Basic configuration of our limbs appeared more than 400 million years ago, in fish

A discovery that changes the paradigm of limb evolution and the transition from fish to tetrapods

WASHINGTON - Dec. 1, 2016 - s4story -- Howard Associate Professor Rui Diogo and two postdocs of his lab, Julia Molnar and Borja Esteve-Altava, together with Peter Johnson from Auckland University made a remarkable discovery that changes the way the evolution of our limbs has been seen for centuries. This discovery was published in the end of November in the prestigious journal Scientific Reports, from the renowned Nature group.

Until now, scientists have assumed that the transitions from the configuration of the soft tissues of the limbs (including tissues such as muscles) of tetrapods (amphibians, reptiles and mammals) were dramatically different from their fish ancestors. That is, it was assumed that there was a sudden, paramount change from fins to limbs.

By undertaking dissections and MRI scans of the extant fishes that are more closely related to tetrapods - lungfish and coelacanths - these researchers re-examined the soft tissue anatomy of these fishes. Strikingly, their results, combined with previous data from studies of other living animals and of fossils, have shown that the characteristic configuration of the muscles and bones of tetrapods was already present more than 400 million years ago, in fishes. The only exception is the hand and foot structures, which have no clear correspondence with fish structures.
This discovery therefore shows that one of the major changes in animal evolution, the transition from fins to limbs, was actually a gradual, very slow process, and not a sudden, dramatic evolutionary step, as previously assumed.

This exciting discovery has therefore major implications not only for evolutionary biology in general and the origin of our limbs in particular, but also for a better understanding of the ecology and way of life of our closest fish relatives.

The paper is freely accessible at the Scientific Reports website:


Rui Diogo

Source: RuiDiogoLab

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