Leatherback sea turtle million years ago during the Cretaceous period. The dermochelyids are relatives of the family Cheloniidae, which contains the other six extant sea turtle species. However, their sister taxon is the extinct family Protostegidae that included other species that did not have a hard carapace. Leatherback turtles have the most hydrodynamic body design of any sea turtle, with a large, teardrop-shaped body. A large pair of front flippers powers the turtles through the water. Like other sea turtles, the leatherback has flattened forelimbs adapted for swimming in the open ocean. Claws are absent from both pairs of flippers. The leatherback's flippers
Varieties of Chinese their own standard languages. In China, however, Literary Chinese maintained its monopoly on formal writing until the start of the 20th century. The logographic writing, read with varying local pronunciations, continued to serve as a source of vocabulary and idioms for the local varieties. The new national standard, Vernacular Chinese, the written counterpart of spoken Standard Chinese, is also used as a literary form by speakers of all varieties. Dialectologist Jerry Norman estimated that there are hundreds of mutually unintelligible varieties of Chinese. These varieties form a dialect continuum, in which differences in speech generally become more pronounced as distances