Steropodon

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Steropodon
Temporal range:
Ma
Holotype mandible
Life reconstruction
of Steropodon
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Monotremata
Family: †Steropodontidae
Genus: †Steropodon
Archer, Flannery, Ritchie, & Molnar
, 1985
Species:
†S. galmani
Binomial name
†Steropodon galmani
Archer, Flannery, Ritchie, & Molnar
, 1985

Steropodon is a genus of prehistoric platypus-like monotreme, or egg-laying mammal. It contains a single species, Steropodon galmani, that lived about 105 to 93.3 million years ago (mya) during the Cretaceous period, from early to middle Cenomanian.[1] It is one of the oldest monotremes discovered, and is one of the oldest Australian mammal discoveries.

Taxonomy

Jaw on display at the American Museum of Natural History, New York City

The

evolved in the Jurassic, led to the conclusion that the molar evolved independently in the two lineages. This inspired the creation of the subclasses Australosphenida—the monotremes and extinct relatives—and Tribosphenida—placentals and marsupials. However, given this classification is based only on jaw and lower-tooth remains, insufficient evidence may exist to definitively make this conclusion.[2]

It may be only described member of the family Steropodontidae. Another proposed member is

stem ornithorhynchid.[3]

The specific epithet is derived from the surname of the jaw's collectors, when combined with the genus name Steropodon is intended to translate as "Galman's lightning tooth".[5]

Description

Model at the Australian Museum, Sydney

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.[6]

Woodburne (2003, p. 212) reports that the

Ornithorhynchus anatinus
.

See also

References

  1. ISSN 0311-5518
    .
  2. S2CID 6297739
    .
  3. ^
    S2CID 247542433
    .
  4. ISBN 9780643103153
    .
  5. ^ M. Archer, F. A. Jenkins, S. J. Hand, P. Murray, and H. Godthelp. 1992. Description of the skull and non-vestigial dentition of a Miocene platypus (Obdurodon dicksoni n. sp.) from Riversleigh, Australia, and the problem of monotreme origins. Platypus and Echidnas 15-27.
  6. S2CID 4342084
    .

Further reading

  • Mackness, Brian, Prehistoric Australia, Sydney, Golden Press, 1987.

External links
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