Crinoids: our favorite echinoderms!

Crinoids are sessile, filter-feeding benthic echinoderms restricted to marine environments.  They are the sister group to the other echinoderms, which include sea cucumbers, sea stars, and sea urchins.  Here is our current understanding of echinoderm evolution:

Echinoderm Tree

Drawn based on Baumiller, T.K., 2008, Crinoid ecological morphology. Annual Reviews of Earth & Planetary Sciences, 36:221-249. Dashed lines show the uncertainty concerning the evolutionary placement of brittlestars.

There are many scientists working to untangle the evolutionary relationships between echinoderms, a great place to follow the progress is the website created by the Echinoderm Tree of Life Project (EchinoTol) (http://echinotol.org/).

 

Modern crinoids are traditionally divided into those with and those without a stalk as adults.

Stalked crinoids (Sea lilies)
Stalked-06Stalked crinoids are currently restricted to depths greater than 100m.  There are approximately 100 described species.
 
 
 
 
 
Unstalked crinoids (Feather stars)
Oxycomanthus-07Featherstars begin their lives as stalked crinoids, then detach to become mobile juveniles and adults.  Many can crawl and some species are capable of swimming.  Featherstars represent the majority of modern day crinoid diversity and are found throughout the world’s oceans.  There are approximately 450 species described. 
Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s