View from the side and below of the skull, rib cage, and forelimbs a maiacetus inuus in the Sant Hall of Oceans in the Smithsonian Museum of Natural History in Washington, D.C. Maiacetus means "mother whale," and Inuus was a Roman god of fertility god. The first skeleton of this ancient whale-like animal was found in Pakistan in 2009, and was a pregnant female with an unborn calf (hence the name).Maiacetus inuus is an "archeocete," which means "ancient whale." It wasn't really a whale, but rather an ancestor of whales which lived both on land and in the ocean (although it lived primarily in the latter). It had bit, sharp, long teeth and ate fish. Maiacetus probably came out of the sea only to rest, mate, and give birth. Its four legs were adapted for foot-powered swimming. The legs could support the maiacetus on land, but they probably couldn't travel very fast or very far inland.This ancient whale-like animal was about 8.5 feet (2.6 m) in length and weighed about 620 to 860 pounds (280 to 390 kg). It lived about 49 to 40 million years ago. The fingers of each foot were elongated, and probably webbed. The hind feet were much larger than the forefeet, which shows how already the limbs were beginning to atrophy and turn into a fluke. The snout was highly elongated as well, good for snapping at fish.The position of the fetus (head-first) suggests that these whales gave birth on land. (Land mammals almost all give birth head-first. Whales give birth tail-first.) The fetus has fully developed teeth, which indicates it was able to fend for itself immediately after birth.A male maiacetus inuus has also been unearthed, and it is about 20 percent larger than the female. This is not much at all, which indicates that males didn't control territories or command harems.
Dorudon atrox ("Spear-Tooth") skeleton in the Sant Hall of Oceans in the Smithsonian Museum of Natural History in Washington, D.C. (The lower jawbone of a modern right whale can be seen just behind it.)Dorudon was an ancestor of the modern whale that lived 41 to 33 million years ago. Its much larger cousin, the Basilosaurus, lived at about the same time. Both were the first animals to qualify as whales, as they both lived completely in the ocean. Dorudons grew to be about 16 feet (5 m) long, and fed on fish and mollusks. The muscles which closed the jaw (and allowed it to "crunch") were very large, so it's also possible that Dorudon fed on small marine mammals as well. Dorudon teeth are heterodont, which means that teeth in different parts of the mouth look different. Modern toothed whales have homodont teeth (all teeth in the mouth are similar in shape). The largest tooth in a Dorudon's jaw are triangular and blade-like and toward the back of the jaw. The crowns are serrated (which make for easy slicing and cutting), and have two roots. Modern whale teeth have just one rounded slicing edge, and just one root.Dorudons had small brains, and were probably solitary creatures. They had a big hole in the lower jaw (like modern whales), which meant they could hear underwater. The jaw near this hole is very thin, just like in modern whales, too. Most likely sound waves would pass through the jaw and into a big pad of fat. This fat pad would then communicate the sound to the inner ear. But Dorudons lacked the "melon ball" inside the skull that modern whales have, so they could not echolocate.Dorudons had a very powerful spine, to which were attached very powerful muscles. They had a fluke, and probably swam like modern whales -- by using "caudal oscillations" (or side-to-side motions of the tail).Dorudon retained both its fore and rear limbs. The rear limbs were very small. The pelvis was not attached to the spine, and this means that Dorudon could not haul itself out on land like modern seals or walruses. (This leads scientists to the conclusion that it was fully a marine animal, and thus a true whale.)The forelimb is not so atrophied. The bones of the forearm are not as short as in modern whales, and Dorudon could still flex its elbow. (Modern whales have a fused elbow, and a stiff flipper.) The fingers, too, could also be flexed and were still mobile.Dorudons lived in warm seas all over the world. Fossils have been found in North America, Egypt, and Pakistan. There is possibly another species, "Dorudon serratus," found in South Carolina. But it is a juvenile and only partly complete and there is little scientific evidence that it is a separate species. Without further evidence, though, scientists have yet to collapse the two into a single species.