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The First Breath

Image of lungfish ribs

The cranial ribs in the Australian lungfish Neoceratodus forsteri are needed to anchor the pectoral girdle, allowing the fish to raise its head to gulp air. Image adapted from Johanson et al. 2005.

By Alice Clement

A new fossil find shows that a global decline in oxygen millions of years ago drove the evolution of air-breathing in lungfishes.

Alice Clement is a PhD student at the Research School of Earth Sciences of the Australian National University and Museum Victoria, where she is studying lungfish evolution and anatomy.

The full text of this article can be purchased from Informit.

Most people enjoy a dip in the ocean at their local beach or favourite holiday spot, but if you lived during the Devonian you might think twice before taking the plunge.

The Devonian Period, 416–359 million years ago, is known as the Age of Fishes. Life in the seas was very different to what we know today. The waters teemed with a plethora of beasts, including huge armoured placoderm fishes and early sharks and bony fishes. Nautiloids floated by while trilobites (ancient arthropods) scuttled around beneath them.

At this time, some fishes were invading near-shore and freshwater habitats, perhaps to escape the dangerous Devonian seas. Others, such as the early tetrapods, were beginning to venture onto dry land.

Migrating out of the water and onto solid earth was no easy feat. These animals would have faced new challenges relating to locomotion, regulation of water content and respiration.

The tetrapods were not the only ones using lungs instead of gills. Lungfish, our closest surviving piscine relatives, independently developed the ability to breathe air during the Devonian Period. Lungfish surviving today inhabit freshwater territories, and lungfish fossils thought to have been air-breathers have all originated from swamps, lakes and river deposits (i.e. freshwater environments).

Warm, stagnant, tropical swamps were long thought to be...

The full text of this article can be purchased from Informit.