Dryolestoidea

Dryolestoidea is an extinct clade of mesozoic mammals that only contains two orders. It has been suggested that this group contained the ancestors of modern therian mammals. They are mostly represented by teeth, fragmented dentaries and parts of the rostrum. The Jurassic forms retained a coronoid and splenial, but the Cretaceous forms lack these. Another primitive feature is the presence of a Meckelian groove (the Cretaceous forms have a reduced version).