What is the evolutionary history of cetaceans?
cetces, derived from the Latin word for whale, "cetus", is a mammaline order that includes whales, dolphins and porpoises. HetAces are one of the four groups of mammals adapted to water life, the others are sirens (dugongs and manatees), Pinnipeds (seals and walruses) and water subfamily, Mustelids, Vydra. Like other water mammals, cetaceans evolved from earthly ancestors.
For many years, it has been a mystery how Cetacans developed like what they are today. This lasted until the discovery of the Group of Earth's Prot-Whales, then forty, in Pakistan in 1983. Then, then, forty, are the oldest well-known felt means that lives during the early Eocene, about 53 million years ago. Their fossils were dug in the Pakistan area, which was the coast to the ancient Tethys sea, the water formation associated with the world ocean and the most directly analogous Indian ocean.
Fortyids are considered to have only whales: specific location of earbones in the skull, folding in the middle ear bone and the way,as the peaks on the stools of the animal are arranged. These characteristics may seem Liwwke Menatiae, but they prove that then the thirty -aids were predecessors for whales. Then the forty -like ones were more closely similar to the wolves that are marked as a cetacean. Because their bones were found near what was once water, they were assumed that they were at least semi -aric.
It is assumed that some part of the fortyids have evolved on ambulocetis ("walking whales"), preferably an example of an almost completed fossil skeleton of "Ambulocetus Natans , a remarkable 3 m (10 ft)" long "mammals" (Transmission) (Transmission) (Transmission) (Transmission) (Transmission) (Transmission) (Transmission) (Transmission) (Transmission) (10 FT) (10 FT) (10 FT). Ambulocetides, also found in Pakistan, lived 50-49 million years. Obviously, the plunges were strongly water, even though he had his legs and could support his own weight on Earth. The tooth analysis showed that it could live in both fresh and salt water, and had a special adaptation to the ear that would allow it to hear well under the water. Look for Ambulocetus and see what it looks strange.
About the same period of time, protestis appeared. Processids, which means "early whales", were a complex, heterogeneous group. Fossils or fossil fragments of the Protcetides were found in Asia, Europe, Africa and North America. The promises were large, with stubborn legs and began to look more like today's cetaceans. Protcetus, one species, had a body similar to dolphin. It is not known whether this family had tail mobols as modern whales, because this part of the body is non -heletal and not fossilized well.
The first two groups of fully sea cetaceans were basilosaurides, including Basilosaurus - "King of Lizard," Fogs to think about the reptile when it was discoveredIn 1840, "Saurus" in the name - A Dorudon . Skeletons Basilosaurus , if 8 m (60 feet), were always considered before and were found in Egypt, Pakistan and the United States.
Basilosaurides eventually evolved into whales, as we know them today.