Tale of 2 Tails: Why Do Sharks and Whales Swim So Differently?
By Laura Geggel, Senior Writer |
May 20, 2017 11:45am ET
The graceful whale swims by undulating its wide tail up and down. And so does the shark, right?
Like other fish, sharks swim by moving their tails side to side. So, why do these two marine creatures — the shark and the whale — swim in such different ways? [What's the World's Largest Whale?]
Whales move their tails up and down because they evolved from mammals about 50 million years ago, said Kenneth Lacovara, a professor of paleontology and geology and the dean of the School of Earth & Environment at Rowan University in Glassboro, New Jersey.
"When quadrupedal [four-legged] mammals run, their spine flexes up and down," Lacovara told Live Science. Whales retained this anatomy, which allows them to gallop underwater, so to speak, Lacovara said.
The oldest known relation in the modern whale lineage is Pakicetus attocki, a four-legged, wolf-size mammal that likely had webbed feet. P. attocki lived on the edges of a shallow ocean and chowed down on fish about 50 million years ago, Live Science previously reported.