The Rocky Mountains' diverse cast of carnivores

March 20, 2017
Burke Museum

By Susumu Tomiya

I was hooked on the paleontology of mammals in my junior year of college when I took a seminar taught by Dr. Ken Rose at Johns Hopkins. I was mesmerized by the dark shiny teeth of mammals that he had brought back from his field sites in Wyoming, and became fascinated by the history of mammalian diversity. I then went on to pursue graduate study in biology at UC Berkeley. For my dissertation, I studied the evolution of Eocene carnivores (about 46 to 40 million years old) recovered from urban development sites in southern California. 

Susumu Tomiya holding a fossil of an extinct wolf-like carnivore, Mesonyx obtusidens

Photo by Burke Museum

I am broadly interested in the ecological processes and environmental histories that have shaped – and continue to influence – the diversity of mammals such as competition, climate change, and habitat modification by humans. A lot of my effort to date has gone into documenting the past diversity of land mammals – especially those that lived in North America from 50-37 million years ago and the last ~20,000 years – through taxonomic research, which includes describing new species and figuring out where they fit on the tree of mammals. I have also investigated patterns of extinction in the fossil record, ultimately to better understand the long-term consequences of today's biodiversity crisis.

Related to my research, I am passionate about taking care of natural history collections. When I work in museums, I often find myself making foam liners for specimens (which protect them from breakage), correcting misidentifications of animals, or obsessively restoring the proper order of specimens in drawers. Research collections are in some ways like community gardens--when everyone (including researchers) takes good care of them, there will be more knowledge to harvest for everyone.  I spent a lot of time during my week at the Burke re-identifying Eocene fossils from the Bridger and Washakie Basins of Wyoming.

A collection of mammal fossils, with both carnivourous and non-carnivourous specimens. 

Photo by Burke Museum

In addition, I spent a day or so hunched over a tray of bone fragments, extracting parts of a young individual of a new carnivore species that I am describing for publication – one of only two known specimens of this new carnivore (one at the Field Museum, the other at Burke) that will help us take another step toward resolving the origin of carnivorans (dogs, cats, and their relatives). 

A closer look at the wolf-like carnivore Mesonyx obtusidens, which is from Wyoming and roughly 50 million years old 

Photo by Burke Museum 

A scene from the Washakie Basin of southwestern Wyoming, ca. 46 million years ago.

Illustration by Adrienne Stroup of the Field Museum, used with permission

I also took hundreds of close-up photos of small teeth using the museum's high-tech digitization station, which automates much of the process of taking dozens of pictures of one object at different focus levels (e.g., 50 photos for a tooth that's ~3 mm tall) and digitally stack them to produce a single extremely sharp image. 

Tray of bone fragments including parts of a young individual of a new carnivore species that Susumu is describing for publication

Photo by Susumu Tomiya

Tooth of carnivore species that Susumu is studying

Photo by Susumu Tomiya

It was an exciting and productive visit thanks to support from the paleontology collections staff – the part of the collection I looked at has a lot of potential for future research. I really appreciate the collections study grant, especially as a postdoctoral scientist who has limited options for funding museum visits.


Susumu Tomiya is a postdoctoral researcher at Des Moines University (Des Moines, IA) and a research associate of the Field Museum (Chicago, IL) and the University of California Museum of Paleontology (Berkeley, CA).

See more fossils in the Vertebrate Paleontology collection or learn more about the Vertebrate Paleontology Collection study grant.

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