FIRST OCCURRENCE OF HOMOTHERIUM SERUM IN THE IRVINGTONIAN SAN TIMOTEO FORMATION, SAN BERNARDINO COUNTY, CALIFORNIA

First occurrence of Homotherium serum in the Irvingtonian San Timoteo Formation, San Bernardino County, California.

Homotherium serum was a saber-toothed cat whose fossilized remains are found in small numbers over a large geographic area in North America. Biogeographic, morphological, and genetic data all indicate that Homotherium was an open habitat endurance hunter; however taphonomic and isotopic data, as well as faunal associations at Friesenhahn Cave, TX, indicate that at least one population of Homotherium serum was regularly preying on juvenile proboscideans. This led some to speculation that Homotherium may have been a proboscidean specialist.

A Homotherium serum specimen was collected in 2012 from the El Casco Substation in the Irvingtonian San Timoteo Formation by LSA Associates in southern California. It is now housed in the Western Science Center (WSC) collections, and may be one of the most complete Homotherium specimens discovered in the statetate. It is known from a dentary and a single canine, 3 cervical, 6 thoracic, and 7 lumbar vertebrae, a distal femur, and other post-cranial remains,

No proboscidean remains were recovered from the El Casco Substation and in fact, the San Timoteo Formation is notable for the near-complete absence of proboscideans in the entire unit. The presence of Homotherium at this site suggests there may well have been regional variations inof dietary preference.