Recent fossil discoveries from the Namba Formation in South Australia have revealed that 25 million years ago, Obdurodon’s insignis — an ancient, larger, toothed ancestor of the modern platypus (Ornithorhynchus anatinus) — thrived alongside freshwater dolphins and other now-extinct species in verdant inland lakes.
An artist’s impression of the approximately 25-million-year-old fossil platypus and its surroundings. Image credit: Gen Conway, Flinders University Institute of Paleontology
“The platypus is extremely rare in the fossil record, mostly limited to tooth remains, making the discovery of new fossils significant for understanding this unique mammal,” stated Flinders University palaeontologist Dr. Aaron Camens.
First described in 1975, Obdurodon’s insignis inhabited the vast permanent lakes, slow-flowing rivers, and forested lowlands of central Australia during the late Oligocene, approximately 25 million years ago.
This species notably differs from today’s platypuses, possessing fully formed molars and premolars, unlike modern platypuses, which lose their vestigial teeth shortly after hatching.
Previously, Obdurodon’s insignis was known only from limited remains, including one and a half molars and fragments of the jaw and pelvis. However, this recent find includes one of the few well-preserved fossils of a related younger species, Obdurodon dicksoni, identified in 1992.
While Obdurodon dicksoni resembled modern platypuses, it had a slightly larger skull and a stronger bite.
“The new material of Obdurodon’s insignis includes the first premolars, the key teeth located in front of the molars,” said Dr. Camens. “This species had large, pointed front teeth and formidable molars capable of crushing shelled animals, such as yabbies.”
Dr. Trevor Worthy, also from Flinders University, highlighted an intriguing discovery: the scapulochoroid bone, which supports the arms and forelimbs. “This finding indicates that the limb structure closely resembles that of modern platypuses, suggesting ancient platypuses were adept swimmers like their modern relatives,” he noted.
“These fossils, dating back 25 million years, provide a glimpse of an ancient platypus that was larger and possessed teeth compared to modern variants.”
Research indicates that during this period, dense forests nurtured diverse communities of arboreal mammals, including koalas and various possum species.
On the forest floor, a sheep-sized marsupial coexisted with numerous other species, including familiar lizards, frogs, and small carnivorous marsupials.
These ancient trees also hosted a variety of birds, including the impressive Steller’s sea eagle, Archehieracus.
The ancient lakes teemed with lungfish and other small fish, while several species of waterfowl, cormorants, and flamingos thrived along the shores, feeding on fish, plants, and small invertebrates.
Interestingly, these freshwater ecosystems were also home to small dolphins, with their teeth and bones discovered at several fossil locations, revealing signs of this diverse ancient community.
“This rich environment was where the ancient toothed platypus lived 25 million years ago, before its remains settled into the lake’s depths,” explained Dr. Jen Conway, also from Flinders University.
This remarkable discovery is detailed in the latest issue of Australian Zoologist.
_____
Trevor H. Worthy et al. 2026. New material for the toothed platypus Obdurodon’s insignis (Monotremata: Ornithorhynchidae) from the Late Oligocene fauna of Pimpa, Billeroo Creek, South Australia. Australian Zoologist 45 (1): AZ26011; doi: 10.1071/AZ26011
Source: www.sci.news
