As regards the affinities of the creatures to which these jaws belonged, Professor Osborn has referred the Triconodontidae and Amphitheriidae, together with the Curtodontidae (as represented by the English Purbeck Curtodon), to a primitive group of marsupials, while he has assigned the Amblotheriidae and Stylacodontidae to an ancestral assemblage of Insectivora.
Of the Insectivora numerous forms of moles, shrews and hedgehogs prevail.
Amongst the Insectivora very peculiar forms are found, such as Gymnura and Tupaia.
The same conclusion is indicated by the absence from the Moluccas and Celebes of various other Mammals, Quadrumana, Carnivora, Insectivora and Ruminants, which abound in the western part of the Archipelago.
Among the Insectivora, the alpine shrew (Sorex alpinus) is restricted to the Alps.