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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 quadrupedal locomotion.
Sir Wilfrid Le Gros Clark was one of the primatologists who developed the idea of trends in primate evolution and the methodology of arranging the living members of an order into an "ascending series" leading to humans. [7] Commonly used names for groups of primates such as prosimians, monkeys, lesser apes, and great apes reflect this methodology.
The order Primates consists of 505 extant species belonging to 81 genera. This does not include hybrid species or extinct prehistoric species. Modern molecular studies indicate that the 81 genera can be grouped into 16 families; these families are divided between two named suborders and are grouped in those suborders into named clades, and some of these families are subdivided into named ...
Primates range in size from the 30-gram (1 oz) pygmy mouse lemur to the 200-kilogram (440 lb) mountain gorilla. According to fossil evidence, the primitive ancestors of primates may have existed in the late Cretaceous period around 65 mya (million years ago), and the oldest known primate is the Late Paleocene Plesiadapis, c. 55–58 mya.
Old World monkeys are primates in the family Cercopithecidae (/ ˌ s ɜːr k oʊ p ɪ ˈ θ ɛ s ɪ d iː /). Twenty-four genera and 138 species are recognized, making it the largest primate family. Old World monkey genera include baboons (genus Papio), red colobus (genus Piliocolobus), and macaques (genus Macaca).
Traditionally, chimpanzees, gorillas and orangutans were grouped together, excluding humans, as pongids.Since Gray's classifications, evidence accumulating from genetic phylogeny confirmed that humans, chimpanzees, and gorillas are more closely related to each other than to the orangutan. [3]
According to molecular clock studies, the last common ancestor of all primates dates to around 79.6 mya, [3] although the earliest known fossil primates are only 54–55 million years old. [4] The closest relatives of primates are the extinct plesiadapiforms, the modern colugos (commonly and inaccurately named "flying lemurs"), and treeshrews. [3]
A phylogenetic tree, phylogeny or evolutionary tree is a graphical representation which shows the evolutionary history between a set of species or taxa during a specific time. [ 1 ] [ 2 ] In other words, it is a branching diagram or a tree showing the evolutionary relationships among various biological species or other entities based upon ...