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A primitive group of Silurian to Permian jawed bony fishes, bearing bony spines in front of all but their caudal fins.
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European stage of the uppermost Lower Cretaceous, spanning the time between 107 and 95 million years ago.
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Photosynthetic, almost exclusively aquatic, nonvascular plants that range in size from simple unicellular forms to giant kelps several feet long. They have extremely varied life cycles and first appeared in the Precambrian.
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A coiled, chambered fossil shell of a cephalopod mollusk of the extinct order Ammonoidea.
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A microscopic, one-celled animal consisting of a naked mass of protoplasm.
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A relatively large opening on the last-formed chamber of a foraminiferal shell.
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European stage of the Lower Cretaceous, spanning the time between 114 and 107 million years ago.
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The middle era of Precambrian time, spanning the period between 3.8 and 2.5 billion years ago. Life arose on Earth during the early Archaean, as indicated by the appearance of fossil bacteria in rocks thought to be about 3.5 billion years old. Its name means "ancient."
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