Skeletal Evolution
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Cnidaria (Garcia)
Hydrozoa
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Anthozoa
Porifera (Frantin)
Demospongiae
Sclerospongiae
Hexactinellida
Mollusca (Coverly)
Gastropoda
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Annelida (Garcia)
Earthworms
Clam Worms
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Nematoda (Frantin)
Secernentea
Adenophorea
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Turbellaria
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Monogenea
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Chordata (Frantin)
Mammalia
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Chondrichthyes
Echinodermata (Coverly)
Holothuroidea
Ophiuroidea
Crinoids
Worksheet
Earthworms
A earthworm doesn't have a skeleton. It does have bristles on each segment known as setae that assist the earthworm in moving. Earthworms have no limbs. They have two sets of muscles: one that makes it long and thin, and one that makes it fat.