The prehistoric whale Cotylocara had a deep cavity in the top of its skull surrounded by a reflecting "dish" of bone, ideal for funneling tightly focused blasts of air; scientists believe it may have been one of the earliest cetaceans with the ability to echolocate. Mammalodon was a "dwarf" ancestor of the modern Blue Whale, which filters plankton and krill using baleen plates--but it's unclear whether Mammalodon's odd tooth structure was a one-shot deal, or represented an intermediate step in whale evolution. About 55 million years ago, at the start of the Eocene epoch, a branch of artiodactyls (the even-toed mammals represented today by pigs and deer) slowly veered off onto the evolutionary line that slowly led to modern whales. Even after all these years, Squalodon remains a mysterious beast--which can (at least partly) be attributed to the fact that no complete fossil has ever been found.

Zygorhiza (Greek for "yoke root"); pronounced ZIE-go-RYE-za See A heron soars overhead and lands in the reeds a safe distance away. You can gauge the measure of the prehistoric sperm whale Acrophyseter by its full name:

On the following slides, you'll find pictures and detailed profiles of over 20 Rivers have three distinct habitat areas: river bed, river banks, and the floodplain. Rodhocetus was a large, streamlined prehistoric whale of the early Eocene epoch that spent most of its time in the water--though its splay-footed posture demonstrates that it was capable of walking, or rather dragging itself along on, dry land. The early Eocene Pakicetus may have been the earliest whale ancestor, a mostly terrestrial, four-footed mammal that ventured occasionally into the water to nab fish (its ears, for example, weren't adapted to hearing well underwater). We simultaneously know a lot, and very little, about the ultimate ancestors of the Bottlenose Dolphin.

Zygorhiza ("yoke root") was closely related to Basilosaurus (see the previous slide), but possessed an unusually sleek, narrow body and hinged front flippers (a hint that this prehistoric whale may have lumbered up onto land to give birth to its young). - Julia M. Fahlke, Philip D. Gingerich, Roert C. Welsh & Aaron R. Wood - …

It's possible, though not proven, that the Mississippi-dwelling Teilhardina was North America's The Dinosaurs and Prehistoric Animals of Mississippi The importance of Aetiocetus lies in its feeding habits: this 25-million-year-old prehistoric whale had baleen alongside the fully developed teeth in its skull, leading paleontologists to infer that it fed mostly on fish but also filtered the occasional smaller crustaceans and plankton from the water. Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, Washington, DCDepartment of Paleobiology, National Museum of Natural History, Smithsonian Institution, Washington, DCUse the link below to share a full-text version of this article with your friends and colleagues.

Anatomical evidence for low frequency sensitivity in an archaeocete whale: Comparison of the inner ear of Zygorhiza kochii with that of crown Mysticeti The front limbs of Zygorhiza are actually very primitive in form because the elbow was still capable of being flexed.

First, here's the bad news: no dinosaurs have ever been discovered in Mississippi, for the simple reason that this state contains no geologic sediments dating to the Triassic or Jurassic periods, and was mostly underwater during the Over the course of 50 million years, beginning in the early Eocene epoch, whales evolved from their tiny, terrestrial, four-legged progenitors to the giants of the sea they are today. All groups exhibit aquatic adaptations directly related to feeding, particularly changes in the dentition and rostrum.