Editing Echinoderm (section)

==Diversity==

There are about 7,600 [[extant taxon|extant]] species of echinoderm as well as about 13,000 known extinct species.<ref name=Tree/><ref name="adw">{{harvnb|U. of Michigan Museum of Zoology}}</ref> All echinoderms are [[Marine biology|marine]], but they are found in habitats ranging from shallow intertidal areas to abyssal depths. Five extant classes of echinoderms are generally recognized: the Asteroidea ([[starfish]], with over 1900 species), Ophiuroidea ([[brittle stars]], with around 2,300 species), Echinoidea ([[sea urchin]]s and [[sand dollar]]s, with some 900 species), Holothuroidea ([[sea cucumber]]s, with about 1,430 species), and Crinoidea ([[feather star]]s and [[Sea lily|sea lilies]], with around 580 species).<ref name="Uthicke">{{harvnb|Uthicke|Schaffelke|Byrne|2009}}</ref><ref name="Arnone Byrne Martinez 2015">{{harvnb|Arnone|Byrne|Martinez|2015}}</ref>

<gallery mode=packed caption="The extant classes of echinoderms">

File:Ophionereis reticulata 1.jpg|A brittle star, ''[[Ophionereis reticulata]]''
File:Sea cucumber at Pulau Redang.jpg|A [[sea cucumber]], ''[[Stichopus chloronotus]]'', from Malaysia
File:Nerr0878.jpg|Starfish of varied colours
File:Strongylocentrotus purpuratus 1.jpg|A sea urchin, ''[[Strongylocentrotus purpuratus]]''
File:Crinoid on the reef of Batu Moncho Island.JPG|[[Crinoid]] on a [[coral reef]]
</gallery>