- Six monotreme species coexisted at Lightning Ridge 100 million years ago.
- Opalios splendens blended platypus and echidna traits, earning the nickname "echidnapus."
- The find adds more than 20% to all previously known monotreme diversity.
Six species of monotremes - egg-laying mammals like the platypus and echidna - lived in the same place at the same time, 100 million years ago. The fossils, opalised jaws found at Lightning Ridge in New South Wales, rewrite what we thought we knew about these animals.
What is a monotreme?
Monotremes are the only mammals that lay eggs instead of giving birth to live young. Unlike all other mammals, they reproduce by laying leathery eggs, yet still nurse their hatchlings with milk. Today only five species survive: the platypus and four echidna species, all found in Australia and New Guinea.
Key figure
+20%
Added to previously known monotreme diversity by the Lightning Ridge discovery
"It's like discovering a whole new civilisation," said Professor Tim Flannery, Honorary Associate of the Australian Museum.
The Echidnapus
One of the newly described species, Opalios splendens, sits at a curious point in the evolutionary tree. Its anatomy resembles a platypus, but its jaw and snout look more like an echidna.
"You might call it an 'echidnapus,'" said Professor Kris Helgen, Chief Scientist at the Australian Museum Research Institute.
Opalios splendens still had five molars. Modern echidnas have no teeth at all. Modern platypuses lose theirs before adulthood.
The evolution of monotremes, it turns out, is a story of toothy to toothless.
Stirtodon and the Others
The six species range from tiny to cat-sized. Stirtodon elizabethae was the largest monotreme of its era. Parvopalus clytiei was the smallest. Kollikodon ritchiei had molars shaped like hot cross buns. Dharragarra aurora is the earliest known platypus species.
All of them lived in what is now Lightning Ridge during the Cenomanian Age of the Cretaceous Period, between 102 and 96 million years ago.
The fossils were found by Elizabeth Smith and her daughter Clytie of the Australian Opal Centre, who spent decades searching the opal fields.
Before Marsupials
The discovery, published in Alcheringa: An Australasian Journal of Palaeontology, adds more than 20 percent to the previously known diversity of monotremes.
No other mammal fossils have been found from this period at Lightning Ridge. The monotremes, it seems, had Australia to themselves - alongside the dinosaurs.
...before Australia became the land of pouched mammals, this was a land of furry egg-layers
Elizabeth Smith, fossil hunter
"These specimens show the world that long before Australia became the land of pouched mammals, this was a land of furry egg-layers," said Elizabeth Smith.
Today, only two monotreme lineages survive: the platypus and the four species of echidna. The opalised jaws from Lightning Ridge suggest their ancestors were far more varied, and far more numerous, than anyone expected.
Fact Check: Claim-by-Claim Verification Verified
The recap accurately represents the source article's claims, quotes, species names, ages, and scientific details from the Alcheringa paper.
Commentary
- Source age range is precisely 102-96.6 Ma; article's "102 and 96 million years ago" is a minor rounding acceptable for popular recap.
- Three new genera described (Opalios, Dharragarra, Parvopalus); other three previously known, totaling six species confirmed.
Sources used for verification
Fact-checked by Perplexity Sonar Pro on 2025-12-18
