FEATURE

A modern sea turtle distantly related to the fossil find on the Puntledge River.

By Derek Larson

Collections Manager & Researcher, Palaeontology

Discovering a Fossil Turtle from BC’s Ancient Seas

FOSSIL IN A HALFSHELL

Excavation of the fossil turtle along the Puntledge River with Royal BC Museum palaeontologist Derek Larson and discoverer Russell Ball.

PUNTLEDGE RIVER

COURTENAY

NANAIMO

VICTORIA

Russell Ball, who discovered the fossil turtle, before the fossil was transported to the Royal BC Museum. The Puntledge River near Courtenay, BC, where the fossil was discovered earlier this year.

Eighty-five million years ago, while dinosaurs walked on land, marine reptiles topped the ecosystem beneath the waves: long-necked plesiosaurs, giant marine lizards like mosasaurs, and sea turtles the size of modern leatherback sea turtles. Just north of the tropics, on a shallow marine shelf on the east coast of Wrangellia, a partial skeleton of just such a turtle sank to the silty bottom of the sea floor. Scavenged by both fish and invertebrates, the bones of this turtle came to be buried beneath the shallow sea waters, where they would be fossilized for millions of years before being uncovered by a chance encounter.

This turtle, like its larger three- and four-metre-long relatives, Archelon and Protostega, had a flattened, not-completely-bony shell, flippers instead of feet, and a sharp beak for catching squid and their shelled relatives, the ammonites.

The find was a surprising one. It was a warm day at the end of January 2021. Russell Ball was used to finding ammonites, fossil clams and fossil crustaceans along the Puntledge River just outside Courtenay, BC, but he was not expecting to find bone—especially what appeared to be flat, plate-like bone larger than the palm of his hand—sticking out of the hard, grey rocks along the banks of the river. Russ knew that the find was significant, and that it should go to a museum for study, but he needed help. He approached Dan Bowen, the president of the Vancouver Island Paleontological Society, to come and check out his find. (continues next page)

(right) Surface detail of the brown fossil turtle in the grey rock it was buried in. This is part of the underside of the shell, or plastron.

(far right) The roughly one-metre-long block with the turtle skeleton inside before it was encased in burlap and plaster to protect it for transport.

Dan returned to the site with Russ and confirmed his suspicions: it was a fossil turtle. But by the time they returned the next week, the fossil was already submerged by the rising river water. To protect it for the short term, they built a cairn over it. But the fossil needed to be collected to avoid any further damage from water flow or from accidentally being stepped on.

The two knew that they had to work within BC’s fossil laws to make sure it was safely collected. Since 2005, BC’s Fossil Management Framework has required excavation permits on any fossil that’s embedded in rock on Crown land. And these permits are only issued to professional palaeontologists.

They contacted Elisabeth Deom at BC’s Heritage Branch and two palaeontologists, Dr. Victoria Arbour and myself, at the Royal BC Museum. We also reached out to the K’ómoks First Nation, whose traditional territory includes the area where the fossil was found. Luckily, the find matched up well with my research goals of investigating rare fossil turtle remains in BC, and I was granted a permit to collect.

Meanwhile, a BC Hydro dam on the Puntledge River had opened up to allow more water through, and within a few hours the river level had risen over 30 centimetres. Downstream, the water had completely submerged all of the low-lying rock on the river bank. Luckily the turtle fossil, under its cairn of stones, was held in place as the waters rose.

Working along a river has advantages and disadvantages. The main advantage is that flowing water, through the power of erosion, does most of the work excavating fossils buried in the rock. No palaeontologist goes out and just digs a hole without first having some indication that there will be a fossil there—at least part of the fossil has to be exposed at the surface. The disadvantage of working near rivers is that flowing water can also erode the fossil itself, and fossils are virtually impossible to collect under water without severe risk of their being destroyed. Furthermore, river flow is often unpredictable and difficult to control. In this case, we were fortunate that we did have some control. Thankfully, BC Hydro was able to manage the water levels for a week in April, keeping it low enough to extract the fossil.

So, that’s how I found myself in a parking lot in Courtenay, BC, on April 12, 2021, fully masked and ready for fieldwork. I had one week to get the fossil collected and back to the museum.

With Russ and Dan’s help, along with the assistance of a rotating cast of local volunteers, we were able to trace a rough outline of the fossil in the rock. It turned out to be more complete than Russ’s initial find had indicated. We collected a block more than 1 metre long, 60 centimetres wide and only 20 centimetres thick that Russ affectionately named “Mr. Russellufagous” as a nod to the big friendly Muppet on Sesame Street. We got the burlap and plasterencased fossil back to the museum on April 16, just as the spring melt raised the water level, counteracting what our friends at BC Hydro had done to accommodate us in our endeavour.

Back here at the museum, Mr. Russellufagous sits patiently to be slowly extracted from its rocky resting place to share the secrets it has kept for 85 million years.