Read part one of this two-part series.
It’s not easy researching fossils; nor is it quick.
“Hundreds of hours, just with a little brush pushing little bits of bone fragments to the sides looking for bits of teeth.”
That’s Flinders University doctoral candidate Arthur Crichton, describing the painstaking daily grind of palaeontological research, something he agrees is akin to a “very slow-burn detective job.”
Crichton is lead author on a recent research paper documenting Mukupirna fortidentata, the 25 million-year-old cousin of an Australian wombat ‘crossed with’ a marsupial lion, unearthed at the Pwerte Marnte Marnte site near Rainbow Valley, about 75km south of Alice Springs. Crichton had worked closely with palaeontologists from the Museum of Central Australia, Adam Yates and Sam Arman, with whom I had recently travelled to the PMM site.
I wanted to know more of Mukupirna, but also any news on Dr Sam Arman’s discovery at the PMM site (See part one of this article) when he prised loose a slab of rock, and on its underside found a trochlea: the knuckle joint at the end of a foot bone of an emu-sized bird. What sort of bird was it exactly? How big might it have been?
Patience not being my strong suit, I managed to contain my curiosity—at least at first—in deference to Crichton’s never-before discovered species of M. fortidentata, which had attracted excitement and international media attention when the news was published.
“Hundreds of hours, just with a little brush pushing little bits of bone fragments to the sides looking for bits of teeth.”
Arthur Crichton
And telling its story seemed to provide Crichton with a well-deserved break from the long hours of research, which for him is motivated “by the potential for discovery at any moment.”
“It’s always exciting when there is a new fossil deposit found in Australia,” Crichton says, “particularly one that bears vertebrate remains, because the Australian fossil record is really quite incomplete.
“PMM is significant because it is thought to preserve the oldest iconic animal groups from Australia that can be related to modern forms. From a morphological standpoint, [M. fortidentata] has some general similarity to both wombats and marsupial lions, particularly with respect to its front tooth morphology.
“The teeth are very large and upward pointing and that’s one of the main points of similarity to marsupial lions and the other aspects of its morphology, [however] from an evolutionary standpoint, it’s thought to be more closely allied to the wombats.”
Still, popular appeal for the animal discovered does not lessen the amount of careful work required for the palaeontologist to document and substantiate its identity and ancestry.
“It’s always exciting when there is a new fossil deposit found in Australia, particularly one that bears vertebrate remains, because the Australian fossil record is really quite incomplete.”
Arthur Crichton
“Most of the time that goes into recovering fossils comes after the field work,” Crichton says. “You head to the site for a couple days and quarry a few hundred kilos or a tonne of rock and then process that back at the lab with a low concentration of acid as well as mechanical methods.”
Crichton, therefore, has no field outings planned any time soon.
“I just don’t have time to process more in the time I have [left] with my PhD; the amount of time you spend processing the rock … it’s an order of magnitude greater than [the] field work.”
Crichton twice visited the PMM site but has spent much of the past year processing and writing up results, and with still more to be done.
“There’s still a couple of hundred kilos at Flinders waiting to be processed.”
When I visited the PMM site in May, MCA’s Dr Adam Yates had described the laboratory process with the same due reverence. Part of the challenge, he says, is caused by the in situ conditions of the bones themselves; at the dig, he noted there were “bones poking out of the sediment all over the place, and they’re not in very good shape, very badly cracked and crushed.”
“The reason,” says Yates, “is that the sediment has been subject to soil forming processes since it was deposited.”
And soil formation is bad for bones, apparently, so as well as being crushed and mangled they are also quite corroded, very soft and don’t hold up well to handling. The consequence is a long, slow process at the laboratory, as Yates goes to some lengths to explain.
“You take a sample, a lump of rock that you think has some bones in it that are worth getting out, and you bathe it in an extremely weak solution of acid for a few hours; overnight at the longest.
“[The acid] will eat away at the lime, the calcium carbonate that is cementing all the sand grains and pebbles together, but hopefully not attack the bone at the same rate. It does attack the bone, but it doesn’t attack it as fast, so if you only leave it in for a short while, hardly any of the bone gets damaged—hopefully—but the rock that’s encasing it will start to lose some of the cement that’s holding the grains together.
“Then you rinse all the acid out of it [and] leave it to soak in some fresh water for a long time to get the acid out.”
The sample must then be dried, and only then will a palaeontologist risk using a mechanical device to probe further.
“We actually prefer a tool called a micro-jack,” says Yates, “a little vibrational hand-held tool that can just chip away at the softened rock surrounding the bones. You harden any exposed bones with a plastic solution that is dissolved in acetone that then impregnates the bone, gets into all the cracks, and helps bind it and consolidate it, gives it strength and helps it resist the acid when it goes back into the next acid bath.
“Once you’ve done that, and you’ve hardened it all up and you’ve etched away a little, probably exposed two millimetres or so of bone, you put the rock back into another bath of weak acid for another few hours or overnight. Then you repeat the process, and slowly—and this takes months, months of work—you slowly work back the rock and expose the bone and gently tease it out, hopefully in one piece. Then we can study it and find out what exactly it is.”
At least now I understood why the pace of fossil research is sometimes compared with that of the geological processes that form them
Given the mountain of work Crichton faced, I had become somewhat reluctant to ask about Sam’s slab. But the truth was, I couldn’t wait.
Sadly, it turns out word of the slab had not reached Adelaide; I guess there is as much work running a museum as a research lab. Word on the “emu-sized bird” would have to wait for the wheels of palaeontology to turn just a little farther.
At least now I understood why the pace of fossil research is sometimes compared with that of the geological processes that form them; in other words, I wouldn’t hold my breath …
