Obdurodon

The Obdurodon insignis holotype specimen, SAM P18087, a tooth, was uncovered in 1971 from the Etadunna Formation in the Tirari Desert of South Australia. The second specimen discovered there, AMNH 97228, is an upper right molar. The holotype tooth was placed into the newly erected genus Obdurodon upon description in 1975 by American palaeontologists Michael O. Woodburne and Richard H. Tedford. They named the genus from the Latin obduro "persist" and the Greek ὀδών (odṓn) "tooth", in reference to the permanency of the molars, The species name insignis "remarkable" refers to the importance of the new taxon's "distinguishing mark" in the fossil record. The second species named, Obdurodon dicksoni, occasionally called the Riversleigh Platypus, was described by Archer et al (1992) who detailed a skull and several teeth found in lower-middle Miocene deposits from the Riversleigh Ringtail Site. The type specimen, an exceptionally well preserved skull, is one of the most intact fossil skulls to be excavated from Riversleigh. The type locality is referred to as the Ringtail Site. Other than the skull and teeth, no other fossilized material of O. dicksoni has been identified. The holotype tooth was discovered in 2012 at the "Two Trees Site", The species was described the following year by a team from the University of New South Wales including Rebecca Pian, Mike Archer, and Suzanne Hand, who published the article in the Journal of Vertebrate Paleontology. The specific name was chosen in honour of an indigenous Australian creation story for the platypus, where a duck named Tharalkoo gives birth to a chimeric creature after being ravished by a rakali. ==Description==

Obdurodon differed from the modern platypus in that they had more permanent dentition in the spoon-shaped bill, retaining molars and incisors. Obdurodon insignis O. insignis is thought to have had a similar build to the modern platypus. The holotype is the front molar of the upper right jaw, corresponding to the M2 molar, with the unusual character of six roots. Obdurodon dicksoni Obdurodon dicksoni was part of the Riversleigh fauna that inhabited pools and streams of freshwater of the Riversleigh rainforest environment. Unlike the modern species, O. dicksoni was a large animal that retained its molars into adulthood and had a spoon-shaped bill. The skull's profile is comparatively flatter than similar species, and as with crocodilians, this may indicate more foraging or feeding at the surface of the water. The diet is likely to have been crustaceans, the water-borne larvae of insects, or perhaps small vertebrates like fish and frogs. The only known area of its distribution, the Riversleigh site, was closed forest at the freshwater bodies it inhabited, surrounded by more open woodlands over the region's limestone karst terrain. Obdurodon tharalkooschild Obdurodon tharalkooschild is assumed to be very similar in form to a modern platypus, but larger, exceeding Monotrematum in size and length at . and lived in the middle to late Miocene (). The wear patterns on the tooth are suggestive of crushing, perhaps by consuming hard-shelled animals such as turtles, rather than using a shearing action. O. tharalkooschild is thought to have inhabited fresh water and hunted for a variety of animal prey in the forests that dominated the Riversleigh site at the time of deposition. The species diet is assumed to have included crustacea like those consumed by the modern platypus, although larger species were available due to its greater size. The potential prey of the Riversleigh fauna also included frog, turtle, fish and the lungfish, species that are present in the deposition at the Two Tree Site of the Riversleigh formations. The ornithorhynchid species were unknown in the later fossil record at the time of discovery, and it defied the assumptions of a single lineage of a platypus-like animal that progressively lost its teeth and became smaller. ==Cultural references==

The name given to O. tharalkooschild was first discussed in a 1990 paper by Mike Archer, an Australian mammalogist, detailing a creation story with an Ugly Duckling motif in the context of palaeontology. An illustration of O. dicksoni by Jeanette Muirhead, depicted on a rock in a stream within a rainforest, was published by the magazine Natural History (AMNH) in 1994. == References ==