Word: fishapod
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Dates: during 2006-2006
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...propping the animal's head above the water so that it could survey its surroundings or for anchoring it underwater as it waited to ambush its prey. The advantage of being able to gulp air through lungs as well as gills would likewise have been immediate, given that the fishapod made its home in warm, shallow waters that were frequently rendered inhospitable by decaying vegetation...
...fishapod was among the pioneering organisms to take advantage of an ecological frontier--the marshy floodplains of large rivers--that opened between 410 million and 356 million years ago during the Devonian period, known as the Age of Fishes. Early in the Devonian, the continents were mostly masses of bare rock with just a fringe of plants "no taller than your ankle," as Daeschler puts it, growing along the wet margins of rivers and streams. By the late Devonian, however, thick vegetation had taken hold in marshes, fens and floodplains, and mosses, ferns and trees had coalesced into the world...
...formed the basis of a new food chain. Bacteria, fungi and small arthropods (the animal group that includes crustaceans and insects) moved in to feed on the debris; small fish moved in to eat the arthropods; bigger fish moved in to eat the small fish. Among them were the fishapod's lobe-finned ancestors, which found in the vegetation-clogged shallows abundant food and relative safety from predators...
Because characteristics like limb development are governed by powerful families of genes known as Hox genes, the fishapod's curious mix of features intrigues developmental biologists as much as it does paleontologists. Recent experiments on mice by University of Geneva geneticist Denis Duboule and his colleagues, for example, show that Hox genes control limb development in two stages. "Even though the same genes are involved," says Duboule, "separate processes govern the development of arms and legs and the development of hands and feet...
...version of that switch too. For example, Zebrafish (ray-finned fish that split off from the lineage that led to lobe-fins early in the Devonian) have only part of the sequence, whereas coelacanths (lobe-fins closely related to lungfish) have a lot more of it. And the fishapod, presumably, had even more...