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May 21, 2007 · Marine Mammal Diversity. Living groups of marine mammals vary greatly in their diversity. Rice (1998; Table 1 therein) reports that living Cetacea include 83 species in 39 genera; living Pinnipedia include 36 species in 21 genera; and Recent Sirenia include 5 species in 3 genera. Since then, several new species of cetaceans have been described ...
- Mark D. Uhen
- 144
- 2007
- 21 May 2007
Indeed, life had been evolving and changing for more than 3 billion years—the majority of the planet's existence—before the first creatures made their way out of the water. The first ocean lifeforms were microscopic, so small they would be invisible to the naked eye. Later, bizarre and alien-like creatures reigned supreme.
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
People also ask
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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.
- 1 Archaeoceti
- 2 Mysticeti
- 3 Odontoceti
The story of Cetacea began with the evolutionary radiation of placental mammals after the extinction of the dinosaurs and most large marine reptiles at the end of the Cretaceous about 66 million years ago (hereafter written Mya) (Fig. 2.1). The Paleocene (66–56 Mya) was the first epoch of the Cenozoic, a time when many placental mammals were small ...
Late Eocene Dorudontidae, the likely predecessors of early Mysticeti, had teeth to capture large or intermediate size prey, while modern Mysticeti use baleen to filter large numbers of small prey (see Sect. 8.1.1.1). Hence, there must have been a transitional phase from toothed Dorudontidae that used raptorial biting and intraoral suction to modern...
As with Mysticeti, late Eocene Dorudontidae were likely predecessors of early Odontoceti. However, they retained, to varying degrees, their adult dentition, although not necessarily for feeding. Some species continued to use teeth to capture small and intermediate-sized prey, but others evolved suction feeding and lost the functional use of teeth (...
- Randall W. Davis
- 2019
History of marine biology. HMS Challenger during its pioneer expedition of 1872–76. Marine biology is a hybrid subject that combines aspects of organismal function, ecological interaction and the study of marine biodiversity. [1] The earliest studies of marine biology trace back to the Phoenicians and the Greeks who are known as the initial ...
Most mammals on the African ark began to disappear around 20 million years ago, after Africa came into contact with the rest of the world again. But Africa wasn't the only ark.
