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Sunday 10 March 2013

Classification of Phylum Echinodermata


Phylum :- Echinodermata


Characters :- 


(i) Adult with radial & five rayed symmetry, while the larvae are bilaterally symmetrical.

(ii) The body is covered by calcareous ossicles or plates, often bearing projecting tubercles or spines.



SubPhylum :- Crinozoa


Characters :-


(i) Madriporite absent.

(ii) Radially symmetrical, possessing a cup shaped theca.



Class :- Crinoidea


Characters :-


(i) Arms are branched & bearing pinnules.

(ii) The ambulacral grooves radiates from the mouth & extend to the tip of the pinnules.


Examples :- Antedon (sea lily); Metacrinus;



Fig :- Antedon

Fig :- Metacrinus




SubPhylum :- Asterozoa


Characters :-


(i) Body is star shaped & remain unattached.

(ii) On the oral surface in the ambulacral groove, tube feet are present.



Class :- Asteroidea


Characters :-


(i) Arms are not sharply set off from the cetral dosc.

(ii) Anus & madriporite are present on the aboral surface.



Examples :- Asterias ; Asteropectin;



Fig :- Asterias













Class :- Ophiuroidea



Characters :-


(i) Arm sharply set off from the central disc.

(ii) Absence of ambulacral groove & arms are filled by vertebral ossicles.



Example :- Ophiura


Fig :- Ophiura











SubPhylum :- Echinozoa



Characters :-


(i) Radially symmetrical, globoid or discoid without arms or brachioles.

(ii) Madriporite & anus remain on the aboral surface.



Class :- Echinoidea


Characters :-


(i) Body more or less spherical, flattened orally/ aborally.

(ii) Aristotle's lantern, a apparatus used in feeding is mostly present.



Examples :- Echinus ; Arbacia;


Fig :- Echinus
Fig :- Arbacia












Class :- Holothuroidea



Characters :-


(i) Body elongated along oral/ aboral axis.

(ii) The surface of body may exhibit five ambulacral groove.



Examples :- Holothuria; Cucumaria;




Fig :- Holothuri


Fig :- Cucumaria











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