Current status of pinnipeds phylogeny based on molecular and morphological data

Abstract

ABSTRACT The disagreement surrounding the relationship within pinnipeds as well as their phylogenetic affinities still remains unresolved. Molecular-based studies neglect significant morphological data and ignore the entire fossil record, which demonstrates why there are such contradicting results from morphology-based studies. There still remains a difference of opinion about the origin of pinnipeds, with research supporting origination from either Ursid (bear-like) or Mustelid (weasel-like) ancestors, even extending down to familial and subfamilial levels. This study examines certain morphological characters in the three pinniped families: Otariidae (sea lions and fur seals), Odobenidae (walruses), and Phocidae (true seals), with extra emphasis on the four phocid subfamilies: Phocinae, Monachinae, Cystophorinae, and Devinophocinae. Morphological characters of the cranium (skull, dentition and mandible) and post cranium (humerus and femur) are the basis for understanding pinnipeds’ movement, body size, and sexual dimorphism, and all are ignored when only molecular analyses are used. Biomolecular based studies involve larger sample sizes and incorporate more phylogenetic characters, but ignore the significant data from the fossil record (which can only be examined through morphology). Therefore, the origin of pinnipeds cannot be resolved by depending only on molecular (genetic) or morphological approaches independently and future studies need to integrate both morphology and molecular data.