Comparative anatomy of the major blood vessels of the sealions Neophoca and Phocarctos; with comments on the differences between the otariid and phocid vascular systems



The major blood vessels of the sealion pups Neophoca cinerea and Phocarctos hookeri are described, and the results compared with descriptions in the literature of the vascular systems of phocoid and otarioid seals. The arteries of pinnipeds, in general, follow the normal mammalian plan, but modifications have occurred in the venous system. These modifications have been well documented for many phocids, but in the eared seals and walruses limited information suggests differences from the phocid pattern. Eared seals and walruses have a venous system much more like that of a typical mammal and they do not appear to have pericardial rete, or a typical phocid renal stellate plexus, or enlarged extradural vein; while they do possess normal renal veins and venous drainage of the head by the external jugular vein.