Skull development and growth in the southern fur seals Arctocephalus forsteri and A. pusillus doriferus (Carnivora : Otariidae)

Abstract

Cranial development in skulls of New Zealand and Australian fur seals (Arctocephalus forsteri and A. pusillus doriferus) was compared and found to be similar. The complete closure of cranial sutures showed little variation in sequence for either species but was generally slower in males. Based on suture closure, females matured earlier than males and showed monophasic growth. Males matured later and expressed monophasic growth for some characteristics but a secondary growth spurt for others. The former included variables that were of shared functional importance (e.g. growth of the braincase plus characteristics related to hearing, breathing and feeding). The latter occurred in features related to biting and structural support of the skull. Not all males exhibited biphasic growth in these characteristics, which may reflect the existence of multiple mating strategies or interpopulation growth differences. Variation in size was greatest in physiologically mature specimens and occurred mainly in those variables that expressed sexually dimorphic development.