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The traditional hypothesis of cetacean evolution, first proposed by Van Valen in 1966, [9] was that whales were related to the mesonychians, an extinct order of carnivorous ungulates (hoofed animals) that resembled wolves with hooves and were a sister group of the artiodactyls (even-toed ungulates). This hypothesis was proposed due to ...
The replacement in North America of a basal population of wolves by a more recent one supported the findings of earlier studies. [126] [134] [125] [129] There possibly existed a panmictic wolf population with gene flow spanning Eurasia and North America until the closing of the ice sheets.
South American foxes look like true foxes, despite being a unique canid genus more closely related to wolves and jackals. [60] Whales exhibit hyperphalangy—an increase in the number of phalanges beyond three phalanges-per-digit. Whales share this characteristic with extinct marine reptiles, but not present-day marine mammals. [61]
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 ...
The distribution of fossils in Indo-Pakistan, Africa, Europe, and North America suggests that this species preferred a warmer sea climate, preferably in the tropics. There is no commonly agreed ancestry of the whale, but they are thought to have evolved from an early group of carnivorous even-toed ungulates.
The limbs of more aquatic Eocene cetaceans did not preserve very well. Ambulocetus demonstrated that cetaceans swam by flexing the spine up and down (undulation) before they had evolved the tail fluke, forelimb propulsion evolved relatively late, and that cetaceans went through an otter-like phase with spinal undulation and hindlimb propulsion ...
Fossils have revealed an ancient marine reptile with a loosely connected jaw that allowed its throat to balloon out to a massive size so it could filter feed the way right whales do today.
The Beringian wolf became extinct, and the southern wolves expanded through the shrinking ice sheets to recolonize the northern part of North America. [23] [29] All North American wolves are descended from those that were once isolated south of the ice sheets. However, much of their diversity was later lost during the twentieth century due to ...