Most people think of fossils as neatly mounted skeletons displayed in cool, clean museums with nicely printed labels at their feet.
Unfortunately, says Tim Tokaryk, assistant curator of paleontology at the Saskatchewan Museum of Natural History, they don’t occur that way in nature–though he wishes they did!
Tokaryk became interested in paleontology as a volunteer at the Provincial Museum of Alberta. His first day, he says, they plopped the ilium (a pubic bone) of a duck-billed dinosaur on his desk and told him to go to work–and he was hooked.
He’s been at the Museum of Natural History for 10 years, and has gone on lots of fossil-hunting expeditions, such as the one in 1991 that uncovered “Big Bert,” a 92-million-year-old crocodile whose fossil he’s been preparing at the Science Centre, in among the animated dinosaurs on display this summer.
Finding fossils, Tokaryk says, takes both luck and skill. First, he looks for exposed bedrock (not part of the Pre-Cambrian Shield, since there were no vertebrate animals when it formed) in places where rivers or glaciers have carved up the land, such as Big Valley. He might look for bedrock of a certain age (by checking geological surveys) if he needs a particular kind of specimen.
Experience pays off when he starts searching the rock for fossils, Tokaryk says. He’s built up an image-bank in his head of what certain bones look like, which makes it easier for him to recognize one if he sees it poking out of the rock. As for luck, well, “Science stumbles bravely on,” Tokaryk says: the sun might be at just the right angle, or he might come across a hillside just when erosion has exposed a skeleton.
Typically one piece of a fossil is found on a hillside and other pieces at the hill’s base, because the same erosion that exposes fossils also destroys them. The first task is to dig carefully around the bone to see if there’s more inside the hill. If there is, then the next step, Tokaryk says casually, is “to remove the hill.”
That could just be a matter of stripping away a metre of soil–or, as in the case of Big Bert, removing five tonnes of shale. Either way, it means a lot of back-breaking work with pick and shovel, or even jackhammers and dynamite.
Once the overlaying material is stripped down to within 30 centimetres or so of the fossil, hand tools are used to follow the bone into the rock, to see how much is there. Next to the discovery itself, Tokaryk says, “that’s the fun part.”
When the fossil’s extent is known, a trench is cut around it, and then it’s cut into smaller blocks. Tokaryk tries to avoid cutting through bones, but sometimes has to, because usually he’ll be carting the fossils out on foot–though he did use a helicopter once for a particularly heavy piece.
The blocks are coated with about seven layers of burlap and plaster of Paris, with some two-by-fours between the third and fourth layers for stability. The top is covered first, then the block is flipped over and the bottom is covered.
Everything is also photographed and thoroughly mapped, and the rock is sectioned to help date the fossil and determine its ancient environment.
The plaster-covered blocks (big ones can weigh a tonne) are then taken to the museum, where Tokaryk uses very fine tools to free it from the rock, from the bottom up (because the top, having been exposed, is already partially prepared).
That preparation consists of coating the bone, as it is freed, with a shellac-like glue (thinned so it will penetrate the bone better). The glue helps minimize fractures, particularly in small bones.
Once free of the rock, the fossil is carefully catalogued and then studied. Paleontologists want to know what it is, what its environment was, and most of all, “What does it mean?” in terms of the history of that species and life in general.
Some fossils, after the initial study, are simply stored; others, destined for display, are replicated: latex rubber is painted over the bone to form a mold, and fibreglass or foam casts are made. It’s these replicas that you see mounted and displayed in museums.
The whole process, from discovery to display, takes years. Tokaryk says the fossil of a typical duck-billed dinosaur takes three weeks to collect, a year and a half to prepare, two months to replicate and a month to mount, with up to a year of research added in. That’s why he says the first thing he gets after the thrill of discovery wears off is a headache.
Yet Tokaryk says the rewards are worth the backbreaking work in the field and the painstaking work in the lab. One of our great attributes as a species, he says, is that we’re always asking “why?” That basic curiosity is the foundation of all the great discoveries of science, and it’s why he’s a paleontologist.
“I learn,” he says. “If it’s the ilium of a frog that lived 65 million years ago or the skeleton of a crocodile, I’m always learning something new. That’s the biggest kick I get.”