Cartoon depictions of the first animals to emerge from the ocean and walk on land often show simple fish with feet venturing onto land. But Jennifer Clack, a paleonto-logist at the University of Cambridge who has studied the fossils of these extinct creatures for more than two decades, says the earliest land vertebrates -- also known as tetrapods -- were more diverse than we could possibly imagine.
Artist's depiction of the tree-of-life for early tetrapods, showing 100 million years of palate evolution and diversification with the outer edges of the diagram representing the diversity of palate size and shape (artwork by Brian Sidlauskas).
“Some looked like crocodiles, some looked like little lizards, some like moray eels, and some were snake-like,” Clack said. “They occupied all sorts of niches and habitats. And they varied tremendously in size -- from about four inches (10 cm) long to 16 feet (5 meters).”
Long before mammals, birds, and dinosaurs roamed the Earth, the first four-legged creatures took their first steps onto land and quickly inhabited a wide range of ter-restrial environments. These early land vertebrates varied considerably in size and shape, Clack added.
“One of the big questions at the moment is, Where did modern amphibians come from?” Clack explained. “One of the hypotheses is that they have evolved by paedomorphosis and miniaturization from early tetrapods. This study lends weight to that idea.”
The team's results will be detailed in the July 16, 2009 online issue of the Journal of Anatomy. More>>
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