Colosteidae

Colosteidae is a family of stegocephalians (stem-group tetrapods) that lived in the Carboniferous period. They possessed a variety of characteristics from different tetrapod or stem-tetrapod groups, which made them historically difficult to classify. They are now considered to be part of a lineage intermediate between the earliest Devonian terrestrial vertebrates (such as Ichthyostega), and the different groups ancestral to all modern tetrapods, such as temnospondyls (probably ancestral to modern amphibians) and reptiliomorphs (ancestral to amniotes such as mammals, reptiles, and birds).

Greererpeton burkemorani ("crawler from Greer, West Virginia") is an extinct genus of colosteid stem-tetrapods from the Early Carboniferous period (late Viséan) of North America. Greererpeton was first described by famed vertebrate paleontologist Alfred S. Romer in 1969, based on a skull and partial skeleton from the Bluefield Formation. The skull was redescribed by Timothy R. Smithson in 1982, while postcranial remains were redescribed by Stephen J. Godfrey in 1989. thumb|left|Life restoration by Dmitry Bogdanov Greererpeton were probably aquatic, with an elongated body adapted for swimming.

Colosteus is an extinct genus of colosteid tetrapod from the Late Carboniferous (late Westphalian stage) of Ohio. Its remains have been found at the Linton site in Saline Township, Ohio, where it is one of the most common tetrapods, and at the Five Points site in Mahoning County, Ohio. It was an elongate, aquatic form with a flattened and pointed head, greatly reduced limbs, two premaxillary tusks, and heavy scalation. It would have reached about 1 m (3.2 ft) in length.

Pholidogaster ('scaly stomach') is an extinct genus of stem-tetrapod that lived during the Middle Carboniferous period (late Viséan to early Serpukhovian). Pholidogaster is known from only two specimens found in Gilmerton, Scotland. Historically it was one of the first to show science the evolutionary link between fish and amphibians.