hd animal pictures 2013: Animal Pictures And Sounds

Saturday, 7 December 2013

Animal Pictures And Sounds

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They are distinguished by their zygodactylous feet; their separately mobile, stereoscopic eyes; their very long, highly modified, rapidly extrudable tongues; their swaying gait; and crests or horns on their distinctively shaped heads. Some species can change color, and many have a prehensile tail. Uniquely adapted for climbing and visual hunting, they are found in warm habitats that vary from rain forest to desert conditions—in Africa, Madagascar, and southern Europe, and across south Asia as far as Sri Lanka. They have also been introduced to Hawaii, California, and Florida, and are often kept as household pets.The oldest known chameleon is Anqingosaurus brevicephalus from the Middle Paleocene (about 58.7–61.7 mya) of China.

Other chameleon fossils include Chamaeleo caroliquarti from the Lower Miocene (about 13–23 mya) of the Czech Republic and Germany, and Chamaeleo intermedius from the Upper Miocene (about 5–13 mya) of Kenya.

The chameleons are probably far older than that, perhaps sharing a common ancestor with iguanids and agamids more than 100 mya (agamids being more closely related). Since fossils have been found in Africa, Europe and Asia, chameleons were certainly once more widespread than they are today. Although nearly half of all chameleon species today are found in Madagascar, this offers no basis for speculation that chameleons might originate from there.Monophyly of the family is supported by several studies.The feet of chameleons are highly adapted to arboreal locomotion, though species such as Chamaeleo namaquensis, that have secondarily adopted a terrestrial habit, have retained the same foot morphology with little modification. On each foot, the five clearly distinguished toes are grouped into two fascicles. The toes in each fascicle are bound into a flattened group of either two or three, giving each foot a tongs-like appearance. On the front feet, the outer, lateral, group contains two toes, whereas the inner, medial, group contains three. On the rear feet, this arrangement is reversed, the medial group containing two toes, and the lateral group three. These specialized feet allow chameleons to grip tightly onto narrow or rough branches. Furthermore, each toe is equipped with a sharp claw to afford a grip on surfaces such as bark when climbing. It is common to refer to the feet of chameleons as didactyl or zygodactyl, though neither term is fully satisfactory, both being used in describing totally different feet, such as the zygodactyl feet of parrots or didactyl feet of sloths or ostriches, none of which is significantly like chameleon feet. Although "zygodactyl" is reasonably descriptive of chameleon foot anatomy, their foot structure does not resemble that of parrots, to which the term was first applied. As for didactyly, chameleons visibly have five toes on each foot, not two.

Some chameleons have a crest of small spikes extending along the spine from the proximal part of the tail to the neck; both the extent and size of the spikes varies between species and individuals. These spikes help break up the definitive outline of the chameleon, which aids it when trying to blend into a background.All chameleons are primarily insectivores that feed by ballistically projecting their long tongues from their mouths to capture prey located some distance away. While the chameleons' tongues are typically thought to be one and a half to two times the length of their bodies (their length excluding the tail), smaller chameleons (both smaller species and smaller individuals of the same species) have recently been found to have proportionately larger tongue apparatuses than their larger counterparts.Thus, smaller chameleons are able to project their tongues greater distances than the larger chameleons that are the subject of most studies and tongue length estimates, and can project their tongues more than twice their body length.Although the Sanskrit word refers to dry land, it has been suggested that an Anglo-Indian interpretation led to its connotation as a dense "tangled thicket" while others have argued that a cognate word in Urdu did refer to forests.The term is prevalent in many languages of the Indian subcontinent, and the Iranian plateau, where it is commonly used to refer to the plant growth replacing primeval forest or to the unkempt tropical vegetation that takes over abandoned areas.One of the most common meanings of jungle is land overgrown with tangled vegetation at ground level, especially in the tropics. Typically such vegetation is sufficiently-dense to hinder movement by people, requiring that travelers cut their way through.This definition draws a distinction between rainforest and jungle, since the understorey of rainforests is typically open of vegetation due to a lack of sunlight, and hence relatively easy to traverse.Jungles may exist within, or at the borders of, rainforest in areas where rainforest has been opened through natural disturbance such as hurricanes, or through human activity such as logging.The successional vegetation that springs up following such disturbance of rainforest is dense and impenetrable and is a ‘typical’ jungle. Jungle also typically forms along rainforest margins, such as stream banks, once again due to the greater available light at ground level.Because European explorers initially travelled through tropical rainforests largely by river, the dense, tangled vegetation lining the stream banks gave a misleading impression that such jungle conditions existed throughout the entire forest. As a result it was wrongly assumed that the entire forest was impenetrable jungle.This in turn appears to have given rise to the second popular usage of jungle as virtually any humid tropical forest.Jungle in this context is particularly associated with tropical rainforest,but may extend to cloud forest, temperate rainforest and mangroves with no reference to the vegetation structure or the ease of travel.The word "Rainforest" has largely replaced "Jungle" as the descriptor of humid tropical forests, a linguistic transition that has occurred since the 1970s. "Rainforest" itself did not appear in English dictionaries prior to the 1970s.The word "Jungle" accounted for over 80% of the terms used to refer to tropical forests in print media prior to the 1970s.