As bones encased in rock rotted away, water-borne silica seeped into the crevices, solidifying into opal and preserving treasured particulars for 100 million years. The ensuing fossils now present proof that there actually could have been an Age of Monotremes, earlier than different mammals got here to dominate.
“It’s like discovering a whole new civilization,” says Australian Museum paleontologist Tim Flannery.
“Today, Australia is known as a land of marsupials, but discovering these new fossils is the first indication that Australia was previously home to a diversity of monotremes.”
Solely 5 of those uncommon mammals nonetheless cling to existence: one platypus and 4 echidna species, shared between Australia and Papua New Guinea. However as a result of their reptilian-like egg-laying characteristic, it has lengthy been thought these animals developed earlier than placental mammals like us and marsupials.
“It may be guessed that, wherever they originated, monotremes radiated in Australia before marsupials did, and that the old Australian monotreme fauna may have been at least as diverse as the later marsupial fauna… ” naturalist Philip Jackson Darlington speculated again in 1957.
Whereas this idea is extensively accepted, fossil proof has remained scarce.
Now, three newly found monotremes convey the full of fossil species identified on this one place and time interval to 6, proving there actually was some range amongst these furry egg-layers. The brand new finds vary from the scale of a small possum to that of a cat, Flannery informed James Woodford at New Scientist.
Australia’s Lightning Ridge in northeastern New South Wales, the place the fossils had been discovered, now has probably the most various vary of monotreme fossils on report, all from the Cenomanian interval between roughly 100 and 95 million years in the past.
“Four species are known from a single specimen, suggesting that diversity remains underrepresented. This discovery adds more than 20 percent to the previously known diversity of monotremes,” says Australian Museum paleontologist Matthew McCurry.
Among the many new fossils is the toothy ‘echidnapus’ (Opalios splendens), who, as its nickname suggests, shares traits of each echidnas and platypuses. It has the lengthy slim snout of an echidna but in addition some options of a platypus, like complicated electroreception.
“The story of how our egg-laying mammals evolved is ‘toothy to toothless’,” describes Australian Museum mammologist Kris Helgen.
“The oldest monotreme, Teinolophos trusleri, which dates again to Victoria 130 million years in the past, had 5 molars in every jaw. What we see at Lightning Ridge is that by 100 million years in the past, a few of the monotremes nonetheless have 5 molars however a few of them are down to 3.”
Fashionable echidnas don’t have any enamel and platypuses lose theirs earlier than they absolutely mature.
Flannery and colleagues additionally describe the tiniest identified monotreme, Parvopalus clytiei, and Dharragarra aurora, which has an identical jaw to fashionable platypuses, of their new paper. These be part of the three beforehand found historical Lightning Ridge monotremes: Kollikodon ritchiei, Steropodon galmani, and Stirtodon elizabethae, the biggest identified monotreme.
Up to now researchers have discovered no different indicators of mammals from this era, suggesting that monotremes actually could have been alone amongst the dinosaurs of that period. Nonetheless, a extra in depth fossil assemblage that features different websites will likely be wanted to substantiate this idea.
This analysis was printed in Alcheringa: An Australasian Journal of Palaeontology.
