Abstract
A newly discovered non-mammalian vertebrate fossil assemblage belonging to the Casa Blanca Local Fauna comes from the middle Eocene Laredo Formation, Claiborne Group, of Webb County, Texas. The Casa Blanca Local Fauna includes eight chondrichthyan, six osteichthyan, one amphibian, 10 reptilian, and one avian species and is the southernmost and westernmost Paleogene vertebrate assemblage from the Gulf Coastal Plain. Four non-mammalian vertebrate taxa previously known from the Eocene of the Old World are reported from Eocene deposits of North America for the first time. The Casa Bianca Local Fauna indicates that a Tethyan marine community existed at least as far west as the Rio Grande Embayment during the middle Eocene. A new species of the osteichthyan Diaphyodus is described.