Cimolodonta

Cimolodonta is an extinct order of placental mammals that lived during the Late Cretaceous period. Fossils attributed to this order have been found in North America and Asia. Cimolodonts are characterized by their hypsodont teeth, meaning they had high-crowned teeth adapted for grinding tough vegetation. This dental adaptation suggests a herbivorous or omnivorous diet.

The taxonomic placement of Cimolodonta has been a subject of debate among paleontologists. Historically, they were often grouped with multituberculates, an ancient order of mammals that coexisted with dinosaurs. However, more recent phylogenetic analyses, based on both morphological and molecular data, have placed Cimolodonta within the placental mammals. This reclassification has significant implications for understanding the early evolution and diversification of placental mammals.

Key genera within Cimolodonta include Cimolodon and Mesungulatum. These mammals were generally small to medium-sized, with some species reaching the size of a large rodent. Their skeletal features suggest they were terrestrial and likely lived in open or semi-open environments. The extinction of Cimolodonta occurred at the end of the Cretaceous period, likely as part of the mass extinction event that wiped out the non-avian dinosaurs. Their disappearance paved the way for the diversification of other mammalian groups in the subsequent Paleogene period.