Echinoderms Flashcards
Echinoderms General Info
Cambrian to recent
Deuterostomes
Many have 5 fold symmetry
Variety of lifestyles - but not free swimming
Tube feet in rows - supported by ambulacra
Water powered vascular system
Water taken through madreporite - connected to stone canal and then to feet
Helicoplacoid
Middle to late Cambrian
Irregular, radial body arrangement
Plates not fused, disarticulate easily
Homalozoa
Middle Cambrian to late Carboniferous
Bilaterally symmetrical
Mouth at base of appendage
Filter feeders
Basal chordates (?)
Blastozoa
Early Cambrian to Permian
Globular, tightly sutured calyx/thecae
No arms - brachioles
Stem made of columnals
Competed with Crinoids for food
Blastoids
Ordovician to Permian - peak in Miss.
Pentameral symmetry - reduced plates
Typically short
Cystoids
Ordovician to Devonian
Spherical / sac like theca
Could be stalked
Eocrinoids
Cambrian to Silurian
Early stalked echinoderm
High variety of theca and holdfasts
Crinozoa - Sea Lilies
Cambrian to recent - peak in Miss.
Crinoidea + paracrinoidia
Long erect arms - could have branches
Stems made of columnals (cirri) connect to sea floor
Found in deep sea and coral reef - could have helped developed reefs
Found upside down on driftwood
Asterozoa - Starfish
Late Cambrian to recent
Starshaped bodies
Benthic life mode
Open water vascular system
Asteroidea
Ordovician to recent
5 - 25 arms
Durophagous - contributed to the marine Mesozoic revolution - eats barnacles, bivalves, other echidnoderms
Each arm has an ambulacral groove
Ophiuroidea - Brittle Stars
Ordovician to recent
Typically filter feeders
Holothuroidea - Sea Cucumbers
Middle Cambrian to recent
Free living
Elongate + flexible body
Five rows of tube feet - no ambulacral grooves
Microscopic sclerites in the body wall - skeleton
Regular Echinoidea - Sea Urchins
Late Ordovician to recent
More globular shape
Anus on top of test
Long spines, single crystal
Irregular Echinoidea - Sand Dollars
Early Jurassic to recent
Elongate test - anus on the outside
Ambulacra form petal shapes
Only sand dollars have an Aristotle’s Lantern
Reduced spines - fuzzier
Buried themselves in sediment
