Cetaceans are thought to have evolved during the Eocene (56-34 mya), the second epoch of the present-extending Cenozoic Era. Molecular and morphological analyses suggest Cetacea share a relatively recent closest common ancestor with hippopotami and that they are sister groups. [3] .

2009年4月16日 · We review raoellid artiodactyls, as well as the earliest families of cetaceans: pakicetids, ambulocetids, remingtonocetids, protocetids, and basilosaurids. We focus on the evolution of cetacean organ systems, as these document the …

2024年12月21日 · Cetaceans evolved from four-legged (quadruped) terrestrial animals, for which limbs played a primary role in movements, into virtually limbless aquatic creatures living in an environment where the back muscles are more important. Forelimbs are still present but are reduced to finlike flippers having shortened arm bones and no individual fingers.

2024年12月21日 · Cetacean - Marine Mammals, Evolution, Classification: Cetaceans are distant descendants of a group of poorly defined mammals known as condylarths. The first fossil cetacean, Pakicetus, is from the Early Eocene Epoch.

2012年3月21日 · How did these terrestrial ancestors morph over millions of years into the whales and dolphins we are so familiar with today? Dr. Mark Uhen answers questions about marine mammal evolution.

By the late Oligocene, the two modern lineages of cetaceans had evolved from archaeocete ancestors. Interestingly, the late Oligocene whale Aetiocetus , from Oregon, has skull and jaw features typical of baleen whales, and is considered to be the earliest mysticete — yet it also bore a full set of teeth.

The Cetaceans (whales, dolphins and porpoises) are mammalian marine descendants of land mammals. Their terrestrial origins are indicated by: Their need to breathe air from the surface; The bones of their fins, which resemble the limbs of land mammals

Cetaceans evolved convergently as streamlined swimmers with fish and aquatic reptiles. Molecular and morphological evidence suggests that artiodactyls as traditionally defined are paraphyletic with respect to cetaceans.

When the ancestors of living cetaceans–whales, dolphins and porpoises–first dipped their toes into water, a series of evolutionary changes were sparked that ultimately nestled these swimming mammals into the larger hoofed animal group.

2020年5月25日 · Extant cetaceans (whales, dolphins, and porpoises) and their extinct ancestors offer some of the strongest and best-known examples of macroevolutionary transition as well as microevolutionary adaptation.