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Species of the infraorder Cetacea A phylogenetic tree showing the relationships among cetacean families. [1]The evolution of cetaceans is thought to have begun in the Indian subcontinent from even-toed ungulates (Artiodactyla) 50 million years ago (mya) and to have proceeded over a period of at least 15 million years. [2]
Archaeoceti ("ancient whales"), or Zeuglodontes in older literature, is a paraphyletic group of primitive cetaceans that lived from the Early Eocene to the late Oligocene 1] Representing the earliest cetacean radiation , they include the initial amphibious stages in cetacean evolution , thus are the ancestors of both modern cetacean suborders ...
Aetiocetus is a genus of extinct basal mysticete, or baleen whale that lived , in the Oligocene in the North Pacific ocean, around Japan, Mexico, and Oregon, U.S. It was first described by Douglas Emlong in 1966 and currently contains known four species, A. cotylalveus, A. polydentatus, A. tomitai, and A. weltoni. [1]
Romaleodelphis was a medium sized toothed whale with long and slender jaws that make up about 71% of the total skull length. The animal was homodont, meaning that like most modern toothed whales and unlike several now extinct forms that coexisted with Romaleodelphis it possessed only a single type of tooth in its jaws.
They may be numerous, with some dolphins bearing over 100 teeth in their jaws. At the other extreme are the narwhals with their single long tusks and the almost toothless beaked whales with tusk-like teeth only in males. [20] In most beaked whales the teeth are seen to erupt in the lower jaw, and primarily occurs at the males sexual maturity. [21]
The whale's remains suggest it's a smaller relative of Basilosaurus cetoides, which lived along Alabama's coast 34-40 million years ago. ... When they found one of the creature's huge teeth, they ...
The fish range in size from about 3.83 inches to about 4.86 inches long, the study said. They were collected from between approximately 630 feet underwater to about 985 feet underwater.
The other two genera in the family, Gandakasia and Himalayacetus, are known only from teeth and mandibular fragments. [3] Retaining large hindlimbs, it was once thought that they could walk on land—indeed, their name means "walking whales"—, but recent research suggests they may have been fully aquatic like modern cetaceans, though the ...