88 



Fig. 18: Dorsal view of the 

 snout of Monachus tropicalis 

 (USNM 102536) illustrating 

 selected characters (indicated 

 by their number; see Charac- 

 ter Analysis) of this region. 

 Anterior is towards the top of 

 the page. Scale bar equals 

 1 cm. 



always visible , ' did not always share the same location for that portion of the process that 

 slips into the nasal aperture. As well, the all-encompassing character is inapplicable for 

 genera such as Cystophora, Mirounga, and Ommatophoca. where the nasal processes are 

 absent dorsally. Therefore, in order to minimize potential homoplasy and to maximize the 

 applicability of this character for all species, we split the nasal processes into three equal 

 portions (dorsal, middle, and ventral) and viewed each separately. 



For the ventral portion of the nasal processes, the derived condition (state 1) is limited to 

 only those monachines internal to Hydrurga. Within this clade. the polymorphic taxa 

 Monachus schauinslandi and Monachus tropicalis show partial reversals to the 

 plesiomorphic condition. This likely represents another synapomorphy of these two taxa, 

 although this is not indicated here due to the manner in which PAUP handles polymorphic 

 data (Swofford 1993: see Methods and Materials). 



6) visibility of middle portion of nasal processes of premaxilla along maxilla in lateral 

 view: 0 = always visible: 1 = not always visible: 9 = n/a - middle portion not present (de 

 Muizon 1982a: Wyss 1988a). 



For the suite of characters involving the visibility of the nasal processes of the premaxilla. 

 the middle portion is probably the most important systematically. This middle portion is 

 the one most often identified as defining the monachine condition, whereby the nasal 

 processes are not always visible (Hendey & Repenning 1972: de Muizon & Hendey 1980; 



