More than just “echidnapus”

Image by Peter Schouten, illustrating the various new monotremes.

A recent study has found three new monotreme species and a revision of other monotremes from the Cenomanian of Australia. Media has just looked at this and focused on the “echidnapus” (Opalios splendens), but in truth this paper offers a very unique take: in the Late Cretaceous (or at least during the Cenomanian), monotremes were the only mammals in Australia, or at least the most diverse. This contrasts with early Cretaceous sites which include multituberculates (i.e. Correibaatar marywaltersae) and early therians, and obviously with Cenozoic Australian faunas dominated by marsupials.

This, combined with the dominance of dryolestoids in Cretaceous South America and therians in India, seems to suggest that Late Cretaceous Gondwanna had mammal faunal provincialism, with only a few clades being widespread (gondwanatherians, some therians and the south american monotremes). Since we don’t have Australian Maastrichtian or Paleocene fossil reccord, it’s unclear if this monotreme diversity survived the KP extinction even ot did and were later supplanted by marsupials (leaning more towards the former)

Overall an excellent paper and one that contributes to our understand of Cretaceous Australia.