138 



condition in Luira (ACCTRAN optimization), or as a synapomorphy of the pinnipeds, 

 with a parallel appearance in Enhydra (DELTRAN optimization). Two lower incisors are 

 largely retained throughout the pinnipeds, with further reductions occurring only in 

 Cystophora, Mirounga spp., and possibly Leptonychotes (all convergent origins of state 

 1), and Odobenus (state 0). 



*129) morphology of incisors: 0 = peg-like; 1 = unicuspate; 2 = caniform; 3 = complex 

 (pers. obs.). 



This character was abandoned after numerous unsuccessful attempts to accurately 

 summarize incisor shape in phocids. Any differences between the given states are highly 

 subjective and, as implied by characters #131 and 132, overall incisor morphology is not 

 constant within the series of a given species, causing additional coding difficulties. 



130) shape of upper incisors in cross-section: 0 = round; 1 = intermediate; 2 = (strongly) 

 laterally compressed (Wyss 1988a). 



Among phocids, the phocines (excluding Erignathus) are distinguished by the lateral 

 compression of their upper incisors (Burns & Fay 1970; Wyss 1988a). However, with the 

 additional observations of rounded incisors in the monachines and strongly compressed 

 incisors in the non-phocid carnivores, Wyss (1988a) interpreted the rounded condition as 

 a synapomoiphy of the phocids, with the phocines, exclusive of Erignathus, reversing to 

 the primitive compressed morphology. Histriophoca may be polymorphic for this character 

 (Burns & Fay 1970; but see Scheffer 1960). 



Although the above distribution is largely supported for the pinnipeds, only Martes and 

 Enhydra were observed to possess strongly compressed incisors among the fissipeds. In 

 contrast to Wyss (1988a), this renders rounded incisors as plesiomorphic for the caniforms, 

 and also makes the ancestral state for the phocids equivocal. Under DELTRAN 

 optimization, the primitive rounded incisors are retained through to the phocids, with the 

 laterally compressed incisors typical of the phocines becoming a synapomorphy of most 

 of this group. Meanwhile, ACCTRAN optimization holds for sequential reversals between 

 states 0 and 2, so that laterally compressed incisors become ancestral for the phocids, and 

 the trend to rounded incisors describes a synapomorphy of most of the monachines. Other 

 than Erignathus, only Cystophora (states 0, 1, and 2) and Phoca vitulina (state 1) depart 

 from the typical phocine pattern. Among the monachines, truly rounded incisors are only 

 typical of Lobodon, Mirounga spp. and Monachus spp. The remaining taxa possess either 

 state 1 (Leptonychotes and Ommatophoca) or state 2 (Hydrurga). 



131) relative size of upper incisors: 0 = outermost incisor about equal in size to remaining 

 incisor(s); 1 = outermost incisor of much greater size than remaining incisor(s); 9 = n/a 

 - only one upper incisor present per quadrant (de Muizon & Hendey 1980). 



In the phocids, the outermost upper incisor is typically larger than the remaining one (King 

 1983). This is especially true of the lobodontines, where this enlarged tooth, together with 

 the upper canine, aids in opening breathing holes in the sea ice (de Muizon & Hendey 

 1980). The lack of an enlarged outermost upper incisor in the fossil lobodontine 

 Homiphoca led de Muizon & Hendey (1980) to postulate this condition as primitive for 

 the monachines. However, our observations indicate that this morphology (i.e., state 0) is 



