Anthracosaurians

Anthracosaurians are an extinct group of tetrapods that lived during the Carboniferous and Permian periods. Their fossil record suggests they were an early offshoot of the reptile lineage, often referred to as "reptiliomorphs" or "anthracosaurs." These creatures occupied a transitional position between the first amphibians and the true reptiles, exhibiting a mix of traits from both groups.

Morphologically, anthracosaurians generally possessed stout bodies, strong limbs, and long tails. Their skulls showed a pattern of bones that was more reptilian than amphibian, particularly in the structure of the temporal region. Evidence suggests some anthracosaurians may have been semi-aquatic, while others were likely terrestrial, preying on insects and smaller vertebrates.

The exact phylogenetic placement of anthracosaurians has been a subject of debate among paleontologists. However, current consensus places them as a paraphyletic group, meaning they do not form a single, distinct evolutionary lineage that includes all their descendants. They are considered significant in understanding the evolutionary transition from aquatic to terrestrial life and the early diversification of amniotes. Their extinction is thought to be linked to environmental changes at the end of the Permian period.