Where did fossil evidence show ancient walrus relatives flourishing during the Miocene?

In temperate coastal areas like Orange County, California

Paleontological discoveries, specifically those unearthed in areas such as Orange County, California, reveal that the ancestral relatives of the modern walrus occupied vastly different environments than today. During the Miocene epoch, these ecosystems were significantly warmer and more temperate, supporting at least three distinct extinct walrus species. This evidence contradicts the notion that the walrus lineage was always restricted to frigid waters. The presence of diverse, large, specialized marine mammals in this region demonstrates that the evolutionary cradle for the Odobenid family was geographically much more temperate before major global cooling necessitated a specialized adaptation to the high Arctic regions.