Name: Steropodon ‭(‬Lightning tooth‭)‬.
Phonetic: Steh-roe-poe-don.
Named By: Archer,‭ ‬Flannery,‭ ‬Ritchie,‭ & ‬Molnar‭ ‬-‭ ‬1985.
Classification: Chordata,‭ ‬Mammalia,‭ ‬Monotremata,‭ ‬Platypoda,‭ ‬Steropodontidae.
Species: S.‭ ‬glamani‭ (‬type‭)‬.
Diet: Carnivore.
Size: Estimated between‭ ‬40-50‭ ‬centimetres long.
Known locations: Australia,‭ ‬New South Wales,‭ ‬Lightning Ridge‭ ‬-‭ ‬Griman Creek Formation.
Time period: Mid Albian of the Cretaceous.
Fossil representation: Single opalised right mandible with‭ ‬3‭ ‬molar teeth.

       Before the description of Teinolophos in‭ ‬1999,‭ ‬Steropodon was considered to be the earliest ancestor of the platypus.‭ ‬Comparison to mammals like the platypus has yielded body estimates of around forty to fifty centimetres long,‭ ‬something that would make Steropodon one of the larger known mammals of the early Cretaceous period.‭ ‬If Steropodon lived like a modern day platypus then it likely hunted in water like them too.‭ ‬Also by staying close to water,‭ ‬Steropodon may have been able to avoid the large theropod dinosaurs like Australovenator that were in Australia at this time.‭ ‬The bad news however is that by living in around water it may have come into contact with Cretaceous era crocodiles like Isisfordia.
       As often happens with Australian fossils,‭ ‬the jaw bone of Steropodon has been turned to opal.‭ ‬Another monotreme mammal that is also named from the same location and from only an‭ ‬opalised jaw is Kollikodon.‭ ‬This process of opalisation has also happened to fossils of the dinosaurs Kakuru,‭ ‬Rapator and Walgettosuchus.

Further reading
- First Mesozoic mammal from Australia - an early Cretaceous monotreme. - Nature 318:363-366. - M. Archer, T. F. Flannery, A. Ritchie & R. E. Molnar - 1985.


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