96 



Fig.20: Dorsolateral view of the left interorbital region (see inset) of Cystophora cristata (USNM 

 188914) illustrating selected characters (indicated by their number; see Character Analysis) of this 

 region. Anterior is towards the right of the page and dorsal to the top, with the zygomatic arch framing 

 the bottom of the illustration. Abbreviations are as follows: FR = frontal; MAX = maxilla; OR = 

 orbitosphenoid; PAL = palatine; PAR = parietal; and SQ = squamosal. Scale bar equals 1 cm. Inset 

 adapted from Lawlor (1979). 



Among pinnipeds, the general distribution of this feature is for it to be present in the 

 otarioids, but only rarely so in the phocids (Mivart 1885), a difference Howell (1928) 

 attributed to details of the orbicularis oculi and possibly the frontalis muscles. Turner 

 (1848) questioned the value of this character for discriminating between the pinnipeds as 

 it was present both throughout the otariids and in representative phocids (e.g., Hydrurga). 

 A variable distribution in the pinnipeds is echoed by Hendey & Repenning (1972). Except 

 for Hydrurga and Lobodon, the preorbital process is generally small in monachines, if not 

 altogether absent, as in Leptonychotes, Monachus schauinslandi, and Monachus tropicalis 

 (Mivart 1885; Hendey & Repenning 1972; de Muizon & Hendey 1980). Among phocines, 

 Burns & Fay (1970) used the size of the preorbital process as one means of distinguishing 

 between the closely related genera Pagophilus, Pusa, Histriophoca, and Phoca (listed in 

 descending order of process size). In fissiped carnivores, the process is lacking in all but 

 Lutra and Ursus, where it is rudimentary (Mivart 1885). 



In contrast to the observations of Mivart (1885), we found a distinct preorbital process in 

 all fissiped taxa expect Procyon. The plesiomorphic condition is for a small process, with 

 an increase to medium size denoting a synapomorphy of the lutrines and the pinnipeds. 



