Distant Relatives: Paddlefish  

Thursday, May 24, 2007

Carl Zimmer has an article up titled Old Hands and New Fins at The Loom. In it he explains how humans are more closely related to an odd fish than was previously thought.

Back 400 million years ago, our ancestors swan with fins. The descendants of those early fish split off into two main branches. One became the ray-finned fishes--a group that makes up the vast majority of fish alive today. The other, sometimes called the lobefins, produced many species, but only three lineages of lobefins survive today. One is the coelacanths, which survive in a few isolated spots in the Indian Ocean. One is the lungfishes, which struggle against extinction in rivers and ponds in Australia, Africa and South America. The third lineage is by far the most successful: the fish with feet, or also known as the tetrapods. Tetrapods include amphibians, reptiles, and mammals. We belong to their ranks.

In that way, paddlefish branched off ray-finned fish. Scientists studying the fins of paddlefish have found that their limbs have the same pattern expressed in the late stages as humans. While their limbs continue growing into fins, the bones resemble a stage between fish fins and the limbs of land-dwelling animals.

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