Squalodontidae closely related to the South Asian river dolphin ("Platanista gangetica"). The genus "Squalodon" was named by French naturalist Jean-Pierre Sylvestre de Grateloup in 1840 based on a jaw fragment he thought belonged to a reptile. Fossils discovered later, nevertheless, showed that this was a toothed whale. In extant odontocetes, however, the dentition is atavistic with all teeth reduced to simple, undifferentiated conical shapes. In squalodonts the teeth resemble those of the archaic whales, Archaeoceti, with conical incisors anteriorly and low-crowned, serrated teeth posteriorly. Squalodontidae Squalodontidae or the shark-toothed dolphins is an extinct family of large toothed whales who had long
Endangered species be in decline. Unlike their more general use elsewhere, the List uses the terms "endangered species" and "threatened species" with particular meanings: "Endangered" (EN) species lie between "Vulnerable" (VU) and "Critically Endangered" (CR) species, while "Threatened" species are those species determined to be Vulnerable, Endangered or Critically Endangered. The IUCN categories, with examples of animals classified by them, include: A) Reduction in population size based on any of the following: B) Geographic range in the form of either B1 (extent of occurrence) OR B2 (area of occupancy) OR both: C) Population estimated to number fewer than 2,500 mature individuals and