👉 Scienids are a group of extinct reptiles that lived during the Late Cretaceous period in North America. They were characterized by large, elongated bodies with sharp, pointed teeth and a long neck. Scienids were known for their distinctive shell patterns, which included a series of large, circular depressions on each side of the shell. The shells of scienids were often made from a combination of calcium carbonate and silicate minerals, which allowed them to retain moisture in difficult conditions