Thelodonts

Thelodonts are a group of extinct mammals that lived during the Paleogene period, approximately 66 to 23 million years ago. They are known for their distinctive teeth, which are characterized by a single, large, conical tooth in the upper jaw and a corresponding tooth in the lower jaw. This unique dental structure is often referred to as the "thelodont" condition, from which the group derives its name. Thelodonts are believed to have been insectivorous, feeding on a diet of insects and other small invertebrates.

Thelodonts are classified within the order Insectivora, which also includes modern-day insectivores such as shrews and hedgehogs. They are further divided into two suborders: Paenungulata and Scandentia. Paenungulata includes the earliest thelodonts, which had a more primitive dental structure, while Scandentia includes the more advanced thelodonts, which had a more specialized dental structure.

Thelodonts are known from fossils found in North America, Europe, and Asia. They are thought to have evolved from earlier insectivores and to have played an important role in the evolution of modern-day insectivores. However, their exact relationships with other insectivores remain a topic of ongoing research.