Ed Yong, over at his excellent blog Not Exactly Rocket Science has posted about the fetus found within the fossilised remains of Maiacetus inuus (Fossil foetus shows that early whales gave birth on land). It’s another case of the so-called “missing links”, really. In this case an intermediate between terrestrial vertebrates and fully aquatic cetaceans. What’s particularly neat here is the presence of a fossilised foetus within the larger animal’s remains. This clearly indicates that Maiacetus was amphibious, as the foetus is oriented so as the born head-first. Head-first birth is never found in modern cetaceans, as the newborn animal would likely drown.
Other reports include the following blogs: