They are also highly vascularized and covered in unusually large mental foramina, indicating that Pelagiarctos may have had somewhat fleshy lips.

The remains of Pelagiarctos have so far only been discovered in the Sharktooth Hill Bonebed, located in Kern County, California.

[1] The bonebed is approximately 15.97 - 13.65 million years old, and is interpreted to have been laid down in a coastal environment off the shore of the Miocene North Pacific.

The sediments that have yielded Pelagiarctos have also yielded numerous other species of ocean-going vertebrates, including sharks (Isurus, Sphyrna, Carcharocles), turtles (Psephophorus), seabirds (Osteodontornis, Diomedea, Puffinus), Cetaceans (Prosqualodon, Aulophyseter, Parietobalaena) and other pinnipeds (Allodesmus, Neotherium).

If so, it would make Pelagiarctos unique among pinnipeds, as most other species are adapted to much smaller prey such as fish or squid.