apterygids

Apterygids are a group of extinct tetrapods that lived during the late Carboniferous and early Permian periods, approximately 315 to 270 million years ago. They are notable for their unique body structure and the absence of wings or forelimbs, which is why they are named "apterygids" (from the Greek "apterygos," meaning "wingless"). Apterygids are believed to have been terrestrial and semi-aquatic, with some species exhibiting adaptations for both environments.

The most well-known apterygids are the seymouriamorphs, which include the genus Seymouria, known for its distinctive body shape and the presence of a large, flat tail fin. Seymouria is often referred to as the "fish with legs" due to its combination of aquatic and terrestrial features. Other notable apterygids include the genus Eryops, which had a more terrestrial lifestyle and is considered one of the earliest known amniotes, or egg-laying vertebrates.

Apterygids are significant in the study of tetrapod evolution because they represent a transitional stage between early amphibians and the more advanced amniotes. Their diverse body forms and adaptations suggest a complex evolutionary history, with some species evolving unique features to thrive in various environments. Despite their interesting biology, apterygids went extinct at the end of the Permian period, likely due to the catastrophic Permian-Triassic extinction event.