142 



139) tendency to lose accessory cusps in triconodont postcanines: 0 = absent; 1 = present; 

 9 = n/a - postcanines not triconodont (Chapskii 1955a). 



The other variant on the triconodont morphology is to lose some or all of the accessory 

 cusps, a tendency associated with a change in diet to softer foods (Chapskii 1955a). 

 Occasionally, this loss is so extreme that the tooth appears to be unicuspate, as in 

 Halichoerus or Leptonychotes (Mivart 1885; Chapskii 1955a; Ridgway 1972). Other taxa 

 noted for the loss of the accessory cusps include Phoca spp. (Ridgway 1972) and, to 

 varying degrees of severity, Histriophoca (Chapskii 1955a; Scheffer 1960). State 9 is 

 plesiomorphic for this character. The trend toward losing the accessory cusps is a 

 synapomorphy of the phocines (with and without Cystophora), and virtually universal, 

 missing only in Pusa sibirica (possibly as a synapomorphy with Pusa hispida; ACCTRAN 

 optimization). In those monachines where this character is applicable, the tendency appears 

 only in Monachus monachus, and is lacking in Hydrurga and Monachus schauinslandi 

 (possibly as a synapomorphy with Monachus tropicalis; ACCTRAN optimization). 



140) size of accessory cusps in triconodont or multicuspate postcanines: 0 = small, 

 continuous with major cusp; 1 = larger, distinct from major cusp; 9 = n/a - postcanines 

 not triconodont or multicuspate (de Muizon 1982a; pers. obs.). 



Triconodont postcanines may occur convergently in both the phocines and monachines 

 (see character #137). This is somewhat corroborated by the different morphologies of the 

 accessory cusps in applicable phocines (state 0), and in Hydrurga and Lobodon among 

 the monachines (state 1) (de Muizon 1982a). A Hydrurga-Lobodon pairing among 

 lobodontines has frequently been advocated on the basis of their distinctive postcanine 

 morphology (Hendey 1972; de Muizon & Hendey 1980; de Muizon 1982a; King 1983). 

 We have limited the distribution of this character to the pinnipeds (automatically rendering 

 state 9 as plesiomorphic), and to those pinnipeds with triconodont or multicuspate teeth 

 in particular. Apomorphic, small accessory cusps are universal among the phocines, with 

 and without Cystophora. Both apomorphic states are found in the monachines: state 0 for 

 Monachus spp. at least, possibly as a synapomorphy of the clade Lobodon, Monachus 

 spp., plus Ommatophoca (ACCTRAN optimization); and state 1 for Hydrurga and 

 Lobodon only. The convergent possession of state 1 in the latter two taxa speaks against 

 their previous pairing within the lobodontines. 



141) relative size of upper postcanines: 0 = all subequal; 1 = #1 (PM') noticeably smaller 

 than rest, which are subequal; 2 = #5 (M 1 ) noticeably smaller than rest, which are subequal; 

 3 = #1 and #5 noticeably smaller than rest, which are subequal; 4 = #1 and/or #5 noticeably 

 larger than rest, which are subequal; 9 = n/a - postcanine homology uncertain (Allen 1887; 

 Scheffer 1960; de Muizon & Hendey 1980). 



The relative sizes of both the upper and lower postcanines appear to contain a good deal 

 of potential systematic information. Unfortunately, any such value is tempered by the 

 problematic nature of both characters. In attempting to summarize the vast amount of 

 variation present throughout the phocids, we concentrated on the first and last postcanine, 

 which appeared to present the clearest and most consistent trends throughout the family 

 (see also Allen 1887; Scheffer 1960). In particular, McLaren (1960a) apparently holds a 

 small last molar to be diagnostic of Pusa spp.; however, this reduction of M 1 may be a 



