page_title: Steropodon
section_title: Description
hierarchical_section_title: Steropodon / Description
caption_attribution_description: English: Steropodon jaw on public display at the American Museum of Natural History, New York city, I clicked this image with my digital camera.
context_page_description: Steropodon galmani is a prehistoric species of monotreme, or egg-laying mammal, that lived about 105 million years ago in the Late Cretaceous period. It is one of the oldest monotremes discovered, and is one of the oldest Australian mammal discoveries.
context_section_description: Steropodon is known only from a single opalised jaw with three molars, discovered at the Griman Creek Formation, Lightning Ridge, New South Wales, Australia, by brothers David and Alan Galman. It was a large mammal for the Mesozoic, being 40–50 centimetres (16–20 in) long. The lower molars are 5–7 millimetres (0.20–0.28 in) in length, with a width of 3–4 millimetres (0.12–0.16 in). A length of 1–2 centimetres (0.39–0.79 in) is more typical for Mesozoic mammals.
  Woodburne (2003, p. 212) reports that the holotype is a right mandible named AM F66763. The preserved molars are m1–m3. Examination of the jaw fragment revealed a mandibular canal, which has been proposed to indicate the presence of a bill, similar to those of the extinct species Obdurodon dicksoni and the modern platypus Ornithorhynchus anatinus.
caption: The Steropodon jaw on display at the American Museum of Natural History, New York City, USA
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