The eel-like body and scrawny "limbs" of the African lungfish would appear to make it an unlikely innovator for locomotion. But its improbable walking behavior, newly described by University of Chicago scientists, redraws the evolutionary route of life on Earth from water to land.
Extensive video analysis, published in the Proceedings of the National Academy of Sciences, reveal that the African lungfish can use its thin pelvic limbs to not only lift its body off the bottom surface but also propel itself forward. Both abilities were previously thought to originate in early tetrapods, the limbed original land-dwellers that appeared later than the lungfish's ancestors.
The observation reshuffles the order of evolutionary events leading up to terrestriality, the adaptation to living on land. It also suggests that fossil tracks long believed to be the work of early tetrapods could have been produced instead by lobe-finned ancestors of the lungfish.
"In a number of these trackways, the animals alternate their limbs, which suggested that they must have been made by tetrapods walking on a solid substrate," said Melina Hale, PhD, associate professor of Organismal Biology and Anatomy. "We've found that aquatic animals with fundamentally different morphologies and that aren't tetrapods could potentially make very similar track patterns."
Lungfish are a popular pet in the paleontological community, treasured for their unique evolutionary heritage.
"The lungfish is in a really great and unique position in terms of how it is related to fishes and to tetrapods," said Heather King, a graduate student and lead author of the study. "Lungfish are very closely related to the animals that were able to evolve and come out of the water and onto land, but that was so long ago that almost everything except the lungfish has gone extinct."
While anecdotes and rumors circulated within the scientific community about the alleg
|Contact: Robert Mitchum|
University of Chicago Medical Center