The skull (cranium and mandible) of AMNH 200255 was scanned by Matthew Colbert at the UTCT on 6 September 2000 (see the UTCT webpage for more details on the scanner). The middle and external ear ossicles (ectotympanic, stapes, incus, malleus) are also missing from the adult skull. ![]() The os paradoxum, a bone known only in Ornithorhynchus anatinus, is usually located at the dorsoanterior end of the vomers but is missing in AMNH 200255. The ectopterygoids are broken and mostly missing. There are also a number of bright objects visible on the slices (possibly buckshot) embedded in the turbinates (hor048-073). A fracture is visible on the CT slices that passes through the maxilla, ethmoid, and vomer (e.g., hor075). The skull (cranium and mandible) is completely articulated and is in good condition, with the keratinous grinding teeth plates intact, indicating that it was an adult at the time of death. There is no additional data accompanying the specimen. The loan for the specimen to Timothy Rowe was arranged with Dr. The skull of an adult Ornithorhynchus anatinus was obtained from the American Museum of Natural History (AMNH 200255) for scanning at The University of Texas High-Resolution X-ray Computed Tomography Facility (UTCT Facility) in Austin. Comparison of the CT images of the platypus specimens displayed on this site with other synapsids will undoubtedly reveal new morphological characters for phylogenetic analysis and help resolve the position of Monotremata within Mammalia.Ĭlick on the thumbnails below for labeled images of the juvenile and adult skulls in standard anatomical views. To remedy these problems, both adult and juvenile duckbill platypus skulls were scanned. Moreover, few studies are based on serial sectioning and concentrate on its internal cavities (Pritchard, 1881 Wilson and Hill, 1908 Watson, 1916 Zeller, 1989a, b) and these data have yet to be incorporated into systematic analysis. Morphological and some molecular data support the marsupial-placental clade, but some molecular studies support the monotreme-marsupial clade.Īlthough the osteology of Ornithorhynchus is well described (Pritchard, 1881 Wilson and Hill, 1908 Watson, 1916 de Beer and Fell, 1936 Simpson, 1938 Zeller, 1989a, b Musser and Archer, 1998), the literature is scattered and access to specimens is difficult. There is some debate as to whether monotremes are more closely related to marsupials, or if marsupials and placentals are more closely related to each other. Other notable specimens include a 62 million year old tooth (Paleocene) from South America (Pascual et al., 1992), and a nearly complete skull of an extinct platypus ( Obdurodon dicksoni) from the Miocene (15 million years old) of Australia (Archer et al., 1992 Musser and Archer, 1998). The oldest known specimen is a jaw fragment with teeth from the Cretaceous (110 million years old) of Australia (Archer et al., 1985). ![]() The fossil record for monotremes is poor, with few well preserved specimens. It is now known that the platypus, along with the Australasian echidnas ( Tachyglossus and Zaglossus),Ĭomprise the living members of Monotremata, the egg-laying mammals, all of which have a single, common opening for the reproductive, excretory, and digestive systems. In addition, the males have a single spur on each hind ankle that contains venom, and the females lay eggs (Grant, 1995). It has a beak like a duck, webbed forelimbs for swimming, clawed hind feet for aid in burrowing, a common opening for the reproductive, excretory and digestive systems, and a broad, flat tail. This bizzare animal is about the size of a house cat and is covered by thick waterproof hair. It is not difficult to understand why early European explorers were initially puzzled with the classification of the platypus. Ornithorhynchus anatinus, the duckbill platypus, is a unique mammal native to Queensland, New South Wales, Victoria, South Australia, and Tasmania, where it frequents freshwater streams, rivers, lakes, and lagoons.
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