Say Hello to the “Smallrus” | Natural History Museum of Los Angeles

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Say Hello to the “Smallrus”

This extinct walrus is the smallest known to science

A recreation of the “smallrus” by Eduardo J. Cruz Vega.

 

Today there is only one species of walrus — the enormous, mustachioed, tusked marine mammal. But millions of years ago there were several different species in this family.

NHMLA Assistant Curator of Marine Mammals Jorge Velez-Juarbe studies the evolution of walruses and their relatives. In a recent study, Velez-Juarbe describes a new species of dwarf walrus, nicknamed the “smallrus.”

Based on the left mandible (lower-jaw) and teeth, Jorge Velez-Juarbe has named this new species Nanodobenus arandai — "Aranda's dwarf walrus.” The name honors Francisco Aranda-Manteca, the retired curator of paleontology at the Universidad Autonoma de Baja California in Ensenada.

a photo of the walrus diorama at the museum, with four individual walruses lounging on a slab of ice
The walrus diorama in the North American Mammal Hall here at NHM shows the modern day walrus, but one extinct relative of this marine mammal was just half the size.

With a body length a little over 5 feet, it is the smallest walrus ever known. (Today’s walrus is nearly twice that length.) It swam the shorelines of Baja California between 15 and 9 million years ago alongside baleen whales, sea lions, and desmostylians — an extinct, hippo-like marine mammal.

"I was surprised when I first saw the specimen,” says Velez-Juarbe. “The teeth were like those I had seen in some fossil walruses, but a fraction of the size, and all indications pointed to it being from an adult. I immediately knew I was staring at a new species."

The presence of this previously unknown dwarf walrus shows that we are still a long ways to fully understand pinniped (the group that includes seals, sea lions, and walruses) diversity in the Eastern Pacific region.

a photo of fossil walrus jaws. the one of this new species if by far the smallest
The jaw of newly-described Nanodobenus arandai is small compared to its evolutionary relatives.

 

 

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