Hemichordates Chordate

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hemichordates ( half (½) chordates ) have features similar of chordates: branchial openings open pharynx , rather gill slits; stomochords, similar in composition notochords, running in circle round collar , ahead of mouth; , dorsal nerve cord—but smaller ventral nerve cord.


there 2 living groups of hemichordates. solitary enteropneusts, commonly known acorn worms , have long proboscises , worm-like bodies 200 branchial slits, 2.5 metres (8.2 ft) long, , burrow though seafloor sediments. pterobranchs colonial animals, less 1 millimetre (0.039 in) long individually, dwellings interconnected. each filter feeds means of pair of branched tentacles, , has short, shield-shaped proboscis. extinct graptolites, colonial animals fossils tiny hacksaw blades, lived in tubes similar of pterobranchs.








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