99 



independently in Martes and the pinnipeds (DELTRAN optimization), or jointly for the 

 mustelids and the pinnipeds, with Lutra reversing to the plesiomorphic condition 

 (ACCTRAN optimization). 



31) amount of bone reduction along maxillo-frontal suture in interorbital region: 0 = none 

 / irregular perforations; 1 = little - small foramen or narrow fissure; 2 = great - large 

 foramen and/or greatly widened suture (Burns & Fay 1970; pers. obs.) (state 1 - Fig.20). 

 So-called "defects" in the ossification of phocid skulls are reasonably common and have 

 repeatedly been mentioned (Mivart 1885; Howell 1928; Burns & Fay 1970; King 1972), 

 but have rarely been utilized in a systematic context. Perhaps the largest and most 

 consistently present defect occurs in the interorbital region and corresponds to a widening 

 of the maxillo-frontal suture. This defect (frequently referred to as the orbital vacuity) is 

 irregularly shaped, but roughly crescentic in shape and often confluent with the 

 sphenopalatine foramen of the palate (Burns & Fay 1970; see also character #43). The 

 size of the widened maxillo-frontal suture is quite variable in the phocids, generally large 

 in the otariids, and small or absent in the fissiped carnivores (Howell 1928; Burns & Fay 

 1970). One potential complicating factor is the report that the size of the suture apparently 

 decreases with age in the lobodontines (de Muizon & Hendey 1980)? ^ 

 A widened suture is generally absent outside of the phocids, being found only for Ursus 

 (state 1 - small foramen located at lacrimo-maxillo-palatine suture) and Zalophus (state 

 2 - large irregularly shaped foramen occupying most of anterior orbital wall together with 

 the broadly confluent sphenopalatine foramen). The two phocid subfamilies are clearly 

 differentiated by this feature, with virtually all phocines (Pagophilus being the notable 

 exception) possessing a slightly widened suture (state 1), and virtually all monachines 

 sharing a greatly expanded suture (although the lobodontines are generally polymorphic 

 between states 1 and 2). Together with Zalophus, a large amount of bone loss along the 

 maxillo-frontal suture may be a synapomorphy of the pinnipeds as a whole (ACCTRAN 

 optimization), or it may have arisen independently in the otariids and the monachines 

 (DELTRAN optimization). 



*32) morphology of bone reduction along maxillo-frontal suture in interorbital region: 0 

 = none; 1 = irregular perforations; 2 = round / ovoid; 3 = inverse teardrop-shaped; 4 = 

 roughly rectangular; 5 = crescent-shaped (Burns & Fay 1970; pers. obs.) (Fig.20). 

 Although reasonably reflective of the major shapes for the widened maxillo-frontal sutures 

 of phocids, this character is too particular and was recoded as the more general #3 1 in an 

 attempt to generate more synapomorphies. 



*33) shape of maxillary (anteroventral) edge of widened maxillo-frontal suture: 0 = 

 concave; 1 = straight; 2 = convex; 9 = n/a - maxilla and frontal in contact (pers. obs.) 

 (Fig.20). 



This character was abandoned in favour of #31 in an attempt to generate a succinct 

 summary of the widening of the maxillo-frontal suture in phocids. 

 *34) shape of frontal (posterodorsal) edge of widened maxillo-frontal suture: 0 = concave; 

 1 = straight; 2 = convex; 9 = n/a - maxilla and frontal in contact (pers. obs.) (Fig.20). 

 This character was abandoned in favour of #31 in an attempt to generate a succinct 

 summary of the widening of the maxillo-frontal suture in phocids. 



