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Figure 1:In mammals, the quadrate and articular bones are small and part of the middle ear; the lower jaw consists only of dentary bone.. While living mammal species can be identified by the presence of milk-producing mammary glands in the females, other features are required when classifying fossils, because mammary glands and other soft-tissue features are not visible in fossils.
Early in the Cenozoic, following the K-Pg event, the planet was dominated by relatively small fauna, including small mammals, birds, reptiles, and amphibians. From a geological perspective, it did not take long for mammals to greatly diversify in the absence of the dinosaurs that had dominated during the Mesozoic. [38]
This epoch featured a general warming trend that peaked at the Paleocene-Eocene Thermal Maximum, and the earliest modern jungles expanded, eventually reaching the poles. The oceans were dominated by sharks, as the large reptiles that had once ruled had become extinct. Mammals diversified rapidly, but most remained small.
The Triassic (/ t r aɪ ˈ æ s ɪ k / try-ASS-ik; sometimes symbolized 🝈) [8] is a geologic period and system which spans 50.5 million years from the end of the Permian Period 251.902 million years ago (), to the beginning of the Jurassic Period 201.4 Mya. [9]
The Eocene (IPA: / ˈ iː ə s iː n, ˈ iː oʊ-/ EE-ə-seen, EE-oh-[5] [6]) is a geological epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period in the modern Cenozoic Era.
Mass extinctions are characterized by the loss of at least 75% of species within a geologically short period of time (i.e., less than 2 million years). [18] [51] The Holocene extinction is also known as the "sixth extinction", as it is possibly the sixth mass extinction event, after the Ordovician–Silurian extinction events, the Late Devonian extinction, the Permian–Triassic extinction ...
The reason geologists didn’t declare the Anthropocene the start of a bigger and more important time measurement, such as a period, is because the current Quaternary Period, which began nearly 2. ...
The Neogene (/ ˈ n iː. ə dʒ iː n / NEE-ə-jeen, [6] [7]) is a geologic period and system that spans 20.45 million years from the end of the Paleogene Period 23.04 million years ago to the beginning of the present Quaternary Period 2.58 million years ago. It is the second period of the Cenozoic and the eleventh period of the Phanerozoic.