11/10/2022 0 Comments Black rhinocerosThe white rhinoceros, or square-lipped rhinoceros (Ceratotherium simum), is one of the five species of rhinoceros that still exist. Wide lips distinguish the white rhino, not skin color, which is similar to the black rhino The word "rhinoceros" is derived from the Greek words rhino, meaning nose, and keras, meaning horn hence "horn-nosed." Both African and Asian rhinos sleep in both standing and laying positions and both enjoy wallowing in muddy pools and sandy riverbeds. Both groups are herbivores and feed primarily on grass or branches depending on the species, some may eat more grass than branches. Both African and Asian rhinos are more active in the evening, night, and early morning, while spending the hot day time resting in the shade. However, the two groups have a lot of behavioral similarities. African rhinos feed low to the ground, whereas the Asian rhino browses on leaves that are higher up. African rhinos fight with their horns, using them to impale and throw their adversaries, while the Asian rhino fights with their bottom teeth, using them in a slashing motion. Behaviorally, it has been found that African rhinos are more aggressive than Asian rhinos. Morphologically, one obvious difference is that both African varieties have two horns in tandem while the Sumatran rhino has two horns, but one typically is a stub, and the other two Asian types have a single horn. The African and the Asian rhinoceros have some distinct characteristics. The collective noun for a group of rhinoceros is "crash." Most rhinoceros live to be about 50 years old or more. They have acute hearing and an excellent sense of smell, but poor eyesight over any distance. The canines and incisors are vestigial except for the lower incisors in Asian rhinos, which are developed into powerful slashing tusks. Rhinos have 24-34 teeth, mostly premolars and molars for grinding (dental formula 1-2/0-1, 0/1-1, 3-4/3-4, 3/3). There is a strongly developed occipital crest. The surface of the nasals where the horns sit is roughened. The nasal bones project forward freely and may extend beyond and above the premaxillae. These "horns" are not really true horns, but are epidermal derivatives, composed of a solid mass of thickly matted hair-keratin, a hair protein-that grows from the skull without skeletal support. Rhinoceros have one or two projections on the upper snout. Rhinos have an elongate skull, which is elevated posteriorly and a relatively small braincase for mammals this size (400-600g). The surviving species of rhinoceros have a thick protective skin, 1.5-5 centimeters thick, formed from layers of collagen positioned in a lattice structure. The largest known perissodactyl in the fossil record, an Asian rhinoceros called Paraceratherium, reached 11,000 kg (12 tons), more than twice the weight of an elephant. The family Rhinocerotidae is characterized by large size (one of the few remaining megafauna, animals whose average adult weight exceed 100 pounds or 44 kg, surviving today) with all of the species capable of reaching one ton or more in weight. Height comparison of extant rhinoceros species. The horses and tapirs both evolved in North America the rhinoceroses appear to have developed in Asia from tapir-like animals and then spread to the Americas during the middle Eocene (about 45 million years ago). By the start of the Eocene (55 million years ago), they had diversified and spread out to occupy several continents. The odd-toed ungulates arose in what is now North America during the late Paleocene, less than 10 million years after the dinosaurs died out. Tapirs have four toes on their front feet and three on their hind feet. In horses, only the third toe remains and supports the whole weight of the animal. In rhinoceroses, the first and fifth toes are lost and the animal walks on the remaining three toes. In the odd-toed ungulates, comprising the order Perissodactyla, the central axis of the foot passes through the third toe. There are only about 60 individuals left of the Javan rhinoceros. Only the white rhinoceros, which is listed as near-threatened, is no longer endangered. Four of the five species are either endangered or critically endangered. These mammals are all large, thick-skinned herbivores and have either one or two horns (actually thickly matted hair) on the upper snout.ĭespite adding to the human fascination with nature, in the twentieth century the rhinoceros has been hunted to the brink of extinction, often sought by hunters only for their horn. There are five surviving species, two of which are native to Africa and three to southern Asia. The rhinoceros (plural rhinoceros, rhinoceroses, or rhinoceri) or rhino is any of the odd-toed ungulates (order Perissodactyla) comprising the biological family Rhinocerotidae.
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