Steropodon
Steropodon
Steropodon galmani is an extinct mammal. She lived in the Cretaceous period in Australia and one of the earliest known ancestor of the platypus.
Features
The fossils are restricted to parts of the lower jaw and several molars that were discovered in the form of opal in New South Wales. The molars were approximately 5-7 mm long and 3-4 mm wide. Noteworthy are the three cusps of the molars, which are reminiscent of the teeth of some tribosphenic Higher mammals. Otherwise, little is known about Steropodon. Based on the length of the jaw members found the body length is estimated to be around 40 to 50 centimeters. This would be smaller than in the living in the same region Kollikodon, but for Mesozoic mammals is still very large.
System
Steropodon applies not only Teinolophos as one of the earliest known representatives of Ornithorhynchidae that are still represented by the platypus. The similarities between the teeth of these and related species with those of other Mesozoic mammals from Gondwana has raised new discussion on the descent relations of Ursäuger to the other groups of mammals. See Nomenclature of Ursäuger.