10 



fossil phocids (Ray 1976a; de Muizon 1982a). The possible paraphyly of the monachines 

 has not been adequately tested since Wyss's (1988a) analysis - studies conducted since 

 have only examined a subset of all monachines, and the only study which corroborates 

 paraphyly for the subfamily (Arnason et al. 1995) does so very weakly - and requires 

 further confirmation. 



Phocid phylogeny at the species level 



The previous three points are specific, and somewhat contentious, instances of a much 

 more pervasive problem. Overall, the species level relationships for all phocids remain to 

 be fully and adequately elucidated. Much of this can be traced to the paucity of studies 

 performed below the tribal level in phocids, where, of those studies that do, most 

 concentrate on the Phocini at the expense of the monachine tribes. Another hindrance 

 revolves around a similar lack of studies employing a rigorous methodology, and hence 

 some form of testability. Such studies are limited to the morphometric analysis of Burns & 

 Fay (1970); the cladistic studies of King (1966), de Muizon (1982), Wyss (1988a), and 

 Berta & Wyss (1994); and the molecular studies of Arnason et al. (1995), Mouchaty et 

 al. (1995) and Perry et al. (1995). However, these studies all possess one of the two 

 shortcomings mentioned above. Burns & Fay (1970), Mouchaty et al. (1995) and Perry 

 et al. (1995) only examined the phocines or a subset thereof in detail, Arnason et al. (1995) 

 included only half of all monachines, while the resolution is limited in the four cladistic 

 studies as each was essentially performed at the subfamily, generic, generic to tribal, and 

 tribal levels respectively. 



Beyond a possible lack of resolution, there is a real danger in performing cladistic analyses 

 above the species level. Such studies tacitly assume the monophyly of the higher level 

 taxa [with monophyly defined here sensu Hennig (1966): all and only the descendants of 

 a common ancestor], something that with the lack of low level systematic studies has not 

 been adequately demonstrated for most phocid taxa. Thus, we may be forcing a less than 

 optimal phylogeny of the phocids as the potential for some taxa to be paraphyletic has 

 not been allowed historically. This is classically demonstrated in the study of Berta & 

 Wyss (1994). Despite their agreement with the earlier findings of Wyss (1988a), they 

 reluctantly took Monachus to be monophyletic, causing them to question the validity of 

 their indicated phylogeny for the whole of the monachines (Berta & Wyss 1994: 43). As 

 well, studies assuming the monophyly of higher level taxa tend to make sweeping 

 generalizations concerning character states, often obscuring important, and potentially 

 informative variation within that taxon. 



Although cladistic analysis is increasingly the method of choice in phylogenetic analysis 

 (and will be used here), a cladistic solution for a species level phylogeny of the phocids 

 may prove difficult. There is some suggestion that cladistic methodology has a functional 

 lower limit around the species level, based on philosophical considerations of the species 

 and of evolution in general [de Queiroz & Donoghue (1990); Wheeler & Nixon (1990); 

 but see Vrana & Wheeler (1992) for a contrasting viewpoint]. More importantly, however, 

 there may be more immediate methodological problems threatening to impede any 

 potential cladistic solution (Arnold 1981). In any cladistic study, the exclusion of any taxa 

 (whether by choice or through circumstance) may drastically alter the resultant phylogeny. 



