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May 21, 2007 · The fossil record demonstrates that mammals re-entered the marine realm on at least seven separate occasions. Five of these clades are still extant, whereas two are extinct. This review presents a brief introduction to the phylogeny of each group of marine mammals, based on the latest studies using both morphological and molecular data.
- Mark D. Uhen
- 144
- 2007
- 21 May 2007
The evolution of mammals has passed through many stages since the first appearance of their synapsid ancestors in the Pennsylvanian sub-period of the late Carboniferous period. By the mid- Triassic , there were many synapsid species that looked like mammals.
A rigorous test for the evolution of marine mammals would use many more species and more characters. But the general result holds: mammals made the transition to water at least three times: in pinnipeds (seals and walruses), in whales, and also in sirenians (dugongs and manatees).
- 1MB
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Although whales are expert swimmers and perfectly adapted to life underwater, these marine mammals once walked on four legs. Their land-dwelling ancestors lived about 50 million years ago. Meet Pakicetus , a goat-sized, four-legged creature that scientists recognise as one of the first cetaceans (the group of marine animals that includes ...
Oct 18, 2012 · I particularly appreciated the paleoecology section, as it showed how the evolution of marine mammals was deeply intertwined with the past positions of the continents, evolution of Earth’s oceans, and with other oceanographic factors like temperature, salinity, and productivity.
- Mark D. Uhen
- muhen@gmu.edu
- 2013
Mar 21, 2012 · When did scientists first propose that marine mammals evolved from land-living mammals? What findings led to this conclusion?
People also ask
How long did it take for marine mammals to evolve?
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A review of the broad outlines of what we know about the evolution of marine mammals from their fossil record, and then a focus on three discrete case studies that highlight important ecological transitions and evolutionary transformations that have occurred over the past 50 million years.
