

 are quite small (King 1983; Wyss 1988a). Missing data were again supplemented with 

 observations from King (1966). 



The apomorphic reduction of the hind flipper claws occurs independently on three 

 occasions within the Caniformia: Enhydra, the otarioids generally (Zalophus is regarded 

 here as being polymorphic for this character), and the monachines. This may be a 

 synapomorphy of these taxa, with Lutra and the phocines re-obtaining large claws 

 ( ACCTRAN optimization), or be the result of parallel evolution (DELTRAN optimization). 



Miscellaneous (7 characters) 

 This section includes hard anatomical characters that did not fall into the other categories 

 and selected soft anatomical features. 



190) location of posterior end of cribriform plate: 0 = within interorbital region; 1 = 

 posterior portion of interorbital region; 2 = anterior end of braincase (pers. obs.) (Fig. 19). 

 Perhaps associated with the lateral compression of the interorbital region of the pinnipeds 

 (Howell 1928; King 1972, 1983; see character #49), we noted that the posterior end of 

 the cribriform plate in this group is generally shifted posteriorly. Instead of lying distinctly 

 within the (anterior end of the) interorbital region, as in most caniforms, the plate in all 

 pinnipeds is located within the posterior end of the interorbital region, or, at its most 



