114 



subfamily), but also appears in two phocines, Cystophora and Pagophilus. This comes 

 about either as a synapomorphy of the monachines alone, with convergent appearances in 

 the two phocines (DELTRAN optimization), or as a synapomorphy of the phocids as a 

 whole, with an early reversal in the phocines, followed by a re-derivation in Pagophilus 

 (ACCTRAN optimization). 



70) orientation of pterygoid hamuli: 0 = directed laterally; 1 = in midline; 2 = directed 

 medially (Mivart 1885; Allen 1887; Chapskii 1955a). 



The orientation of the pterygoid hamuli appears to be directed by one, and possibly, two 

 factors. The function of the hamuli is to suspend the soft palate over the internal nares. 

 Therefore, the width of the soft palate will directly influence the direction of the hamuli. 

 A second possible influence involves the origin of the pterygoideus externus (= medialis) 

 from the adjacent pterygoid fossa (Davis 1964). Changes in the robustness of this muscle 

 might indirectly affect the hamuli. An increase in robustness (e.g., in those taxa employing 

 a more grinding masticatory motion) may serve to direct the hamuli inwards, whereas a 

 decrease in robustness would cause the orientation to be determined more by the hamuli's 

 primary function. Descriptions of hamular orientation are rare, but laterally directed hamuli 

 have been noted in Leptonychotes (Mivart 1885), Monachus tropicalis (Allen 1887), and 

 isolated phocines (Chapskii 1955a, 1967). Chapskii (1967) hints at an apparent shift from 

 medially to laterally directed hamuli during the ontogeny of Phoca largha. Otherwise, 

 only Erignathus has been noted to possess medially directed hamuli (Chapskii 1955a). 

 All fissiped caniforms are characterized by hamuli situated in the midline, with apomorphic 

 deviations from this occurring only in the pinnipeds. Medially directed hamuli occur 

 convergently in Mirounga spp., and either in Odobenus alone (DELTRAN optimization), 

 or in the otarioids as a whole (ACCTRAN optimization). However, like all other pinnipeds, 

 none of these taxa are known to employ a grinding style of mastication. Laterally directed 

 hamuli are peculiar to the phocids, appearing independently in Halichoerus and the clade 

 of monachines internal to Hydrurga (with Monachus monachus reversing to the 

 plesiomorphic condition). A relative reduction of the pterygoideus externus has not been 

 described in phocids (see Howell 1928; Bryden 1971; Pierard 1971), and it is not known 

 if these taxa possess a proportionately wider soft palate. 



*71) relationship of ethmoid to pterygoid process of basisphenoid on ventral surface of 

 skull: 0 = does not contact pterygoid; 1 = contacts pterygoid (pers. obs.). 

 With recoding, this character was included in character #72. 



72) degree of contact between ethmoid and pterygoid process of basisphenoid: 0 = narrow; 

 1 = greater than or equal to medium breadth; 9 = none (pers. obs.). 

 Among the Caniformia, the pterygoid process of the basisphenoid extends to different 

 degrees both anteriorly and posteriorly (see character #73 for the latter). In the anterior 

 direction, we observed two major mechanisms for preventing (or minimizing) contact 

 between the ethmoid and the pterygoid process. Either the two elements did not approach 

 each other closely, or if they did, then contact was prevented by the presence of the 

 pterygoid canal (sensu Burns & Fay 1970). In some cases, the canal was too small to 

 prevent contact absolutely and merely minimized the amount of contact (e.g., changing a 

 potentially broad contact to a narrow one). 



