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The origins and early evolution of primates is shrouded in mystery due to lack of fossil evidence. They are believed to have split from plesiadapiforms in Eurasia around the early Eocene or earlier. The first true primates so far found in the fossil record are fragmentary and already demonstrate the major split between strepsirrhines and ...
Basilosaurus, one of the first of the giant whales, appeared in the fossil record. 38 Ma Earliest bears. 37 Ma First nimravid ("false saber-toothed cats") carnivores — these species are unrelated to modern-type felines. First alligators and ruminants. 35 Ma Grasses diversify from among the monocot angiosperms; grasslands begin to expand.
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 ...
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.
Protocetus atavus ("first whale") is an extinct species of primitive cetacean from Egypt.It lived during the middle Eocene period 45 million years ago. The first discovered protocetid, Protocetus atavus was described by Fraas 1904 based on a cranium and a number of associated vertebrae and ribs found in middle Lutetian Tethyan marine limestone from Gebel Mokattam near Cairo, Egypt.
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. The ...
A baby monkey struggles and squirms as it tries to escape the man holding it by the neck over a concrete cistern, repeatedly dousing it with water. In another video clip, a person plays with the ...
The first fully terrestrial vertebrates were reptilian amniotes — their eggs had internal membranes that allowed the developing embryo to breathe but kept water in. This allowed amniotes to lay eggs on dry land, while amphibians generally need to lay their eggs in water (a few amphibians, such as the common Suriname toad, have evolved other ways of getting around this limitation).