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Because there are no relatively complete limbs for archaic archaeocete cetaceans, it is not known how the transition in locomotory organs from land to water occurred. Recovery of a skeleton of an early fossil cetacean from the Kuldana Formation, Pakistan, documents transitional modes of locomotion, and allows hypotheses concerning swimming in early cetaceans to be tested. The fossil indicates that archaic whales swam by undulating their vertebral column, thus forcing their feet up and down in a way similar to modern otters. Their movements on land probably resembled those of sea lions to some degree, and involved protraction and retraction of the abducted limbs.<\/jats:p>","DOI":"10.1126\/science.263.5144.210","type":"journal-article","created":{"date-parts":[[2006,10,6]],"date-time":"2006-10-06T00:01:25Z","timestamp":1160092885000},"page":"210-212","source":"Crossref","is-referenced-by-count":139,"title":["Fossil Evidence for the Origin of Aquatic Locomotion in Archaeocete Whales"],"prefix":"10.1126","volume":"263","author":[{"given":"J. G. M.","family":"Thewissen","sequence":"first","affiliation":[{"name":"Department of Anatomy, Northeastern Ohio Universities College of Medicine, Box 95, Rootstown, OH 44272"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"S. 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