La Plata River Dolphin

Abstract

Whales, porpoises, and dolphins all belong to the order Cetacea (Latin for large sea creature). There are some 80–100 members of this order, the number being dependent on whether the taxonomist is a “lumper” or a “splitter.” Among the Cetacea there are two main subgroups, the toothed whales (Odontoceti), and the baleen whales (Mysticeti), and a fierce battle has raged among scientists in their efforts to decide whether these two groups came from one land mammal ancestor or whether each had its own progenitor. Resolving the question is particularly difficult as whale fossils are relatively sparse, but for the moment current opinion favors a monophyletic origin with separate lineages developing after these mammals took to the water. The word porpoise is derived from the Latin porcus (pig) and piscis (fish).