Ptyctodontinae

Ptyctodontinae is a subfamily of extinct mammals that lived during the Eocene epoch, approximately 56 to 34 million years ago. They are known for their distinctive, flattened skulls and robust dentition, which suggests they were herbivorous. Ptyctodonts are believed to have been semi-aquatic, with their flat skulls and short limbs adapted for a semi-aquatic lifestyle. They are found in North America, Europe, and Asia, with the most diverse and abundant fossil record in North America. The subfamily includes several genera, such as Ptyctodus, Purgatorius, and Purgatoriodus. Ptyctodonts are considered to be a sister group to the modern order Artiodactyla, which includes even-toed ungulates such as pigs, hippos, and deer. The extinction of Ptyctodontinae is thought to have been caused by a combination of factors, including climate change and competition with other herbivorous mammals.