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40 million years ago
- The earliest whales that we think were fully aquatic, that is, they never left the water, are found around 40 million years ago, during the middle Eocene. That means that the transition from terrestrial animals to fully aquatic animals took about 12 million years.
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May 21, 2007 · Evolution of marine mammals: Back to the sea after 300 million years. Mark D. Uhen. First published: 21 May 2007. https://doi.org/10.1002/ar.20545. Citations: 144. Sections. PDF. Tools. Share. Abstract. The fossil record demonstrates that mammals re-entered the marine realm on at least seven separate occasions.
Apr 16, 2009 · We focus on the evolution of cetacean organ systems, as these document the transition from land to water in detail. Cetaceans (whales, dolphins, and porpoises) are an order of mammals that originated about 50 million years ago in the Eocene epoch.
- J. G. M. Thewissen, Lisa Noelle Cooper, Lisa Noelle Cooper, John C. George, Sunil Bajpai
- 2009
Sep 24, 2014 · The basic hypothesis is that the early whale-like artiodactyls, like Indohyus and Pakicetus were land-based (terrestrial) mammals that spent most of their time near the water's edge. Over time, they adapted to the niches in the ocean.
Apr 16, 2015 · The movement of animals from the land into the sea has happened several times over the last 250 million years, and it has been documented in many different and singular ways.
Mar 21, 2012 · When did scientists first propose that marine mammals evolved from land-living mammals? What findings led to this conclusion?
Both morphological and molecular data tell us that the ancestors of the marine mammals were terrestrial, and that their various marine lifestyles have evolved independently at least seven times! Each lineage shows shared as well as unique evolutionary solutions to the challenges of living in water affecting their breathing, locomotion, feeding ...
