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The traditional hypothesis of cetacean evolution, first proposed by Van Valen in 1966, [9] was that whales were related to the mesonychians, an extinct order of carnivorous ungulates (hoofed animals) that resembled wolves with hooves and were a sister group of the artiodactyls (even-toed ungulates). This hypothesis was proposed due to ...
Diversity in toothed and baleen whales. 33 Ma Evolution of the thylacinid marsupials . 30 Ma First balanids and eucalypts, extinction of embrithopod and brontothere mammals, earliest pigs and cats. 28 Ma Paraceratherium appears in the fossil record, the largest terrestrial mammal that ever lived. First pelicans. 25 Ma
Alpha keratin first evolves here; it is used in the claws of modern amniotes, and hair in mammals, indicating claws and a different type of scales evolved in amniotes (complete loss of gills as well). [20] Evolution of the amniotic egg allows the amniotes to reproduce on land and lay shelled eggs on dry land. They did not need to return to ...
In humans, the ventral joint of the pubic bones is closed. The most striking feature of evolution of the pelvis in primates is the widening and the shortening of the blade called the ilium. Because of the stresses involved in bipedal locomotion, the muscles of the thigh move the thigh forward and backward, providing the power for bi-pedal and ...
The whale was first mentioned in ancient Greece by Homer. There, it is called Ketos, a term that initially included all large marine animals. From this was derived the Roman word for whale, Cetus. Other names were phálaina (Aristotle, Latin form of ballaena) for the female and, with an ironic characteristic style, musculus (Mouse) for the male.
The larynx evolved when the first land vertebrates started breathing air and needed to separate food from air to prevent choking. Whales evolved from land mammals roughly 50 million years ago.
Whales evolved from land-living mammals, and must regularly surface to breathe air, although they can remain underwater for long periods of time. Some species, such as the sperm whale, can stay underwater for up to 90 minutes. [2] They have blowholes (modified nostrils) located on top of their heads, through which air is taken in and expelled.
An unusual journey. In her 26 years working with right whale sighting networks, Albert has seen right whales travel into the Gulf fewer than a half-dozen times.