Sperm Whale

Associated Smithsonian Expert: Nicholas D. Pyenson, Ph.D.

Dr. Nick Pyenson wraps up a long day excavating a fossil dolphin skeleton with colleagues in Panama

Photo by Aaron O'Dea, Smithsonian Tropical Research Institute

Dr. Nick Pyenson is a curator in the Department of Paleobiology at theSmithsonian National Museum of Natural History with special expertise in the evolution of marine mammals. Nick grew up in Quebec and Louisiana, and was lucky enough to have relatives who supported his avid interest in fossils and natural history. In college, he took a variety of field courses in botany, stream ecology, and human paleoecology (the latter which took him to Africa), convincing him that science and the outdoors (and especially with international travel), was a good way to spend time. After earning his doctorate from U.C. Berkeley in 2008, he was as a postdoctoral fellow at the University of British Columbia before joining the Smithsonian in 2010. At the Smithsonian, Nick tends to the world’s largest collection of fossil marine mammals, and he contributes to it with field programs around the world, including most recently on Vancouver Island in Canada, and with South American collaborators in the Atacama Desert of Chile. Nick thinks that marine mammals, such as whales, sea cows and sea lions are ready-made vehicles for enhancing a deeper understanding of fundamentals evolutionary biology and earth sciences. He is especially interested in using digital tools that can expand fieldwork, outreach and natural history collections all at the same time.

Meet our associated expert

This image was obtained from the Smithsonian Institution. The image or its contents may be protected by international copyright laws.

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Fossil skeleton of Eocene cetacean (Basilosaurus) on display at the National Museum of Natural History
Photo by Chip Clark, Smithsonian, National Museum of Natural History

About Cetaceans (Order Cetacea): Paleobiology

The first cetaceans on Earth were not much like the whales, dolphins, and porpoises of today. They appear in the fossil record in the early Eocene (about 55 million years ago). Cetaceans evolved from land animals that made a gradual transition to water. The earliest cetaceans were semi-aquatic, living along the shores of the ancient Tethys Sea. Using all four legs, they probably half-swam, half-crawled through the water like hippos. By the mid-Eocene (about 45 million years ago), cetaceans became more seaworthy, with long noses, blowholes, webbed toes, strong tails, and flexible backbones for swimming. Front legs gradually evolved into flippers, and hind legs got smaller. It wasn’t until the Oligocene (about 35 million years ago) that hind legs disappeared into the body as remnant (vestigial) bones. Cetaceans were fully aquatic by the late Eocene and eventually developed the big brains and thick blubber that we see in today’s whales.

Depiction of cetaceans in the ancient seas
Artwork by Ely Kish. Photo by Chip Clark, National Museum of Natural History

About Cetaceans and Artiodactyls (Superorder Cetartiodactyla): Evolution

It might seem odd to group Cetaceans (whales) with Artiodactyls (hooved animals such as pigs, deer, camels, llamas, and hippos). But that is exactly what the combination of their scientific names into Cetartiodactyla is about. For some time, scientists had proposed that whales descended from land mammals, with the focus on the hooved fossil Mesonychia. In the 1990s, DNA sequences from many different genes revealed a closer relationship between whales and hippos than between hippos and any other hooved mammals. While it is not yet known what common ancestor whales and hippos share, the newly discovered relationship is getting attention. It appears that whales and hippos may have branched off from Artiodactyls as long as 60 million years ago. Scientists have proposed a new group called Whippomorpha (wh[ale] + hippo[potamus]; morphe = form) to include whales and hippopotamus and exclude other hooved animals.