Xenungulata

Xenungulata is an extinct order of hoofed mammals that lived in South America during the Paleocene and Eocene epochs. The name Xenungulata is derived from the Greek words "xenos" meaning strange and "onux" meaning hoof, and "glatos" meaning ungulate. These animals are known from fossil remains primarily found in the Itaboraí Basin of Brazil.

Members of Xenungulata were diverse in size, ranging from small to medium-sized mammals, with some species comparable to modern-day tapirs. They possessed distinctive dental and skeletal features that set them apart from other South American ungulate groups. Their molars were generally bunodont, meaning they had rounded cusps, suggesting a diet of soft vegetation.

The exact phylogenetic placement of Xenungulata has been a subject of debate among paleontologists. Initially, they were considered closely related to true ungulates (Artiodactyla and Perissodactyla), but later studies using more complete fossil evidence suggested they might represent an independent lineage that arose within South America. Some research has also linked them to other extinct South American mammals like Meridiungulata.

The extinction of Xenungulata is thought to have occurred by the end of the Eocene, possibly due to environmental changes or competition with other mammalian groups that arrived in South America later. Despite their limited fossil record and ongoing taxonomic discussions, Xenungulata provides important insights into the early evolution of mammals in the Neotropics.