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Fig. 19: Lateral view of the right side of a phocid skull (Phoca sp.) illustrating selected characters 

 (indicated by their number, with specific states presented in parentheses; see Character Analysis). 

 Anterior is towards the left of the page. Adapted from Lawlor (1979). 



of the fossa in Hydrurga), the caninus fossa is indicated here to be a synapomorphy of 

 the whole of the phocids, with a single loss occurring in the ancestor of those monachines 

 internal to Hydrurga. 



20) depth of unnamed fossa on ventrolateral side of premaxilla: 0 = shallow; 1 = medium; 

 2 = deep; 9 = absent (pers. obs.) (Fig. 19). 



Our observations of the snout region revealed a distinct depression located between the 

 last upper incisor and the upper canine in many specimens. This apparently unnamed fossa 

 of the premaxilla provides room for the lower canine when the mouth is closed, and thus 

 essentially relates to the size of the lower canine to some degree. 



The general evolutionary trend for this character is for it to decrease in size from its 

 primitive medium depth, often to the point of being entirely absent, in moving towards 

 the pinnipeds. A shallow fossa is a synapomorphy retained from Procyon into each phocid 

 subfamily. From there, several independent losses of the fossa occur, most notably in the 

 clade of Erignathus, Histriophoca, and Pagophilus, and in those monachines internal to 

 Hydrurga, with Monachus spp. showing a tendency to re-develop a shallow fossa. 

 Mirounga spp. uniquely derives a deep fossa. Overall, this distribution likely reflects the 

 trend towards homodonty in the pinnipeds, with large canines being secondarily reacquired 

 in the sexually dimorphic Mirounga spp. (see also King 1983). 



21) anterior opening of infraorbital canal relative to nasolacrimal foramen: 0 = anterior; 

 1 = ventral (or posterior) (Wozencraft 1989). 



Although we are using the character as suggested by Wozencraft (1989), he goes on to 

 suggest that this character may be more accurately recoded as referring to the relative 

 length of the rostrum, noting that those taxa with long rostra also possess an anterior 

 placement of the anterior canal opening. Several phocids are noted for their long rostra 

 [e.g., Cystophora, Hydrurga, Lobodon, and Mirounga; King (1972)], but this may only be 



