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Do Elephants Have Knees? And Other Stories of Darwinian Origins$
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Charles R., Jr. Ault

Print publication date: 2016

Print ISBN-13: 9781501704673

Published to Cornell Scholarship Online: January 2017

DOI: 10.7591/cornell/9781501704673.001.0001

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A Lungfish Walked into the Zoo

A Lungfish Walked into the Zoo

On the Origin of Limbs from Lobe-Fins

Chapter:
(p.76) 5 A Lungfish Walked into the Zoo
Source:
Do Elephants Have Knees? And Other Stories of Darwinian Origins
Author(s):

Charles R. Ault

Publisher:
Cornell University Press
DOI:10.7591/cornell/9781501704673.003.0005

This chapter discusses the origin of limbs from lobe-fins. The legacy of limb fossils tells of fins turning into feet in tandem with the history of swim bladders becoming lungs. Fish Is Fish by Leo Lionni hints at this story on two levels: tadpole becoming frog and fish whimsically imagining land animals as modified fish. From egg to birth, embryo development among many creatures resembles the transformation of tadpole to frog. The changes mirror steps along evolution's long journey from fish to people. This chapter first considers the African lungfish (Protopterus annectens) and its ball-and-socket girdles before explaining how a fish heart works. It also examines fossils that illustrate the path from lobe-fin to bony limb and concludes by looking at Tiktaalik, an intermediate between lobe-fins and tetrapods dated at 375 million years ago.

Keywords:   limbs, lobe-fins, fossils, lungs, fish, evolution, African lungfish, Tiktaalik, tetrapods

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