Taeniodonta
Taeniodonta is an extinct early group of cimolestid mammals known from the Palaeocene to the Eocene. Taeniodonts evolved quickly into highly specialized digging animals, and varied greatly in size, from rat-sized to species as large as a bear. Later species developed prominent front teeth and huge claws for digging and rooting. Some genera, like Stylinodon, had ever-growing teeth.
Two families belong to this group, Stylinodontidae and Conoryctidae. They were endemic to North America. The scarcity of taeniodont fossils can be explained by the fact that these animals probably lived in dry or arid climates unconductive to fossilization. Taeniodonts are unambiguously Eutherians, and part of Cimolesta; Cimolestes is the immediate outgroup to Taeniodonta.From Thomas E. Williamson and Stephen L. Brusatte :
