140 



feeding, as neither taxon is known to actively maintain breathing holes (Bertram 1940). 



135) number of upper postcanines: 0 = three; 1 = four; 2 = five; 3 = six (pers. obs.). 

 The trend to homodonty in the cheek teeth (with the concomitant loss of the carnassial 

 set) of the pinnipeds makes distinguishing within and between the premolars and molars 

 difficult, if not functionally unnecessary. Thus, the cheek teeth are usually collectively 

 referred to as the postcanines. However, differentiating between the postcanines is possible, 

 as four premolars and one molar per quadrant (for a total of five postcanines) have been 

 noted for most phocines, as well as for the monachines Homiphoca, Leptonychotes, and 

 Mirounga leonina (Chapskii 1955a; de Muizon & Hendey 1980; Burns 1981; Ling & 

 Bryden 1981; Stewart & Stewart 1987). This condition is likely constant (and ancestral) 

 throughout the phocids at least, although Bertram (1940) indicates that the pattern in 

 Leptonychotes and Lobodon may be one of three premolars and two molars per quadrant. 

 Despite the ease of differentiating between the cheek teeth in fissiped caniforms, we 

 likewise refer to them collectively as postcanines in an effort to identify synapomorphies 

 with the pinnipeds. 



The most common condition in the caniforms is for five upper postcanines. Canis and 

 Procyon obtain state 3, which may be symplesiomorphic (DELTRAN optimization), or 

 independently obtained from an equivocal root for the caniforms (ACCTRAN 

 optimization). Odobenus and Enhydra are autapomorphic for states 0 and 1 respectively. 

 As noted by King (1983), Zalophus is polymorphic between states 2 and 3, a condition 

 which is reflective of the otariids when viewed at the family level (King 1983). A sixth 

 upper postcanine (which was interpreted as M 2 ) occurs frequently in Halichoerus (Burns & 

 Fay 1970), but this was not supported here. 



136) number of lower postcanines: 0 = three; 1 = four; 2 = five; 3 = six; 4 = seven (pers. 

 obs.). 



As with the upper postcanines, the assessment of the plesiomorphic condition is again 

 equivocal, being either six (Martes, Procyon, and possibly Ursus) or seven {Canis only) 

 postcanines. However, the lutrines plus the pinnipeds are united by a synapomorphic 

 reduction to five postcanines, with Odobenus uniquely reducing this further to three 

 postcanines. Four postcanines were never consistently obtained at the species level. 



137) morphology of postcanines: 0 = peg-like / unicuspate; 1 = triconodont; 2 = 

 multicuspate (de Muizon & Hendey 1980). 



The wide variety of postcanine morphologies occurring within the phocids ranges from 

 the heavy, robust postcanines of Monachus spp. to the weak, often loosely rooted, ones 

 of Erignathus and Ommatophoca (King 1983). Lobodon is frequently noted for its 

 intricate, sieve-like multicuspate postcanines which are used to strain euphausiid shrimp 

 (Bertram 1940; Kooyman 1981a). Yet, despite this range, the postcanines of most phocids 

 can be traced to one form, that of the triconodont morphology, which is typified by a 

 major middle cusp with smaller to subequal cusps flanking it anteriorly and posteriorly. 

 This form is typical of the phocines (Ridgway 1972) and is postulated to be primitive for 

 the phocids, being found in such putative ancestors as Paragale and Potamotherium 

 (Hendey & Repenning 1972; de Muizon & Hendey 1980). The extant phocids are 

 characterized by the modification of this basic triconodont form, either through the loss 



