👉 Pelycosaurians are a group of extinct mammals that lived during the Late Cretaceous period (about 100 million years ago to about 75 million years ago) in North America. They were known for their large, elongated heads and their ability to breathe through their nostrils using gills instead of lungs. Pelycosaurians are thought to have been herbivores that lived on land or in shallow water. The exact number of pelycosaurian
