An odd melange of marine creatures occupied the North Pacific back before the last ice age, a New Zealand researcher has found.

They include a newly discovered species that is a close relative of minke, fin and blue whales, reports Robert Boessenecker, a doctoral student in geology at the University of Otago.

That species, Balaenoptera bertae, likely plied the Pacific between 1 million and 5 million years ago, Boessenecker says. The whale would have been 15 feet to 20 feet long, slightly smaller than modern minke whales, he says in the current edition of the international journal Geodiversitas.

Studying hundreds of fossil bones and teeth he excavated off Northern California, Boessenecker assembled a record of 21 marine mammal species, including dwarf baleen whales, odd double-tusked walruses, porpoises with severe underbites and a dolphin closely related to the now-extinct Chinese river dolphin. The work took him eight years.

"The mix of marine mammals I ended up uncovering was almost completely different to that found in the North Pacific today, and to anywhere else at that time," he said in a statement Tuesday.

Primitive porpoises and baleen whales lived alongside comparatively modern marine mammals such as the northern fur seal and right whales, Boessenecker says in the journal. There were also belugalike whales and tusked walruses, which today live in the Arctic.

"At the same time as this eclectic mix of ancient and modern-type marine mammals was living together, the marine mammal fauna in the North Atlantic and Southern Ocean were already in the forms we find today."

The fossils took shape 2.5 million to 5 million years ago, before the formation of Maui and Hawaii island. The creatures probably went extinct 1 million or 2 million years ago, Boessenecker says.