Early whales gave birth on land, fossils reveal
SMU paleontologist Louis Jacobs talks about the recent discovery of fossils showing that early whales gave birth on land.
By Tasha Eichenseher
National Geographic NewsÂ
Forty-seven million years ago primitive whales gave birth on land, according to a study published this week that analyzes the fossil of a pregnant whale found in the Pakistani desert.
It is the first fetal fossil from the group of ancient amphibious whales called Archaeoceti, as well as the first from an extinct species called Maiacetus inuus.
When the fossil was discovered, nine years ago, University of Michigan paleontologist Philip Gingerich was thrown off by the jumble of adult and fetal-size bones.
"The first thing we found [were] small teeth, then ribs going the wrong way," Gingerich said. Later, "it was just astonishing to realize why the specimen in the field was so confusing."
The head-first position of the fetus was especially telling. Land mammals are generally born head first, and marine mammals are born tail first. . .
The most famous other seafaring animals to be found fossilized with a complete fetus were ichthyosaurs, a reptile group that lived roughly 245 to 100 million years ago.
"Not since have we seen fossils of marine-dwelling vertebrates that tell us so much about the biology of evolving an ocean dwelling way of life from a terrestrial ancestor," said Louis Jacobs, a vertebrate paleontologist at Southern Methodist University in Texas.
"It is a missing link of the most informative sort," Jacobs added. "Charles Darwin would delight."
February marks the 200th anniversary of Darwin's birth and the150th anniversary of publication of the Origin of Species.
(Read more about Darwin's evolutionary theories in National Geographic magazine's "Darwin's First Clues" [February 2009].)