Key:  Class Scyphozoa

Phylum Cnidaria

Scyphozoans share the following characteristics:  Medusa form dominates the life cycle, and some do not have a polyp stage.  The medusae may be large, are often colored (often red, orange, or yellow), do not have a velum.  The margins of the bell are usually lobed into lappets and do not usually have a ring canal.  Sense organs are usually found in the notches between lappets.  The mouth is not usually on an extended manubrium.  The gut is divided into 4 branches by mesenteries.  Cnidae are present in both the epidermis and the gastrodermis.  Polyps, if present, are small and inconspicuous.  The polyps produce medusae by asexual budding (strobilization).

Key written by Dave Cowles
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Lower taxonomic levels Main Page Alphabetic Index Systematic Index Glossary
1a  Motile medusae, not attached to the substrate by a stalked adhesive disk which arises from the exumbrella 2
1b Sessile medusae, attached to the substrate by a stalked adhesive disk which arises from the exumbrella.   Order Stauromedusae
2a Medusa has a central mouth which arises from the subumbrella 3
2b Medusa has no central mouth.  Frilled edges of the oral lobes block mouth area.  Many tiny openings on 8 branching armlike appendages on the subumbrella open into gut.  Have no marginal tentacles. Order Rhizostomae
3a Bell of medusa taller than wide, divided into upper and lower region by a groove which circles the exumbrella.  Bell margin deeply scalloped into pedalia from which the tentacles, rhopalia, and lappets arise.  Small to moderate in size; mostly bathypelagic Order Coronatae
3b Bell of medusa may or may not be taller than wide, but is not divided into an upper and lower region by a groove circling the exumbrella.  Margin of bell often has lappets but is not deeply scalloped into pedalia.  The corners of the mouth are drawn out into four gelatinous, frilly lobes (oral arms).  Marginal tentacles are hollow and contain extensions of the radial canals.  Includes most of the common temperate and tropical jellyfish.  Mostly moderate to large in size. Order Semaestomae

Taxonomic Levels Represented in This Key:

  Order Semaestomae
  Order Stauromedusae

Page created by Dave Cowles, 2011
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