VEGGIE-SAUR DEBUT?:EARLIEST COPROLITE FROM HI-FIBER LARGE TETRAPOD, EARLY PERMIAN, SEYMOUR, TX

Today, large tetrapod herbivores (100 kg plus) disturb floral architecture by toppling woody plants, excavating roots, and selective browsing. When did large land hi-fiber herbivores first evolve? The earliest widespread forests, Late Devonian, about 380 million years b.p., probably produced enough vegetable matter to feed a large hi-fiber herbivore. Arthropods and some small tetrapods may have eaten plants beginning in Late Devonian/Early Carboniferous. However, large tetrapods apparently were slow to enter this feeding guild. Vertebrates digesting hi-fiber vegetable organs require multiple shearing tooth crests and/or gizzard stones, plus enlarged gut compartments for microbes that contribute enzymes to break down tough cell walls. The earliest known large tetrapods so equipped seem to be edaphosaurids and diadectids, “reptile-grade” amniotes appearing in very late Carboniferous. Both families increased body size so by mid Early Permian they exceeded 100 kg.

Can we be certain that these families were, indeed, hi-fiber herbivores? It has been suggested that edaphosaurids crushed mollusks; diadectid teeth might have been used for a mix of soil animals and roots. Coprolites can test hypotheses, though herbivore feces, low in phosphate and carbonate, often are rare. In the Lower Clear Fork, mid Early Permian, at Seymour, Texas, coprolites are exceptionally varied and well preserved. Most enclose fish scales, and/or tetrapod fragments. An important site is SSQTCH, a silty limestone within a floodplain sequence yielding abundant diadectid bones. Here occur very large diadectid tracks, distinguished by wide, five-digit feet and blunt, broad claws. Five m from the tracks was a large coprolite, irregular ropes of calcareous material piled on top of each other. Skeletal fragments are absent; internal texture is like that of root casts. The coils differ from “faux feces” produced by inorganic processes in being lumpier and lacking long striae. The geometry fits “vegan snakes”, feces from human vegetarians and herbivorus geese. The Seymour specimen seems to be the earliest fecal fossil from a large, hi-fiber tetrapod herbivore, confirming that this key guild debuted with the diadectids and was absent before the Late Carboniferous.