Heavy jaws added to the placoderms' thuggish appearance, leading paleontologist John Long of Museum Victoria to compare the animals to "some gothic monster ... pretty awful and pretty strange." Long is one of the co-authors of the new study.
Long, a National Geographic Society grant recipient, also wrote Swimming in Stone, a recent book on placoderms found in Western Australia's Gogo formation. (National Geographic News is part of the National Geographic Society.)
The site of an ancient barrier reef, the Gogo formation has yielded a rich trove of well-preserved, three-dimensional marine fossils, including 25 placoderm species.
During an expedition to the area in 1986, Long found the original, 380-million-year-old fossils of a placoderm fish called Gogonasus—remarkable for its many features resembling those found on modern land animals. (Related story: "Ancient Fish Fossil May Rewrite Story of Animal Evolution" [October 18, 2006].)
He says the Gogonasus fish fossils "changed and revolutionized" our understanding of evolution.
Most people have the "Hollywood view of evolution," in which a fish morphs into an amphibian, followed by a reptile, then a mammal, then a primate, and finally a human, he said.
"But when we look at the Gogo fish, we see that so much of the human body plan is pushed back into the fishes. So that the origin of all our anatomical systems—90 percent of it—happened within fishes," he said.
"After the fishes left the sea and invaded the land, the rest was really fine-tuning of an existing pattern."
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