Ancient Whale Gave Birth on Land
Feb. 4, 2009 -- A rare fossil of an ancient whale with a fetus still inside reveals that its species -- an ancestor to modern whales -- gave birth on land 47.5 million years ago, according to a paper published in the online journal PLoS.
The discovery, along with prior fossil finds, suggests the first whale ancestors were full-time land dwellers that might have been related to the early relatives of hoofed animals, such as sheep and cattle.
Maiacetus inuus, meaning "mother whale," represents an intermediate evolutionary stage. It lived at the land-sea interface and often moved back and forth between the two environments in what is Pakistan today.
It looked like an improbable cross between a cow, whale, shark, alligator and sea lion.
"Maiacetus was a long-snouted, short-haired mammal with short limbs, webbed hands and feet retaining small hooves on some fingers and toes, and it had a thick, long tail," lead author Philip Gingerich told Discovery News.
Gingerich, a University of Michigan paleontologist, added that the whale "was a foot-powered swimmer and probably lived like a sea lion, spending part of the day or night resting on land and part of the day or night searching for food in the sea."
The fetus was positioned for a "head-first" delivery like land animals, but unlike modern whales. This provides the biggest clue that the species gave birth on land.
The fetus also had a well-developed set of teeth, suggesting it "would be able to get up and move shortly after birth, probably having to keep up with its mother, learning to feed and escape predators," Gingerich said, adding that it would've had to defend itself against very large sharks.
He and his colleagues were stunned to find such a rare fossil, the first ever of its kind.
"To be honest, I never expected to be able to find a whale about to give birth," he said. They also found an 8.5-foot male of the same species at the site.
Since the male whale was only moderately larger than the female, the researchers suspect males of this species didn't control territories or command harems.
Ewan Fordyce, head of the Department of Geology at the University of Osago in New Zealand, told Discovery News, "The convincing presence of a fetus makes this a most important find."
"Fetuses are rarely reported for fossil land mammals," he explained, "and as far as I know, this is the first such case for a whale or, for that matter, any fossil marine mammal."
Fordyce added that the findings are timely, given the forthcoming 200th anniversary of British naturalist Charles Darwin's birth, which occurred on February 12, 1809.
"Darwin would have reveled in such evidence for a major shift in the fossil record," Fordyce explained, referring to the whale's dramatic transition from land to sea.