Author: Carolyn Gramling / Source: Science News
The cradle of vertebrate evolution was limited to a zone of shallow coastal waters, no more than 60 meters deep.
In those waters, fish — the first vertebrates — appeared roughly 480 million years ago, a study finds. For nearly 100 million years, those creatures rarely strayed from that habitat, where they diversified into a dizzying array of new forms, scientists report in the Oct. 26 Science. The study resolves a long-standing mystery about where our earliest backboned ancestors arose.
Scientists have long debated whether the animals appeared first in the shallows or the deep, or in fresh or salty water. “The main problem is that the fossil record [of vertebrates] is absolutely terrible for the first 50 million to 100 million years of their existence,” says paleobiologist Lauren Sallan of the University of Pennsylvania. “And when [there are] fossils, they’re in tiny pieces. It’s hard to tell what exactly’s going on.”
So Sallan and her colleagues amassed 2,827 fossils of jawed and jawless fishes that lived between 480 million and 360 million years ago. To that database, the team added information on the environments that the creatures lived in — such as shallow coastal water, freshwater or the deeper ocean — based on both the geology of the rocks the fossils were…
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