The Paleontology Collection at the Mayborn Museum Complex contains over 13,500 fossil specimens. Over 70% of these are fossils that were collected in Texas. The majority are marine invertebrates, such as the oyster Exogyra ponderosa and the sea urchin Heteraster texanus.
In the 1940s, Mrs. George D. Harris donated over 1888 fossil specimens to the museum. Collected between 1932 and 1935 by her husband, all of these fossils are from central Texas.
The collection also includes a 75-million-year-old giant sea turtle, Protostega gigas. Discovered in 1971, it took almost two years to be excavated and is currently on exhibit at the Mayborn Museum Complex. Also on exhibit are the fossilized remains of a Ceraunosuarus brownorum, a marine reptile that swam in the shallow sea that covered central Texas during the Cretaceous Period.