If not for the tenacity of paleontologist Elizabeth "Betsy" Nicholls, the remains of the biggest prehistoric marine reptile ever found might still be embedded in the remote wilderness of British Columbia.

After its discovery by an archaeologist in the limestone banks of Sikanni Chief River, scientists initially decided that the nearly 75-foot-long ichthyosaur fossil was too big, too fragile, and too isolated to excavate. Moreover, the site, prime bear territory and mosquito-infested, was accessible for only a few summer weeks a year.

But Nicholls, curator of marine reptiles at Canada’s Royal Tyrrell Museum, was undeterred—particularly after she realized that the 18-foot-skull she had thought belonged a blue whale was actually a new species of ichthyosaur. She named the filter-feeding ocean dweller—which looks part dolphin, shark, and whale—Shonisaurus sikanniensis.

View Images This fossilized ichthyosaur is similar in shape and age—but not size—to the giant unearthed by Nicholls. Photograph by Tomas Bertelsen, Rolex Awards

Before the Rolex Laureate’s death from breast cancer in October 2004, Nicholls began a multiyear fundraising and excavation effort to exhume the skeleton. Paleontologists regard her effort as one of the most ambitious fossil excavations ever undertaken.

“Nobody else would have tried to excavate something this big,’’ says Don Brinkman, director of preservation and research at the Royal Tyrrell Museum, where the fossil is on display. “Personally, I didn’t think we could do anything but take a sample and document its appearance—but that’s where Betsy persevered.’’

The drive to the site took 12 hours from her base near Calgary, followed by a two-mile hike. Work crews required jackhammers and power saws to slice the skeleton, encased in rock, from the riverbank. Helicopters ferried equipment and work crews over the four years it took to complete excavation.

“It’s really been worth all the effort—it rewrites the history of what we know about the ichthyosaur,’’ Nicholls said before her death.

View Images Nicholls and a researcher work on removing an ichthyosaur's skull from its limestone encasement. Photograph by Tomas Bertelsen, Rolex Awards

Nicholls became fascinated with paleontology as a grade-schooler but was unsure if the male-dominated field would welcome women. As a 12-year-old, she sought advice in a letter to paleontologist Roy Chapman Andrews, then director of the American Museum of Natural History. Nicholls kept Andrews' encouraging response as a treasured memento.

Still, Nicholls didn’t complete her doctorate work until after raising her two daughters into their early teens.

“Betsy didn’t like to be identified as a role model, but she was to a lot of people,’’ Brinkman says.

Nicholls’s last academic paper, co-authored with paleontologist Makoto Manabe, appeared in the Journal of Vertebrate Paleontology two months after her death. It established the scientific community’s acceptance of Shonisaurus sikanniensis as a new ichthyosaur species, opening new areas of evolutionary research.