Invertebrate Diversity
Minor Phyla of Uncertain Relationship

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Characteristics

• Minute (<1 mm) unsegmented animals
• Body moderately elongated, somewhat flattened
• Epidermis with plates or spines
• Cilia on ventral surface
• Sensory bristles on head
• Typically have "bowling pin" shape: rounded head with slight neck constriction
• Many have a pair of posterior projections (caudal furca)
• In fresh water and marine sediments
• Phylogenetic relationships uncertain but may be related to Platyhelminthes