8 



The taxonomic status of the genera within the Phocini 



The tribe Phocini is comprised of the genera Halichoerus, Histriophoca, Pagophilus, 

 Phoca, and Pusa. Together, they are apparently clearly distinguished from the remaining 

 phocids by the presence of a white natal coat (lanugo) (McLaren 1960a, 1966, 1975), a 

 reduced karyotype of 2N = 32 (Arnason 1974, 1977), and numerous morphological 

 characters (King 1966; Burns & Fay 1970). Of the five constituent genera, the distinctive 

 nature of Halichoerus has long been recognized, it being the first seal to be separated 

 from the original, all-encompassing seal genus Phoca (see Chapskii 1955a; Scheffer 1958). 

 Halichoerus is the largest of the phocines, and is typified by a long, high, and wide snout 

 which gives it a "Roman nose" in profile (King 1972, 1983; Bonner 1981). Modifications 

 of the nasal region parallel those in Cystophora and Mirounga, and to such a degree that 

 it is often considered that Halichoerus should also possess some form of nasal appendage 

 (King 1972). 



Differences between the remaining members of the Phocini are slight. Despite being 

 individually recognizable, the features of the skulls of each genus overlap to such a degree 

 that Burns & Fay (1970) subsumed the four taxa as subgenera within a newly defined 

 Phoca (also Doutt 1942). Halichoerus, although closely related to the remaining Phocini, 

 was not included in the newly defined Phoca due to an insufficient sample size to allow 

 proper re-designation, coupled with sufficient cranial differentiation to allow it to be 

 clearly set apart (Burns & Fay 1970). 



However, this exclusion of Halichoerus does not appear to be justified. Arnason et al. 

 (1995) note that the cranial characters used to distinguish Halichoerus would not merit 

 generic distinction within the terrestrial carnivores, a point conceded by Burns & Fay 

 (1970). In addition, most biomolecular studies indicate either no or equal difference 

 between all the constituent genera of the Phocini (e.g., McDermid & Bonner 1975; Baram 

 et al. 1991; Arnason et al. 1993; Arnason et al. 1995). Perhaps of more importance is the 

 contention that Halichoerus is more closely related to the clade of Phoca (sensu stricto) 

 and Pusa than either genus is to Histriophoca and Pagophilus (Chapskii 1955a; McLaren 

 1975; de Muizon 1982a; Mouchaty et al. 1995; Perry et al. 1995), thus rendering Phoca 

 (sensu Burns & Fay) paraphyletic. A similar arrangement, with similar consequences for 

 Phoca (sensu Burns & Fay), has been suggested infrequently between Cystophora and the 

 clade of Histriophoca plus Pagophilus (de Muizon 1982a; Perry et al. 1995). [In any case, 

 the close morphological similarity of Histriophoca and Pagophilus has been noted on 

 many occasions (Chapskii 1955a; Davies 1958b; McLaren 1975), but may be based on 

 symplesiomorphies (de Muizon 1982a).] As well, there are reports of interbreeding 

 between Halichoerus and either Pusa hispida or Phoca vitulina in captivity (Chapskii 

 1955a; Scheffer 1958). In view of recent statements that the generic distinction afforded 

 Halichoerus is inappropriate unless it is also applied to the subgenera of Phoca (sensu 

 Burns & Fay) (Arnason et al. 1993, 1995), we will use Phoca in the strict sense and 

 continue to recognize Histriophoca, Pagophilus, and Pusa as distinct genera. 

 In any case, phylogenetic resolution among the Phocini is generally poor. Most authors 

 advocate two roughly equally derived main clades falling along Halichoerus-Phoca-Pusa 

 and Histriophoca-Pagophilus lines (Chapskii 1955a; de Muizon 1982a; Arnason et al. 



