Announcing Mammut pacificus, the Pacific Mastodon

HEMET, CA – The Western Science Center is proud to announce Mammut pacificus, the Pacific mastodon. This is the first new mastodon species from North America named in over 50 years, and the announcement arrives almost a quarter of a century after the initial discovery of “Max” the mastodon during the Diamond Valley Lake excavation project. Western Science Center’s Executive Director Dr. Alton Dooley was lead author on the paper, now published in the open access journal PeerJ.

The Metropolitan Water District of Southern California began the Diamond Valley Lake excavation in 1995; at the time it was the largest earthworks project in North America. The project led to the discovery of over 100,000 fossils, including what is now one of the largest collection of mastodons in the country, which were considered relatively rare in California prior to this discovery.

Coauthor Kathleen Springer of the United States Geological Survey led the original DVL excavation conducted by the San Bernardino County Museum. “We always knew it would require further research to understand [these fossils’] true importance,” says Springer. “The naming of a new species of mastodon through the continued study of these fossils makes me incredibly proud.”

According to coauthor Eric Scott of Cogstone Resource Management, who was also part of the original excavation team, “… we nicknamed the site the ‘Valley of the Mastodons’ because it seemed like every day brought in more mastodon fossils – bones, teeth, even partial skeletons. It was this surprising wealth of material that made the recognition of this new species possible.”

Ice Age mastodons from California were previously assigned to Mammut americanum. The new species is defined by proportionally narrower teeth, as well as differences in the hips and hind legs. The holotype specimen of the new species is a Diamond Valley Lake mastodon known as “Max”, the largest mastodon ever found in California and currently on exhibit at Western Science Center. However, the Pacific mastodon is not unique to Diamond Valley Lake; specimens can be found at the La Brea Tar Pits and Museum, Natural History Museum of Los Angeles County, San Diego Natural History Museum, and throughout California.

The discovery of the differences between M. americanum and M. pacificus came about completely by accident. “We were trying to update some of Max’s exhibit panels,” says Dr. Dooley. “While doing research for these panels we found anomalies in his tooth measurements. From there, one thing led to another; four years later, the result is this paper!”

The authors of the paper examined over 400 mastodons from more than two dozen museums across North America to collect the necessary data. The data collection was funded by Mastodons of Unusual Size, an crowdfunding campaign supported by 29 backers.

Research like this underscores the importance of museum collections and institutions like the Western Science Center, which has housed the specimens found during the Diamond Valley Lake excavation since its opening in 2006. “More than half of all Pacific mastodon specimens known are from Diamond Valley Lake; Metropolitan Water District had the foresight to work with paleontologists during the construction of the reservoir to make sure these remains were collected and put in a museum for future study,” says Dr. Dooley.

Max and many other Diamond Valley Lake fossils are the centerpieces of the Western Science Center’s main exhibit hall and are currently on view to guests. 3D models of M. pacificus are now available for download at Sketchfab and MorphoSource, and the paper itself is open access and can now be downloaded on PeerJ’s website.

Mammut pacificus Fact Sheet


  • Alton C. Dooley, Jr., Western Science Center (lead)

  • Eric Scott, Cogstone Resource Management

  • Jeremy Green, Kent State University

  • Kathleen Springer, United States Geological Survey

  • Brett S. Dooley, Western Science Center

  • Gregory J. Smith, Vanderbilt University

History & Science

  • M. pacificus lived during the Pleistocene epoch, which spanned from approximately 2 million years – 10,000 years ago.

  • M. pacificus specimens have so far been identified throughout California and from southern Idaho.

  • In comparison to M. americanum, M. pacificus is defined by the following features: narrower teeth, a proportionally thicker femur, six sacral vertebra, and an absence of mandibular tusks in all growth stages.

  • M. pacificus teeth were found in California as early as the 1860s during gold mining in the Sierra Nevada foothills and were originally assigned to M. americanum.

  • Mastodons are members of the mammalian order Proboscidea, which includes living elephants; however, mastodons are only distantly related to elephants and mammoths.


  • In addition to the Western Science Center, some other museums that have displays of M. pacificus specimens are on display at the La Brea Tar Pits and Museum, Natural History Museum of Los Angeles County, San Diego Natural History Museum, Santa Barbara Museum of Natural History, and San Bernardino County Museum.

Education & Outreach

  • In 2017 the Western Science Center hosted the Valley of the Mastodons conference and exhibit, which brought mastodon experts from across North America. All of the paper’s authors attended, and many of the discussions at that conference contributed to this research.