Thomas Cullen and Dr. Natalia Rybczynski examine fossils at the Canadian Museum of Nature’s collection facility in Gatineau.
Scientists now know more about the early evolutionary history of seals, sea lions and walruses thanks to a researcher’s discovery at the Canadian Museum of Nature.
A study by Carleton University earth science student Thomas Cullen, published in the International Journal of Organic Evolution, provides insight into the early evolution of the family of marine mammals known as pinnipeds.
Examining a 20-million-year-old fossil of a sea lion ancestor, Cullen found what was previously thought to be an infant animal was actually a full-grown female.
The research sheds light on when sexual dimorphism – in which males are much larger than females – emerged in the species. Cullen’s discovery traces it back 20 to 27 million years ago.
“I’m hopeful my discovery is helpful to those going forward trying to answer more of these evolutionary questions,” says Cullen.
Cullen was able to examine the fossil at the McLeod Street museum after it was loaned from the Smithsonian Institution in Washington, D.C. According to Cullen, it had not been examined since its discovery in the 1980s.
After determining the fossil was female, Cullen matched it with with empirical data on the skull structure of modern pinnipeds. Using this research method, Cullen and fellow Carleton student Danielle Fraser were able to place the fossil within the same category of sexual dimorphism that occurs in modern day sea lions.
“When we included the fossil, suddenly the relationship became a lot clearer,” says Fraser.
The fossil was sent to the Canadian Museum of Nature to help with the research of one of its paleontologists, Dr. Natalia Rybczynski, whose focus on pinnipeds began after her discovery of another pinniped fossil in the Canadian Arctic in 2009.
“This finding is a fine example showing the importance of the fossil record for understanding the evolution of mating system and biodiversity in mammals,” says Rybczynski.