ADULT ERYOPS, LARGEST SEMI-AQUATIC APEX PREDATORS OF THE TEXAS RED BEDS, LOWER CLEAR FORK, PREFERRED FAST FLOWING STREAMS, PREYING UPON EDAPHOSAURS, DIMETRODONTS AND OTHER ERYOPS

Eryops, the most massive amphibian of freshwater habitats in the Texas Red Beds, shows marked morphological conservatism throughout its exceptionally long occupancy in the semi-aquatic apex predator guild, Late Pennsylvanian to latest Early Permian. Strict habitat preference by Eryops in the rich Lower Clear Fork near Seymour, Texas, is seen in bed-by-bed sampling by the Whiteside Museum and the Houston Museum of Natural Science. Large adults preferred the George Ranch Facies, where flowing water excluded gill-breathing, bottom-clinging (GBBC) amphibians. The GBBC amphibians dominate numerically in cut-off meander lakes and floodplain ponds where adult Eryops is rare. Shed teeth and tooth marks on prey bones identify adult Edaphosaurus, a large herbivore, as Eryops prey; Dimetrodon, the top predator in floodplains, ponds and lakes, is very rare in Eryops-dominated sites; it was preyed upon by Eryops. Eryops adults fought each other and ate each other, as shown by tooth-marked snouts.

Small juvenile Eryops are rare everywhere; the single complete specimen was curled up in a mud filled burrow along the periphery of a cut-off meander lake; here bottom-clinging Diplocaulus amphibians are very common in burrows. We infer that small Eryops juveniles were sequestered in cryptic habitats. Tight suturing of palate to braincase and skull roof probably explains why Eryops is the only large Clear Fork Red Beds tetrapod usually preserved as complete skulls. The longevity of Eryops is not explained by wide habitat choice; instead this predator was specialized to exploit narrow zones not frequented by the more terrestrial dimetrodonts. The genus Alligator has a similar history in Cenozoic Americas.