Head south hoofed
notoungulata
Extinct life in the ancient South American ungulates. 19th century, 30 years, cr Darwin river La Plata in Argentina discovered a number of important fossils, so well known of these early animals, but until the early 20th century it was officially named head south ungulates. This means that the southern continent-specific hoofed animals. Since most of the fossils found in South America, many people get used to South American ungulates on call.
South hoofed significant differences between the purpose of body size, can be as small as rabbits as big as rhinos. In general, smaller skull of these animals, there is always bubbling and location of a large artery and varied holes. Most of the teeth form a continuous tooth row; but in the progress or the members of the late expansion into the chisel-shaped incisors often, and in front of premolars have different degrees of degradation. Upper molars are generally triangular or square; lower molar-shaped bi-monthly, but always in the back inside of the cone - ridged teeth. Axial foot like every 5 or 3 toed feet; some species have claws.
Purpose of the South rise and fall of a hoof has gone through more than 5,000 years old. In the Cretaceous or later, they may have been ancestors of the ankle in the differentiation program out, but so far no intermediate links confirmed. See from the fossil has been found south of radiation and distribution of ungulates in the Cenozoic, the purpose of each period have changed. Initially, 5,500 years ago, before most members of the smaller size, low structure of the original crown. Although the number and types of small, but the distribution is very wide areas, such as Argentina, Brazil, Colombia, United States, China and Mongolia have their footprints, usually living in the hot semi-arid forest clearing. Dating back 500 million years ago to the Oligocene and Miocene, the South has reached the pinnacle of evolutionary purpose shoe. At this time, a wide range of structural characteristics of the majority of the members, figure increased to reduce the toes, teeth, the general trend of KK, and complex designs. Narrow geographical distribution. Since the Miocene, after the sharp decline in species; only remnants of the former on the verge of extinction a few genera. Some people think that most of the time in the Cenozoic, South America in isolation; only late in the third century, it may ditch by Boley and North America each Erhai have had contact from time to time. But this time, some ferocious carnivorous and progress Perissodactyla class mainland invasion from the north, the south has greatly affected the survival and development of ungulates.
Early 20th century found in North America, the North column beast, found in Mongolia and beast of ancient columns. In 1966, China's first column in the eastern Xinjiang, the beast that, after 30 years in succession in South China and Inner Mongolia to find a group like the original and ancient hoofed Fossil south. So far, China has been found in the Late Paleocene to Eocene, belonging to the North Branch of the 6 column is more than animal fossils, their morphology has a more primitive species than the same period of American nature. Vertebrate Paleontology in 1989, some U.S. scientists to classify animals newly created Head of North column.
Head south hoofed 14 families, 120 genera of existing fossils, are generally divided into the following four sub-projects. ① hoofed ancient South Asian projects. ② Type beast suborder. ③ Haig beast suborder. ④ Arrow tooth beast suborder. One view, advocated a South American hoofed groups of all 6 classes are attributed to a large unit, known as the South hoof head or over head. But this remains to be studied and discussed. |
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