Question

Which of the following echinoderm animals belongs to class Crinoidea?
A. Sea urchin
B. Sea cucumber
C. Sea star
D. Sea lily

Answer 1

Hint: Echinoderm is a member of the genus Echinodermata of marine animals. Adults are recognized by their radial symmetry (usually five points) and include starfish, sea urchins, sand dollars and sea cucumbers, as well as water lilies or “stone lilies”. Mature echinoderms are found on the seafloor at all ocean depths, from the intertidal zone to the abyssal zone.

Complete answer:
Option A Sea urchin: Sea urchins are generally spiny, spherical, echinoderms of the class Echinoidea. Sea urchins move slowly, crawling on tubular legs and sometimes pushing each other with their spines. Sea urchins do not belong to the class Crinoidea.
Hence option A is not correct.
Option B Sea cucumber: Sea cucumbers are echinoderms of the class Holothuroidea. They are marine animals with skin like skin and an elongated body containing a single branched gonad. Sea cucumbers are found on the seabed all over the world. Since they do not belong to the class Crinoidea.
So, option B is also not correct.
Option C Sea star: Sea star or starfish are star-shaped echinoderms of the class Asteroidea. Common usage of these names also applies to ophiuroids, correctly called brittle stars or basket stars. Starfish are also called asteroids because they belong to the asteroidea class. Since they are not of class Crinoidea.
So, option C is not correct.
Option D Sea lily: Sea lily or Crinoids are marine animals that make up the class Crinoidea, one of the classes of the phylum Echinodermata, which also includes starfish, brittle stars, sea urchins, and sea cucumbers. Crinoids, in their adult form, are attached to the seafloor by a peduncle commonly known as a water lily, while the unstalked forms are known as feathered stars or comatulids.
Hence option D is the correct answer.

Therefore, Option D. Sea lily is the correct answer

Note:
Adult crinoids are characterized by a mouth located on the upper surface. This part is surrounded by the feeding arms and is associated with the U-shaped intestine, the anus resting on the mouth plate near the mouth. Although the basic pattern of the quintuple symmetry echinoderm can be discerned, in most cases of defects the five arms are subdivided into ten or more.