Pacific Mastodon: New Species of Ancient Elephant Relative Identified

Tuesday, April 2, 2019

The Pacific mastodon (Mammut pacificus), holotype skull and tusks; a skull in: (A) dorsal, (B) ventral, (C) left lateral, (D) right lateral, (E) posterior, (F) distal end of left tusk (I1), lateral, and (G) right tusk (I1), lateral view; (A-E) images of a resin cast of the holotype skull on exhibit at the Western Science Center. Scale bar – 10 cm. Image credit: A.C. Dooley Jr et al, doi: 10.7717/peerj.6614.

A new species of mastodon that lived during the Pleistocene Epoch has been identified from fossil found in California and Idaho.

Mastodons are any species of extinct proboscideans in the genus Mammut. Often confused with mammoths, they are another, more distant, relative of living elephants.

These animals were widespread across North America and Central America during the Pliocene Epoch up to their extinction at the end of the Pleistocene Epoch around 11,000 years ago.

Over five species are currently recognized, including the well-known American mastodon (Mammut americanum) that had a widespread distribution across nearly every U.S. state, Canada, and Mexico.

The newly-identified species, named the Pacific mastodon (Mammut pacificus), was widespread in California west of the Sierra Nevada, and was present as far northeast as southern Idaho.

“For decades, the consensus on Pleistocene mastodons (which I shared) was that in North America there was only a single, widespread species, the American mastodon,” said Dr. Alton Dooley, executive director of the Western Science Center.

“Four years ago, I stumbled across the fact that California mastodons have different tooth proportions than other mastodons. A group of us started exploring that issue, trying to determine what was going on.”

Reconstruction of the American mastodon (Mammut americanum). Image credit: Sergio De la Rosa Martinez / CC BY-SA 3.0.

According to the team, the Pacific mastodon had a thicker femur and narrower teeth than the American mastodon. It had six sacral vertebrae, while the American mastodon usually had five, and had no mandibular tusks, while they still occurred in about 25% of American mastodon population.

“All known Pleistocene mastodon remains from California are consistent with our diagnosis of the Pacific mastodon, which indicates that the American mastodon was not present in California,” Dr. Dooley and colleagues said.

“Pacific mastodons were apparently absent from the Sonoran and Mojave Deserts, including from heavily sampled localities such as Tule Springs in Nevada,” the added.

“These deserts, along with the high, steep, and at times glaciated Sierra Nevada and the possible patchiness of appropriate habitats in the Basin and Range and Rocky Mountains, may have served as effective geographic barriers to mastodon dispersal.”

detailed description of the Pacific mastodon appears in the journal PeerJ.


A.C. Dooley Jr et al. 2019. Mammut pacificus sp. nov., a newly recognized species of mastodon from the Pleistocene of western North America. PeerJ 7: e6614; doi: 10.7717/peerj.6614