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Cephalization in vertebrates, the group that includes mammals, birds, reptiles, amphibians and fishes, has been studied extensively. [4] The heads of vertebrates are complex structures, with distinct sense organs for sight, olfaction, and hearing, and a large, multi-lobed brain protected by a skull of bone or cartilage.
More than 99 percent of all species, amounting to over five billion species, [7] that ever lived on Earth are estimated to be extinct. [8] [9] Estimates on the number of Earth's current species range from 10 million to 14 million, [10] of which about 1.2 million have been documented and over 86 percent have not yet been described. [11]
The ASC's Stephen R. Edwards wrote Mammal Species of the World first and started Amphibian Species of the World second. Edwards decided to write about living amphibians because Richard G. Zweifel had just composed a large list of amphibian names and because experts from the University of Kansas were available to assist him.
The world’s frogs, salamanders, newts and other amphibians remain in serious trouble. A new global assessment has found that 41% of amphibian species that scientists have studied are threatened ...
The Chinese giant salamander (Andrias davidianus) is one of the largest salamanders and one of the largest amphibians in the world. [4] It is fully aquatic, and is endemic to rocky mountain streams and lakes in the Yangtze river basin of central China. It has also been introduced to Kyoto Prefecture in Japan, and possibly to Taiwan.
Additionally 1193 amphibian species (16% of those evaluated) are listed as data deficient, meaning there is insufficient information for a full assessment of conservation status. As these species typically have small distributions and/or populations, they are intrinsically likely to be threatened, according to the IUCN. [ 2 ]
The largest land mammal extant today is the African bush elephant. The largest extinct land mammal known was long considered to be Paraceratherium orgosensis, a rhinoceros relative thought to have stood up to 4.8 m (15.7 ft) tall, measured over 7.4 m (24.3 ft) long and may have weighed about 17 tonnes.
The species has a typical head–body length of 3.3–3.45 m (10.8–11.3 ft) and an average standing height of 1.4 m (4 ft 7 in) at the shoulder. [35] Hippos have barrel-shaped bodies with short tails and legs, and an hourglass-shaped skull with a long snout.