What are Basal Amniotes?
Basal amniotes are the stem members of the amniote evolutionary tree. An amniote is a terrestrial tetrapod (four-legged animal) that reproduces by means of sophisticated eggs protected by several layers of embryos, including a hard shell, preventing them from drying out, and allowing them to lay their eggs in places other than water. Amniotes are the first animals that left wet, swampy regions and began colonizing continental interiors 340 million years ago. After just a few million years, basal amniotes diverged into synapsids (primitive relatives of mammals) and sauropsids (reptiles). These two groups are distinguished by the number of gaps they have in their skulls — synapsids have one gap behind each eye hole, while sauropsids have two. Anapsids (turtles, tortoises, and terrapins) have none, sparking debate about whether this group descended from sauropsids or if their common ancestor was among the basal amniotes. Basal amniotes evolved from reptiliomorphs, amphibians living approx
