eureptilian

Eureptilia is a clade of diapsid reptiles that includes all living reptiles (including birds) and their closest extinct relatives. The term is derived from the Greek words "eu" meaning "true" and "reptilia" meaning "reptile". Eureptilia is characterized by the presence of two temporal fenestrae in the skull, a pair of openings behind the eye socket. This diapsid condition is a key feature that distinguishes eureptilians from other reptile groups like anapsids (which lack temporal fenestrae) and synapsids (which have a single temporal fenestre).

The eureptilian lineage originated during the Late Carboniferous period, approximately 310 million years ago. Early eureptilians were small, lizard-like creatures. Over time, this group diversified into a vast array of forms, adapting to numerous ecological niches. This diversification led to the evolution of major reptile groups such as turtles, lizards, snakes, crocodilians, and dinosaurs. Birds, scientifically classified as avian dinosaurs, are also considered members of the eureptilian clade, representing a surviving lineage of theropod dinosaurs.

Key evolutionary developments within Eureptilia include the evolution of flight in pterosaurs and birds, the development of endothermy (warm-bloodedness) in birds and some extinct dinosaur lineages, and the evolution of diverse feeding strategies and reproductive methods. The fossil record provides extensive evidence for the evolutionary history and diversification of eureptilians, making them a crucial group for understanding vertebrate evolution.