It's the moment you've all been waiting for... stem-pinnipeds at Tet Zoo. Or, probable stem-pinnipeds anyway. This minimum-effort post is brought to you on the back of work showing that pinnipeds (seals, sea lions and walruses) are monophyletic, not diphyletic, and that the taxa shown here - Potamotherium, Puijila and so on - really are early members of the pinniped lineage, not convergently pinniped-like carnivorans of some sort. If there are any questions or areas of debate -- hey, that's what the comment section is for. Without further ado...

The illustrations of Semantor are from Orlov (1933). The images of Puijila, and the cladogram shown at the bottom, are from Rybczynski et al. (2009) (the cladogram is arguably odd in showing the name Pinnipedia as being attached to the entire clade rather than just to the crown-group... which isn't shown on the tree). The skeletal reconstruction of Potamotherium is from Savage & Long (1986) and the life restoration of it is by Graham Allen. For previous Tet Zoo articles on pinniped-branch carnivorans, see...

Refs - -

Orlov, Y. A. 1933. Semantor macrurus (ordo Pinnipedia, Fam. Semantoridae Fam. nova) aus den Neogen-Ablagerungen Westsibiriens. Trudy Paleontologicheskii Institut Akademiia Nauk SSSR 2, 249-253.

Rybczynski, N., Dawson, M. R., & Tedford, R. H. 2009. A semi-aquatic Arctic mammalian carnivore from the Miocene epoch and origin of Pinnipedia. Nature 458, 1021–1024.

Savage, R. J. G. & Long, M. R. 1986. Mammal Evolution: An Illustrated Guide. Facts on File Publications, New York & Oxford.