Published: Sunday, May 26, 2024
Credit: Peter Shouten
A team of Australian scientists from the Australian Museum, Museums Victoria and Australian Opal Centre published today an article in Alcheringa: The Australasian Journal of Palaeontology that reveals evidence of a “Eage of Monotremes”.
Two mammalogists led the findings: Professor Tim Flannery, Honorary Associate at the Australian Museum and Professor Kris Helgen Chief Scientist and Director, Australian Museum Research Institute.
The opalized teeth found in Lightning Ridge, NSW, date back to between 102 and 96.6 millions years ago, during the Cretaceous Period.
Professor Flannery stated that the research revealed that Australia had a variety of monotremes 100 million years ago. The platypus, and echidna, are the only descendants.
“Today Australia is known for being a land of mammals, but these fossils are the first evidence that Australia once had a diverse population of monotremes.” Professor Flannery says it’s “like discovering a new civilization”.
Professor Helgen is the Director and Chief Scientist of the Australian Museum Research Institute. He said that the three new monotremes display combinations of features never seen in any other fossil or living monotremes. Opalios magnifens is one of the most striking monotremes. It retains features of the oldest known monotremes but also foreshadows adaptations seen in living monotremes such as the platypus and echidnas.
“Opalios magnifens occupies a position in the evolutionary tree that is prior to the evolution the common ancestor for the monotremes of today. Its overall anatomy is similar to that of a platypus. However, the features on the jaw and the snout are more similar to those of an echidna. You might even call it an “echidnapus,” said Professor Helgen.
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The oldest monotreme Teinolophos, which dates back 130 million years, tells the story of our evolution from toothy to toothless. We see that some monotremes had five molars 100 million years ago but others only have three, Professor Helgen explained.
Professor Flannery pointed out that today’s echidnas and platypuses are toothless.
“Adults platypus do not have teeth. Juveniles have primitive molars. We think we’ve solved the mystery of why and when adult platypus stopped having teeth after almost 100 million years. The competition between the Australian water rats, who arrived in Australia only 2 million years ago, may have caused the platypuses to search for softer and slipperier foods that were best processed using the leathery pads used by adults today”, Professor Flannery explained.
Paleontologist Tim Flannery holds a tooth fragment that is estimated to be 100 million years old. The image was taken at the Australian Museum, Sydney where the majority of the academic research on the discovery took place. May 22, 2024. Photo credit: James Alcock/Australian Museum
The story of this unique Australian tale is the fact that we can see in a single snapshot six different egg-laying mammal species living together at Lightning Ridge more than 100 million years ago. They all have potential evolutionary fates that could go in different directions. And they are all distant relatives and ancestors of the monotremes we see today.
The discovery of three monotremes genera by Dr. Matthew McCurry of the Australian Museum’s Palaeontology Department helps piece together their evolutionary story.
The Cenomanian Lightning Ridge assemblage of New South Wales contains six monotremes species, including three that are newly described. This is the most diverse monotreme grouping ever recorded. A single specimen has revealed four species, indicating that diversity is still underrepresented. “This discovery adds over 20% to the diversity of monotremes previously known,” McCurry said.
Finding new monotreme fossils will help us learn more about their environment, how they evolved, and where they lived. “Every significant monotreme fossil known today fits into this evolution story, from Teinolophos the tiny shrewlike creature that lived in Antarctica 130 millions years ago, to the present,” McCurry said.
The co-authors of the Museums Victoria Research Institute: Dr. Thomas Rich Senior Curator, Vertebrate Palaeontology and Honorary Associate Prof. Patricia Vickers Rich AO, said that these ancient, curious and unique Australian animals are still able to intrigue the scientific community.
The platypus is an iconic Australian species. “The discovery of several new species within a small area suggests that the family tree for egg-laying monotremes may be more complex than what the platypus or echidna suggest,” said Dr. Rich.
As the fieldwork in Australia’s Mesozoic continues, we continue our understanding of the changes that life has undergone over time. “This is what I find so exciting about science,” said Professor Vickers Rich AO.
Elizabeth Smith, her daughter Clytie and the Australian Opal Centre at Lightning Ridge have spent years searching and working in the opal field.
“Opal fossils may be rare, but monotreme fossils opalized are even rarer, since there is only one monotreme fragment for every million other pieces. Smith said that they don’t yet know where or when the fossils will turn up.
These specimens are a real revelation. They show the world that long before Australia became the land of pouched mammals, marsupials, this was a land of furry egg-layers–monotremes. Smith stated that it appears there were more monotremes in Lightning Ridge 100 million years ago than anywhere else.
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A diverse assemblage of Monotremes (Monotremata), from the Cenomanian Lightning Ridge Fauna, New South Wales Australia, Alcheringa: An Australasian Journal of Paleontology, 2024. DOI: 10.1080/03115518.2024.2348753. www.tandfonline.com/doi/full/1 … 3115518.2024.2348753
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