Until now, the only fossils of Tiktaalik researchers had examined were of its front parts. To find out more about the fish, researchers investigated additional blocks of rock recovered from the dig site where Tiktaalik was discovered. Although some of these blocks were first dug in 2004, researchers did not look at them more closely until recently, mainly because the blocks did not seem to contain much bone. Moreover, it took years to carefully and properly remove the rock surrounding the fragile fossils.
The scientists discovered the back part of Tiktaalik.This made a direct comparison of the front and back appendages of the animal possible. Unexpectedly, the researchers found Tiktaalik had big, strong pelvic(胃盆)bones with similarities to early tetrapods.
"I was expecting to find a diminutive back fin and pelvis," study lead author Neil Shubin, a paleontologist at the University of Chicago, told LiveScience. "Seeing the huge pelvis set me back a bit-I looked at it again and again, because I was quite surprised."
Shubin cautioned that Tiktaalik is not the ancestor of all limbed vertebrates. It is currently the closest known relative, "but not the only, direct ancestor," he said. "It is more like our closest cousin."
63.According to the passage, previous findings show that_.
A. the evolution of back limbs happened under the water
B. the ancestors of limbed animals could walk underwater
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