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• Image Gallery
Nearly all the major animal groups living today appeared in the Cambrian Period, more than 500 million years ago. An “explosion” of life in Earth’s shallow seas included creatures with skeletons and other new features that would change the shape of life forever.
During the Ordovician Period about 50 million years later, the number of animal species gradually tripled. Life’s growing diversity reflected the animal groups to come, as everything in this period can also be connected to something living today.
Scientists learn about the animal groups that evolved during the Cambrian and Ordovician Periods through a number of specimens and fossils.
Continue to Poriferan (Sponges) & Cnidarian Images. >>
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