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

Cuvieran mass extinctions on land strike large herbivore families most severely; large and small fresh water aquatics survive almost untouched. The event penetrates most habitats, from swampy forests to treeless plains, and most victims are common up to the final event. Examples: the Late Pleistocene event and the end of the Cretaceous. The earliest Cuvieran event is in the mid Early Permian, when both families of mega-herbivores (body 100kg and greater), the diadectids and edaphosaurids, disappear. Did extinction penetrate all habitats simultaneously? Were the mega-herbivores common right before the event? And did aquatics persist? We investigated the lower Clear Fork Group, north of Seymour, Texas, where are found large samples of tetrapods that lived shortly before the herbivore extinction.

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.