Ice Age bison remains found in Fallbrook

History has knocked on Fallbrook’s door, and paleontology specialists are working diligently to interpret the message.

Caltrans and the San Diego Natural History Museum (SDNHM) announced May 10 that fossilized remains of an Ice Age bison were found April 10 during grading work conducted as part of the construction of the new Interstate 15/ State Route 76 interchange in Fallbrook.

The museum’s curator of paleontology, Tom Demere, PhD, compared the paleontological site to a CSI crime scene, “The spine bones were found in one spot and the skull in another.” He surmised that “the bison was scavenged after death. The bones not found (those from the rump, fore limbs and lower jaw) were the fleshy or meatiest areas of the body. Although the complete skull was not found, the find is exciting in that it is the most complete set of bones of a bison found in this region.”

Paleontologist Brad Riney noticed the fossilized bones in the area being cleared for the new northbound onramp to Interstate 15 at State Route 76. The fossils consist of a series of upper back, lower back, and sacral vertebrae articulated with the pelvic bones. The skull of the bison was discovered buried about eight feet away. Two days after the find and having been encased with their immediate surrounding sediment in plaster jackets, the fossils were transported to the museum where they are currently being cleaned and readied for study and display.

According to Demere, “The area where the bison was found is part of the ancestral San Luis Rey River Valley, which was heavily forested at that time.”

The bison would have measured “about 15 feet from snout to rump besides being about 8 feet tall at the shoulders. It was most likely a female due to its size. Bison were sexually dimorphic: the males were larger than the females.”

Demere also said the bison lived about the same time as the saber tooth cats, dire wolf, sloth, etc., during the Pleistocene Epoch approximately 200,000 years ago and went extinct about 20,000 years ago. A sample of the fossil will be sent to the United States Geological Survey (USGS) in Denver for radiocarbon dating to pinpoint its precise age.

The details for displaying the bison fossils are still being worked out, experts said. They may be placed in the lobby temporarily but most likely will be available for viewing in the family demo lab, third floor of the museum in approximately a month and a half.

Demere said, “From the find we can learn about the past. It gives a direct window into evolution to help us understand diversity in ecosystems. Organisms reflect the environment in which they live.”

Experts at the museum said, “These are the most complete bison fossils ever recovered from San Diego County and represent a new record for the region. The discovery serves to expand our knowledge of the overall distribution of these animals in western North America and provides insight into the ancient ecosystems that characterized our area during the Ice Ages.”

Cal Trans District 11 Director Laurie Berman spoke about Cal Trans’ partnership with the SDNHM and said “over 1,000 important fossils” have been found during roadwork in the county.

When asked if the discovery delayed work on the highway, Berman said the two days (of recovering the fossils) was not a long interruption and the new interchange is on schedule to open in late summer.

Suzanne Moramarco, collections technician at the San Diego Archaeological Center, contributed to this article.