139 



actually apomorphic, and is found in only Procyon and Pagophilus among extant 

 caniforms. With its single upper incisor, Odobenus uniquely obtained state 9. 



132) relative size of lower 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 

 - one or fewer lower incisors present per quadrant (Scheffer 1960). 



In contrast to the previous character, the condition whereby the lower incisors are all of 

 about equal size possesses a much wider distribution and is, in fact, plesiomorphic for the 

 caniforms. State 9 tends to be indicated as a synapomorphy of the pinnipeds due to its 

 presence in Odobenus, Cystophora, and Mirounga spp. However, this is likely due to 

 convergent evolution between the three taxa, as was indicated for the lower incisor formula 

 (see character #128) upon which this character is indirectly based. Instead, in noting that 

 most phocids obtain a larger outermost incisor [as noted in Histriophoca by Scheffer 

 (1960) and Homiphoca by de Muizon & Hendey (1980)], we propose this state as a 

 synapomorphy of the pinnipeds, with Zalophus reversing to the primitive caniform 

 condition. Among phocids, only Lobodon and Pusa sibirica (possibly as a synapomorphy 

 with Pusa hispida; ACCTRAN optimization) likewise reverse to state 0. 



133) displacement of incisors (upper or lower): 0 = absent - all in line with one another; 

 1 = present - incisor series slanted; 9 = n/a - incisors absent or singular (Allen 1887; 

 Hendey & Repenning 1972). 



Typically, the incisors are positioned in line with the remaining teeth along the curvilinear 

 tooth row. Presumably, this configuration aids in the efficient dissipation of biting forces. 

 However, a slight posterior displacement of the lower medial incisor relative to the incisor 

 row has been noted in most phocids, including the fossil lobodontine Homiphoca (Allen 

 1887; Hendey & Repenning 1972). Often, this displacement only applies to the roots, with 

 the medial incisors tending to be oriented more horizontally so that their crowns line up 

 with those of the other incisors (Allen 1887). We additionally noted that the equivalent 

 condition can occur in the upper incisors as well, albeit extremely rarely. Although this 

 apomorphic displacement of the incisors is present in individual specimens of most phocid 

 species, it only manifests itself at the species level for a non-phocid, Lutra. However, 

 together with Enhydra, both Monachus monachus and Monachus schauinslandi are 

 polymorphic for this trait. This character was inapplicable for Odobenus only. 



134) procumbency of incisors (upper or lower): 0 = absent; 1 = present; 9 = n/a - upper 

 or lower incisors absent (de Muizon & Hendey 1980). 



Several phocid taxa possess the morphology whereby the upper (and less frequently the 

 lower) incisors are angled anteriorly (i.e., are procumbent). This feature is apomorphic 

 and is associated with three of the four lobodontines - Leptonychotes, Lobodon, and 

 Ommatophoca (de Muizon & Hendey 1980) - a distribution supported here. This 

 represents a synapomorphy of these taxa together with Monachus spp., which reverts to 

 the primitive condition. 



In Leptonychotes, this feature together with the large caniform morphology of the incisors 

 (see character #131) and canines function as an ice ream to keep breathing holes open in 

 the winter (Bertram 1940; King 1972; de Muizon & Hendey 1980; Kooyman 1981c). The 

 procumbent incisors of Lobodon and Ommatophoca are more likely associated with 



