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The evolution of birds began in the Jurassic Period, with the earliest birds derived from a clade of theropod dinosaurs named Paraves. [1] Birds are categorized as a biological class, Aves. For more than a century, the small theropod dinosaur Archaeopteryx lithographica from the Late Jurassic period was considered to have been the earliest bird.
A turning point came in the early twentieth century with the writings of Gerhard Heilmann of Denmark.An artist by trade, Heilmann had a scholarly interest in birds and from 1913 to 1916, expanding on earlier work by Othenio Abel, [12] published the results of his research in several parts, dealing with the anatomy, embryology, behavior, paleontology, and evolution of birds. [13]
The fossil record of the area where mountain gorillas live is particularly poor and so its evolutionary history is not clear. [5] It was about 8.8 to 12 million years ago that the group of primates who were to evolve into gorillas split from their common ancestor with humans and chimps; this is when the genus Gorilla emerged.
The evolution of birds is thought to have begun in the Jurassic Period, with the earliest birds derived from theropod dinosaurs. Birds are categorized as a biological class, Aves. The earliest known species in Aves is Archaeopteryx lithographica, from the Late Jurassic period. Modern phylogenetics place birds in the dinosaur clade Theropoda.
Re-evolution of sexuality from parthenogenesis in orbitid mites. [52] Teeth in chickens. [53] Dewclaws in dogs. [44] Reappearance of wings on wingless stick insects [54] and earwigs. [44] Atavistic muscles in several birds [55] [56] and mammals such as the beagle [57] and the jerboa. [55] Extra toes in guinea pigs. [44] [58]
Gorillas are herbivorous, predominantly ground-dwelling great apes that inhabit the tropical forests of equatorial Africa. The genus Gorilla is divided into two species: the eastern gorilla and the western gorilla, and either four or five subspecies. The DNA of gorillas is highly similar to [[Human evolutionary genetics|that of humans
Birds evolved from certain feathered theropod dinosaurs, and there is no real dividing line between birds and non-avian dinosaurs except that some of the former survived the Cretaceous–Paleogene extinction event while the latter did not. For the purposes of this article, a 'bird' is considered to be any member of the clade Avialae. [1]
1933 – Nagamichi Kuroda publishes Birds of the Island of Java (2 Volumes, 1933–36). 1934 – Roger Tory Peterson publishes his Guide to the Birds, the first modern field guide. 1934–37 – Brian Roberts is the expedition ornithologist on John Rymill's British Graham Land Expedition (BGLE).