Pyenson is curator of fossil marine mammals at NMNH. He is interested in how different lineages of four-limbed animals have repeatedly invaded oceans from land ancestry over the past 250 million years – an evolutionary cross-section of vertebrate life that includes sea turtles, seabirds, and especially marine mammals, such as whales. His scientific expeditions have taken him to every continent, with a strong focus on paleontological exploration, anatomical discovery, international mentorship, and 3D digitization for museum collections. Along with his collaborators, he has named over a half-dozen new fossil species, discovered the richest fossil whale graveyard on the planet, and described an entirely new sensory organ in living whales. Currently, he is writing a popular book about the origin and future of whales, to be published in 2018 by Viking Books.