Giant Ice-Age 'Longhorn Bison' Unearthed in San Diego

Highway workers have unearthed the fossilized bones of an unusual giant bison in a suburb of San Diego, the first such discovery in Southern California.

The fossil may date back as much as 200,000 years -- not long after bison first appeared in what's now the United States.

Paleontologists at the San Diego Museum of Natural History say the newfound specimen is likely the species Bison latifrons -- the longhorn, or giant, bison -- one of the truly "mega" megafauna that grazed the American West during the last major Ice Age.

Skull and horn cores of Bison latifrons on display at American Museum of Natural History

Giant bison resembled the species you see today, with a couple of notable exceptions -- they were about 25 percent bigger overall, standing about 2.5 meters at the shoulder, and they sported horns as much as three times longer, measuring some 1.7 meters from tip to tip (5.6 feet) on average.

They also differed in their habits from modern bison, making their homes in forests and woodland clearings, rather than grasslands, and living in small groups instead of the massive, plains-blackening herds in which Bison bison roamed the West as recently as 150 years ago.

Contractors found the new fossil in April near the town of Bonsall, about 72 kilometers (45 miles) north of downtown San Diego, while excavating a highway interchange between two major interstates. The remains were identified by museum paleontologist Brad Riney, who was monitoring the project, and were moved to the San Diego Natural History Museum, where they were unveiled today and will be prepared for display.

The fossil bison skull in plaster cast (left) with photo of prepared skull to show orientation (Credit: Donna Raub)

As the first giant bison found in Southern California, the newfound bones can add significantly to our understanding of B. latifrons' range, particularly since it may date to just a few ten-thousand years after the species was first thought to have migrated from the ice-covered north.

But it's by no means the first fossil bison found in Southern California. Ancient remains of the modern bison's direct ancestor, Bison antiquus, have been found nearby at Diamond Valley Lake and, even more famously, at Los Angeles' La Brea Tar Pits, where it's the most common large herbivore represented.

Giant bison, like the one unveiled today, disappeared about 30,000 years ago, but Bison antiquus lived on, in time giving rise to the bison that now survive, if barely, on preserves and private ranches throughout the West.

You can explore the fossil as Dr. Riney walks you through the excavation in this video provided by the San Diego Natural History Museum:



Sources:

• South Dakota Tech Museum of Geology: Bison evolution
• North Dakota Department of Mineral Resources: Occurrence of the Giant Ice Age Bison, Bison latifrons, in North Dakota
• "Late Pleistocene distribution of Bison (Mammalia; Artiodactyla) in the Mojave Desert of Southern California and Nevada," Geology and Vertebrate Paleontology of Western and Southern North America (2008)