An amazing discovery in Pakistan adds more clarity to the story of whale evolution. Maiacetus inuus recently discovered and published in the open access journal PLoS One, was found as two adult skeletons (male and female) and one near full term, precocious, fetus within the female skeleton. This is an important discovery since it gives developmental information definitive gender identification of the adult skeletons and a strong suggestion of the delivery method. The fossil fetus was found in a position that strongly suggests that Maiacetus gave birth on land after hauling out of the water. All large land mammals deliver head first, but all marine mammals deliver tail first to very precocious babies. Maiacetus is about 48 million years old and is clearly a transition between the very early amphibious whale, Ambulocetus, and the fully aquatic whales of the Basilosaurus family.
Skull of the adult female and the fetus (colored baby blue)
Even though this ancestral whale has many adaptations, such seal-like bodies and a very powerful swimming tail, maybe even with flukes, and is well on the way to becoming a modern whale, they were still heavy boned and thus not for the open ocean. With the head first birthing position they would have returned to the shore to rest, mate, and give birth. But, like the modern sea lions and their relatives, the maiacetus body was no longer well adapted to life on land. As Ed put it, rather depressingly considering my talents and the economy, maiacetus innus was a jack-of-all-trades and master of none, fully adapted to neither environment.
Artist’s conception of a male Maiacetus innus as it would have appeared in life, with skeleton reconstruction overlaid.
Credit: John Klausmeyer and Bonnie Miljour University of Michigan Museums of Natural History
Read more about this awesome find at: Not Exactly Rocket Science, The Loom, Laelaps and A Blog Around The Clock. This is such a wonderful discovery that each of the aforementioned blogs highlights a slightly different aspect of the discovery.
Here is a National Geographic Channel short video about the Rodhocetus balochistanensis, another protocetecean possibly a contemporary of maiacetus, discovered by the same team.
Of course along with ancient whales I have the opportunity to present another of my father’s images from Antarctica:
A pair of humpback whales feeding on krill in the Antarctic. I love the throat pleats visible in the whale that is feeding on it’s side.
Come a long way from maiacetus innus haven’t they? Amazing animals, even more so when you consider their evolutionary journey.
The humpback feeding picture above was taken where the northern most of the camera icons in this new Google Earth 5.0 (complete with ocean data!) screen shot. The other two camera icons are from the pictures in the previous post.
