TEXAS RED BEDS AND THE FIRST LAND MASS EXTINCTION: EARLY PERMIAN NEAR SEYMOUR SHOWS TWO DISTINCT LARGE HERBIVORE COMMUNITIES, BOTH EXTERMINATED SIMULTANEOUSLY WHILE LARGE AQUATICS SURVIVED
Two habitats occur: The Craddock Ranch Mudstone Facies: Discovered in 1882, this unit records the famous Arroyo red beds fauna. Fine-grained sediment, mostly red, punctuated by zones of caliche nodules and thin roots, filling temporary ponds and well drained floodplains; edaphosaurids rare; diadectids common. Large amphibians are rare but smaller diplocaulids and trimerorhachids are very common. The commonest apex predators are dimetrodonts, mammal-like reptiles, contributing 93% of the carnivore shed teeth and carnivore bones. The George Ranch Mudstone Facies: Discovered in 2014, this is the first-known outcrop with abundant skeletons of the last and largest edaphosaurid, Edaphosaurus pogonias. Silty-sandy mudstone and sheet sandstones, dull greenish-brown, with many thick horizontal roots but few caliche zones, filling swampy lakes and adjacent forest floor; diadectids rare; edaphosaurids extremely common. Small amphibians are rare. Commonest apex predators are alligator-like eryopid amphibians, contributing 90% of the shed teeth and carnivore bones. In their preferred habitats, both herbivore families were common shortly before the extinction. The biggest aquatic predator, eryopids, survived, as did small aquatic amphibians, all with little morphological change. This first land extinction exhibits the same ecological selectivity of the classic Late Cretaceous and Pleistocene die-offs.