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Ambulocetus
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Only known specimen of Ambulocetus. Note poor preservation of limb bones,
pelvis, and snout. The scapula and humerus are unknown even from fragments.
(Full-size Image) Source: Thewissen Lab website.
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Ambulocetus, which means "walking whale," is the name given to a creature that has been widely accepted as an ancestor of whales. It lived about 50 million years ago, during the early Eocene. This animal is known, however, solely from a single, partial skeleton, that of an individual about 3 meters (~10 feet) long (see figure at right; to view a high resolution image, click here).
The specimen was found in eastern Pakistan by a team led by anatomist Johannes Thewissen (Northeastern Ohio University College of Medicine), who popularized the idea that this creature was an early, amphibious ancestor of whales. The actual evidence for such a claim is actually rather meager. Here are the few points usually cited in support of this assertion:
Ode to Anbulocetus
by Gene McCarthy
Ambulocetus was a whale
Ambulocetus had no tail.
But he had legs, and he had feet,
(Though his bones are incomplete).
No flippers had he, nor a fluke,
And yet this earns him no rebuke.
He couldn't spout. He didn't swim.
Perhaps he's just some scholar's whim.
Was he a true ungulate?
Or did someone bungle it?
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It is supposedly whalelike because it had a nose that allowed it to swallow underwater. However, human beings and many other non-marine organisms can swallow underwater. Moreover, as can be seen figure above (to view a high resolution image, click here), the snout of the single known specimen was not preserved.
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The periotic bone, which surrounds the inner ear in mammals, is supposedly whalelike, allowing ambulocetids to hear well in water. But no one actually knows how well these creatures could hear, whether in water or out of it. Moreover, little or nothing is usually said about the great dissimilarity between all of the other features of this animal and those of a whale.
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Its teeth are alleged to be like those of a whale. But the jaws of the single individual known (again see the figure above, click here to enlarge) are highly fragmented, and the few teeth preserved appear to differentiated, unlike those of toothed whales.
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It is asserted that Ambulocetus's hindlimbs were ill-adapted to terrestrial locomotion. But the limbs — and the pelvis — are so poorly preseved (see high resolution image), that it seems there is no clear evidence bearing on this point.
Copyright &169; 2011 Macroevolution.net
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