JENNIFER A. CLACK, a Reader in vertebrate paleontology and doctor of science at the University of Cambridge, has been studying tetrapod origins for 25 years.

克拉克是英国剑桥大学的科学博士与脊椎动物古生物学的高级讲师，研究四足动物起源已超过25年。

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Before long, the girl had swung around to my seat to demonstrate her double-jointed elbows and thumbs as well as a disturbingly loud clack in her jaw when she opened her mouth full bore.

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The slow deliberate clack of half a mile of wagons follows.

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At the time of his death Lt Clack was leading a patrol to the village of Dactran to discuss a meeting of elders planned for the next day.

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