1878 - Edaphosaurus - Pelycosaur

From Wikipedia:
Edaphosaurus is a genus of prehistoric reptile which lived around 303 to 299 million years ago, during the late Carboniferous to early Permian periods. The name Edaphosaurus means "ground lizard" and is derived from the Greek edaphos ("ground, land") and sauros ("lizard").

This genus was first known from remains discovered in North America, in the late 19th century, and described by American paleontologist Edward Drinker Cope. More recently other fossils attributed to Edaphosaurus have been found in the Czech Republic and Slovakia.

The most characteristic feature of Edaphosaurus is a sail on its back similar to that of other reptiles of the same time, such as the large apex predator Dimetrodon. However, the sail on Edaphosaurus is different in shape and morphology. Along with the reptile-like family Diadectidae, Edaphosaurus is one of the earliest known large plant-eating tetrapods (land-living vertebrates). Early descriptions, referring to its sharp teeth, suggest that the reptile may have fed on small invertebrates, such as mollusks, although paleontologists now point out that Edaphosaurus also shows herbivore characteristics.