Steropodon galmani was a prehistoric monotreme, or egg-laying mammal species that lived during the middle Albian stage, in the Lower Cretaceous period. It is the earliest known platypus-like creature. The conservation status of a species is an indicator of the likelihood of that species continuing to survive. ... Scientific classification or biological classification is how biologists group and categorize extinct and living species of organisms. ... Phyla Porifera (sponges) Ctenophora (comb jellies) Cnidaria Placozoa Bilateria Acoelomorpha Orthonectida Rhombozoa Myxozoa Superphylum Deuterostomia    Chordata (vertebrates, etc. ... Typical Classes Subphylum Urochordata - Tunicates Ascidiacea Thaliacea Larvacea Subphylum Cephalochordata - Lancelets Subphylum Myxini - Hagfishes Subphylum Vertebrata - Vertebrates Petromyzontida - Lampreys Placodermi (extinct) Chondrichthyes - Cartilaginous fishes Acanthodii (extinct) Actinopterygii - Ray-finned fishes Actinistia - Coelacanths Dipnoi - Lungfishes Amphibia - Amphibians Reptilia - Reptiles Aves - Birds Mammalia - Mammals Chordates (phylum Chordata) include the vertebrates, together with... Orders Subclass Monotremata Monotremata Subclass Marsupialia Didelphimorphia Paucituberculata Microbiotheria Dasyuromorphia Peramelemorphia Notoryctemorphia Diprotodontia Subclass Placentalia Xenarthra Dermoptera Desmostylia Scandentia Primates Rodentia Lagomorpha Insectivora Chiroptera Pholidota Carnivora Perissodactyla Artiodactyla Cetacea Afrosoricida Macroscelidea Tubulidentata Hyracoidea Proboscidea Sirenia The mammals are the class of vertebrate animals primarily characterized by the presence of mammary... Families Kollikodontidae (extinct) Ornithorhynchidae - Platypus Tachyglossidae - Echidnas Steropodontidae (extinct) Monotremes (< monos, single + trema, hole; refers to the cloaca) are mammals that are best known for laying eggs, instead of giving birth to live young like marsupials and placental mammals (Eutheria). ... In biology, binomial nomenclature is a standard convention used for naming species. ... 1985 is a common year starting on Tuesday of the Gregorian calendar. ... Families Kollikodontidae (extinct) Ornithorhynchidae - Platypus Tachyglossidae - Echidnas Steropodontidae (extinct) Monotremes (< monos, single + trema, hole; refers to the cloaca) are mammals that are best known for laying eggs, instead of giving birth to live young like marsupials and placental mammals (Eutheria). ... Orders Subclass Monotremata Monotremata Subclass Marsupialia Didelphimorphia Paucituberculata Microbiotheria Dasyuromorphia Peramelemorphia Notoryctemorphia Diprotodontia Subclass Placentalia Xenarthra Dermoptera Desmostylia Scandentia Primates Rodentia Lagomorpha Insectivora Chiroptera Pholidota Carnivora Perissodactyla Artiodactyla Cetacea Afrosoricida Macroscelidea Tubulidentata Hyracoidea Proboscidea Sirenia The mammals are the class of vertebrate animals primarily characterized by the presence of mammary... In biology, a species is a kind of organism. ... The Cretaceous period is one of the major divisions of the geologic timescale, reaching from the end of the Jurassic period (about 135 mya) to the beginning of the Paleocene epoch of the Tertiary period (65 mya). ... Binomial name Ornithorhynchus anatinus Shaw, 1799 The platypus (Ornithorhynchus anatinus) is a small, semi-aquatic mammal endemic to the eastern part of Australia, and one of the four extant monotremes, the only mammals that lay eggs instead of giving birth to live young (the other three are echidnas). ...

Steropodon is known only from a single opalised jaw with three molars, discovered at the Griman Creek Formation, Lightning Ridge, New South Wales, Australia. It was a large mammal for the Mesozoic, being 40 - 50cm long. The lower molars are 5 - 7mm in length, with a width of 3 - 4mm. A length of 1 - 2mm is more typical for Mesozoic mammals. Also from Lightning Ridge is Kollikodon ritchiei. OPAL is also the name of one of the four detectors of the Large Electron-Positron Collider. ... For other uses of the word jaws, see jaws (disambiguation). ... A molar is the fourth kind of tooth in mammals. ... Lightning Ridge is a town of approximately 2000 persons in north-western New South Wales, Australia. ... Motto: Orta Recens Quam Pura Nites (Newly Risen, How Brightly You Shine) Nickname: Premier State Other Australian states and territories Capital Sydney Government Governor Premier Const. ... Orders Subclass Monotremata Monotremata Subclass Marsupialia Didelphimorphia Paucituberculata Microbiotheria Dasyuromorphia Peramelemorphia Notoryctemorphia Diprotodontia Subclass Placentalia Xenarthra Dermoptera Desmostylia Scandentia Primates Rodentia Lagomorpha Insectivora Chiroptera Pholidota Carnivora Perissodactyla Artiodactyla Cetacea Afrosoricida Macroscelidea Tubulidentata Hyracoidea Proboscidea Sirenia The mammals are the class of vertebrate animals primarily characterized by the presence of mammary... The Mesozoic is one of three geologic eras of Phanerozoic eon. ... Kollikodon is an extinct species of Monotreme. ...

The molars "bear striking resemblance to the tribosphenic pattern characteristic of living therians..." (Pascual). However, there are also differences: there is no entoconid, and an absence of wear seems to suggest that the upper molars (as yet unknown) did not have a protocone. The molar design that is considered one of the most important characteristics of mammals is a three-cusped shape called a tribosphenic molar. ...

Woodburne (2003, p.212) reports that the holotype is a right mandible named AM F66763, which seems to work at the Australian Museum, Sydney. The preserved molars are m1 - m3. Page 237 includes: "In Steropodon, the madibular canal suggests the presence of a bill, with a bill also known in Obdurodon dicksoni and Ornithorhynchus anatinus." A holotype (sometimes simply type) is the single physical example or illustration of an organism that defines the characteristics of the whole species. ... Sydneys skyline with the Opera House on the left Sydney is the capital city of the Australian state of New South Wales and Australias largest and oldest city, founded in 1788. ... Species Obdurodon dicksoni Obdurodon insignis Monotrematum sudamericanum Obdurodon is an extinct genus of platypus containing three species. ... Binomial name Ornithorhynchus anatinus Shaw, 1799 The platypus (Ornithorhynchus anatinus) is a small, semi-aquatic mammal endemic to the eastern part of Australia, and one of the four extant monotremes, the only mammals that lay eggs instead of giving birth to live young (the other three are echidnas). ...

See also

• Fossil monotremes

Families Kollikodontidae (extinct) Ornithorhynchidae - Platypus Tachyglossidae - Echidnas Steropodontidae (extinct) Monotremes (< monos, single + trema, hole; refers to the cloaca) are mammals that are best known for laying eggs, instead of giving birth to live young like marsupials and placental mammals (Eutheria). ...

External links

• BBC, Walking With Dinosaurs (http://www.bbc.co.uk/dinosaurs/fact_files/forest/birds_mammals/steropodon.shtml)
• Australia’s Lost Kingdoms (http://www.lostkingdoms.com/facts/factsheet8.htm)
• Lost Sea Opals (http://www.lostseaopals.com.au/fossils/index.asp) An array of fossils from the Lightning Ridge location. Many animal groups are represented.

References

• Archer, M., Flannery, T.F., Ritchie, A., Molnar, R.E. (1985). "First Mesozoic mammal from Australia — an early Cretaceous monotreme". Nature 318: 363-366.