Xenungulidae

Xenungulidae is a small family of extinct mammals that lived during the Paleocene epoch. The name Xenungulidae means "strange hoofed ones" in reference to their unusual foot structure. These animals are known only from fossilized teeth and jaw fragments found in North America and Europe. Xenungulidae are considered to be among the earliest known ungulates, or hoofed mammals, and their discovery has provided valuable insights into the early evolution of this important group.

The defining characteristic of Xenungulidae is their unique dentition, particularly the shape and arrangement of their molar teeth. These teeth suggest a diet of tough plant material, indicating that Xenungulidae were likely herbivores. Their locomotion is less understood due to the limited fossil record, but the name implies some form of hoof-like structures on their feet. The exact evolutionary relationships of Xenungulidae to other ungulate groups are still debated by paleontologists, with some placing them as a basal lineage and others suggesting a closer connection to specific modern ungulate orders. The limited fossil evidence makes it challenging to reconstruct their full anatomy and ecology. The extinction of Xenungulidae likely occurred before the Eocene, with their ecological niche potentially being filled by more derived and successful ungulate groups that emerged later.