FactsheetSponges: The Trailblazers
Scientists believe sponges are the oldest animal phylum. They first appeared about 600 million years ago.
FactsheetCnidarians: The Polyp and Medusa
Scientists think that cnidarians were the first animals to have muscles and nerves to produce behavior.
FactsheetFlatworms: An Ancient Body Plan
Around 20,000 flatworm species today have the same basic body plan that appeared roughly 500 million years ago.
FactsheetAnnelids: Not Lowly, Lovely
Annelids are impressively adapted animals that live in every habitable niche on earth except the sky.
FactsheetMarine Arthropods: An Adaptive Body Plan
Marine arthropods are the most abundant group of animals in the ocean.
FactsheetTerrestrial Arthropods: Bold Explorers!
Arthropods were the first animals to venture out of the sea onto land all over the earth.
FactsheetMolluscs: Beauty and Diversity
The diversity of molluscs shows how a fleshy soft body plan can evolve into a variety of forms.
FactsheetEchinoderms: The Spiny Rebels
Modern echinoderms, which include sea stars, urchins, sea cucumbers and sea lilies, have a unique body plan with a five-part symmetry.
FactsheetChordates: This Is Us
The chordate phylum includes both invertebrates (without backbones) and vertebrates (with backbones).
The Cambrian Explosion was a burst of animal evolution that occurred in the ocean about 540 million years ago.