Captorhinidliks

Captorhinidliks are an extinct group of reptiles belonging to the order Captorhinida. They are considered to be among the earliest known reptiles, appearing in the late Pennsylvanian period, around 300 million years ago, and persisting into the Permian period. Captorhinidliks are important for understanding the early evolution of reptiles and their transition from an amphibian ancestry.

These ancient creatures were generally small to medium-sized, with most species ranging from a few inches to about a meter in length. They possessed a robust build with a short tail and a broad skull. A distinctive characteristic of many captorhinidliks was the presence of multiple rows of small, peg-like teeth on both the upper and lower jaws, suggesting a diet of insects, small invertebrates, or possibly plants. Some species, like Captorhinus, had up to five rows of teeth.

The fossil record of captorhinidliks is primarily found in North America and Europe. Their skeletal features, such as the presence of a temporal fenestra (an opening in the skull behind the eye socket) and a reduced number of bones in the skull compared to their amphibian ancestors, mark them as early amniotes, the group that includes all reptiles, birds, and mammals. The exact phylogenetic position of Captorhinida within Amniota is still a subject of scientific debate, with some studies placing them as basal members of the eureptilian lineage, while others suggest they represent an early offshoot or even a sister group to all other amniotes. Their extinction occurred by the end of the Permian period, alongside many other reptile groups, due to the devastating Permian-Triassic extinction event.