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Apr 16, 2009 · Cetaceans (whales, dolphins, and porpoises) are an order of mammals that originated about 50 million years ago in the Eocene epoch. Even though all modern cetaceans are obligate aquatic mammals, early cetaceans were amphibious, and their ancestors were terrestrial artiodactyls, similar to small deer.
- J. G. M. Thewissen, Lisa Noelle Cooper, Lisa Noelle Cooper, John C. George, Sunil Bajpai
- 2009
Meet Pakicetus, a goat-sized, four-legged creature that scientists recognise as one of the first cetaceans (the group of marine animals that includes dolphins and whales). How Pakicetus ' descendants evolved into whales is one of the most intriguing evolutionary journeys known to science.
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
Hippos likely evolved from a group of anthracotheres about 15 million years ago, the first whales evolved over 50 million years ago, and the ancestors of both these groups were terrestrial. These first whales, such as Pakicetus, were typical land animals. They had long skulls and large teeth that could be used for eating meat.
First came the ancestors of antelope, cats, giraffes, and rhinos. Later, around ten million years ago, North American mammals—camels, horses, and dogs—began to arrive.
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.
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Mar 21, 2012 · When did scientists first propose that marine mammals evolved from land-living mammals? What findings led to this conclusion?
