Obdurodon is a genus of extinct platypus-like Australian monotreme which lived from the Late Oligocene to the Late Miocene. Three species have been described in the genus, the type species Obdurodon insignis, plus Obdurodon dicksoni and Obdurodon tharalkooschild. The species appeared much like their modern day relative the platypus, except adults retained their molar teeth, and Unlike the platypus which forages on the lakebed, they may have foraged in the water column or surface.
The Obdurodon insignis holotype specimen, SAM P18087, a tooth, was uncovered in 1971 from the Etadunna Formation in the Tirari Desert of South Australia.[1][2] The second specimen discovered there, AMNH 97228, is an upper right molar.[1] In total, 4 specimens are reported, dating from the Oligocene to the Pliocene.[3]
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 coined the genus named from the Latin obduros, meaning "persistent", and don, meaning "tooth" in reference to the permanency of the molars,[1] a feature which is lost in the modern platypus.[4] The species name insignis refers to the importance of the new taxon's "distinguishing mark" in the fossil record.[1]
The genus is one of several to have been placed with the family Ornithorhynchidae, whose only living member is the platypus.[5]
The second species named, Obdurodon dicksoni, occasionally called the Riversleigh Platypus,[6] 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.[6]
The third known species, Obdurodon tharalkooschild is the second species described from the Riversleigh sites, and the largest species.[7][8] The holotype tooth was discovered in 2012 at the "Two Trees Site",[5] part of Riversleigh's Gag Plateau sequence, and dated to the Miocene 4.4 million years ago though dates as young as the Pliocene have been suggested.[9] 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.[10][11]