Orthotilians

Orthotilians are a group of extinct mammals that lived during the Paleogene period, approximately 66 to 23 million years ago. They are characterized by their straight, non-retractile claws, which is reflected in their name, derived from the Greek words "orthos" meaning straight, and "tilos" meaning claw. Orthotilians are believed to have been the ancestors of modern ungulates, such as horses, deer, and cattle.

The earliest known orthotilians appeared in North America during the Paleocene epoch. They were small, insectivorous creatures, similar to modern-day shrews. Over time, orthotilians evolved to become larger and more specialized, with some species developing adaptations for grazing on grasses and other plants.

Orthotilians are known from fossils found in North America, Europe, and Asia. They are classified into several families, including Hyopsodontidae, Mesohippidae, and Merycoidodontidae. The most well-known orthotilian is the hyopsodont, a large, herbivorous mammal that lived during the Eocene epoch.

Despite their importance in the evolution of modern ungulates, orthotilians are not well-represented in the fossil record. This is likely due to their small size and the fact that they were not well-adapted for fossilization. However, ongoing research continues to shed light on the diversity and evolution of these fascinating mammals.