University of Calgary

From Feet to Flippers

Searching for Ancient Roots in Marine Reptiles’ Family Tree

PhD student Robin Cuthbertson picks up the torch of another U of C pioneer, alumna Betsy Nicholls, who changed the face of prehistory by unearthing the largest marine reptile ever found.

By Alana Mikkelsen

The Unprepared Collections area, a large, warehouse-like space at the rear of the Royal Tyrrell Museum near Drumheller, Alberta contains the skeleton of an ancient and enormous creature, the largest marine reptile ever found.

Unearthed over three summers between 1999 and 2001 by U of C alumna and renowned paleontologist Elizabeth (Betsy) Nicholls, MSc’72, PhD’89, the 220-million-year-old fossil measures 23 metres long and bears a one-and-a-half-tonne skull. Looking much like a dolphin with an elongated snout, the gigantic reptile, known as an ichthyosaur, transformed scientists’ understanding of life in the prehistoric ocean and launched new questions that researchers are pursuing today.

Robin Cuthbertson, a U of C Faculty of Science PhD student, has embarked on a study to flesh out where ichthyosaurs came from and how they evolved.

“I always thought that studying marine reptiles would be my foot in the door for studying dinosaurs,” says the 29-year-old Winnipeg native, who first encountered Nicholls’ work as an undergraduate student at the University of Manitoba.

Nicholls was legendary for, among other things, conducting an extensive study of marine vertebrate fossils unearthed in Manitoba during the 1970s and 1980s. Her specialty was marine reptiles and Manitoba is rich in material because it once lay underneath a giant inland sea. During the Mesozoic Era—the “Age of Reptiles” between 251 million and 65 million years ago—aquatic reptiles were some of the top predators in the world.

While pursuing his master’s at Carleton University in Ottawa, Cuthbertson studied duckbilled dinosaurs but found he couldn’t turn his back on a group of animals that seemed just as important to understanding how life evolved in the oceans as dinosaurs are to understanding life on land.

“Compared to dinosaurs, there has been much less attention paid to marine reptiles, so it’s exciting to be studying this area of paleontology,” Cuthbertson says.

“The goal of paleontology in a broad sense is to understand the history of life, the main events and the characters involved,” says Donald Brinkman, senior curator at the Royal Tyrrell. An adjunct professor at the University of Calgary since 1992, Brinkman was with Nicholls when they discovered the giant ichthyosaur near the Pink Mountain region of northern British Columbia.

The giant ichthyosaur had no teeth which was significant because it meant that unlike all other known marine reptiles—an entirely carnivorous group—this creature was a filter-feeder. With no gills, the animal probably lived a similar lifestyle to today’s beaked whales and certain sharks, sucking water into its mouth like a giant vacuum and filtering out tiny plankton and small invertebrates. It’s the first record of large vertebrate filter feeders in the fossil record. To support the animal’s immense size meant that the range of life in the prehistoric sea must have been much more diverse and massive than scientists had previously understood.

“It changed our understanding of the biology at that time,” Brinkman says.

Cuthbertson thinks ichthyosaurs are especially interesting because they lasted nearly as long as the dinosaurs, and because they exhibited such tremendous variation in form. By the middle of their evolution, in the period of Nicholls’ giant ichthyosaur, they were extremely successful open-water swimmers, having developed a sleek torpedo-shaped body, with well-developed flippers—an efficient body plan suited to their lifestyle.

But it wasn’t always so. The oldest ichthyosaurs, near the beginning of the Mesozoic Era, were a lot smaller and looked more like lizards, with the kind of fingers one might find on a land-dwelling reptile like an iguana.

That fact begs the question: How did ichthyosaurs evolve from feet to flippers?

To find the answer, Cuthbertson plans to look this summer for fossils from the earliest period of the Mesozoic Era—the Triassic— as much as 251 million years ago, when early marine reptiles were first developing and moving into the sea from the land. His goal is to investigate the ancestors of ichthyosaurs and the relationships among different marine reptile groups.

“Investigating the origin of ichthyosaurs will increase our understanding of the early Triassic,” he says. “There are a lot of gaps in our knowledge because there are few places in the world where we find an abundance of fossils this old.”

For the paleontologist looking for early Triassic remains, northern B.C.’s Tumbler Ridge area is paydirt. A remote location with rough terrain, it once lay at the western edge of a shallow inland sea. In the warm, relatively still water with few bacteria, deceased marine animals would have fallen to the silty bottom and been buried fairly quickly with little disturbance. Those conditions, combined with the erosion that has exposed the ancient sea bed since the mountains arose, increases the chances of finding a large accumulation of well-preserved fossils. And that’s what researchers have found so far.

“It’s one of the biggest sites in the world for early stages of evolution of this particular group,” says Dr. Anthony Russell, a U of C zoologist who supervised Nicholls’ PhD survey of the Manitoba reptiles and who is co-supervising Cuthbertson’s work.

Cuthbertson hopes to learn which of several primitive reptile groups might be the definitive ancestor of ichthyosaurs. The subject has long been debated because the earliest ichthyosaur fossils were already somewhat adapted to water.

The question of ancient family ties is not a trivial one, notes Russell. “If our closest relatives were cows, we would have a totally different understanding of who we are,” he says.

Birds, for example, are now commonly regarded as descendants of dinosaurs. But for a long time, they were placed much closer to other reptiles, including a group known as the crocodillians, Russell explains. By teasing out ancestral relationships, scientists can begin to understand, for example, how birds became birds and how powered flight originated.

And for ichthyosaurs, it might be possible that they shared a common ancestor with the dinosaurs themselves.

“We think the ancestor of the ichthyosaurs is a primitive diapsid, one type of early reptile,” says Brinkman. Scientists already agree that dinosaurs evolved from primitive diapsids. The question is, did ichthyosaurs evolve from the same sub-group? To probe these mysteries, Cuthbertson plans to helicopter in to Tumbler Ridge and hike the irregular terrain looking for telltale surface outcroppings, which he can then return to excavate.

To be sure, Cuthbertson is playing the odds. Complete skeletons of early marine reptiles are rare, and none has ever been found of the earliest ichthyosaurs or their diapsid ancestors. But a fall 2006 expedition to the site by Brinkman and Jason Anderson, an assistant professor of anatomy in the Faculty of Veterinary Medicine and Cuthbertson’s other supervisor, revealed numerous exposed skeletons on the surface of the rock.

“We’d be really lucky to find a skull with an intact body attached,” says Cuthbertson. Because, as Betsy Nicholls knew, great insights can be gleaned from a skull.

Elizabeth (Betsy) Nicholls unearthed the world’s largest known
ichthyosaur in northeastern B.C. between 1999 and 2001.
/ Photo Rolex Awards /T omas Bertelsen

Legacy of a fossil hunter

Elizabeth (Betsy) Nicholls, MSc’72, PhD’89, said that finding a fossil is like discovering a lost page in the planet’s history book. Perhaps that explains why she was always so ready to trek across remote terrain, often with her family in tow, in search of new fossils that would push her beloved science forward.

One of the most accomplished and celebrated vertebrate paleontologists in Canada, Nicholls conducted a broad range of studies that changed the face of prehistory in many ways. She discovered numerous new species, opened up new avenues for studying evolution and transformed scientists’ understanding of what life was like in the ancient ocean. She died in 2004 of breast cancer, but her legacy continues in the form of an impressive collection of fossils that researchers from across the globe study today.

Known internationally, Nicholls was the first Curator of Marine Reptiles at Alberta’s pre-eminent Royal Tyrrell Museum and co-edited a textbook on marine reptiles that became the bible for scientists in the field. Aside from discovering the world’s largest marine reptile, she collected and studied North America’s oldest known plesiosaur (a seal-like giant discovered north of the Crowsnest Pass) and unearthed one of the largest known mosoasaurs, a crocodile-like creature that has been called the Tyrannosaurus rex of the sea.

For 14 years, Nicholls worked at the Royal Tyrrell Museum, making the 280-kilometre round trip daily from Calgary to the wind-eroded swells of Drumheller’s badlands. Passionate, energetic and meticulous, she traveled often to many isolated places in western Canada, unearthing some of the most noted marine reptiles of prehistory and, in the  process, making famous the region’s fossil-rich beds—including a site near Wapiti Lake in northern British Columbia that she established as one of the world’s most important sites for Triassic marine reptile fossils. Her ashes are scattered there.

A newly described species of mosasaur will be named for her in an upcoming issue of the Canadian Journal of Earth Science, continuing a trend of recognition by colleagues and students alike. Given Nicholls’ lasting impact on the field of paleontology, the tribute is likely not the last.