Astrocladus socotrana, a basket star from the western Indian Ocean. LOVE the bumpy spines! #echinoday

And the other side! The jaw of the urchin sticking through the even more complicated plates around the mouth! Jaw used to feed on prey and other items! #echinoday Cidaris rugosa

A cidaroid sea urchin skeleton (aka a test) no spines. Showing off the top-including the anus and all of the plates around it.. as well as their madreporite or sieve plate. #echinoday Cidaris rugosa

Clypeaster euclastus! A sand dollar with a curiously bulged petaloid giving it a very UFO like appearance! #echinoday

The first described specimen (ie holotype) of Ophiura monaria now known as Amphiophiura insolita from the Hawaiian region. A deepsea species that shows off very distinct plates! #echinoday

The lovely test of the deep-sea urchin Gracilechinus gracilus! Spines removed, showing off where they articulate, pores where tube feet emerge and etc! #echinoday

Same genus, Goniocidaris-but spines look like umbrellas! YOW. More from the MNHN in Paris #echinoday

and even MORE Goniocidaris! From the South Pacific somewhere I think..but yeah, spines are unreal! What are the crazy shapes/morphologies for? Your guess is as good as mine! #echinoday from collections of MNHN Paris!

Another cidaroid urchin with crazy spines.. Goniocidaris magi from New Zealand (IZ collections NMNH)! Spine function suggest may possible interpretations-defense among the choices..but we don't know for sure! #echinoday

The bizarre wing-like spines on the cidaroid urchin Cidaris blakei from the tropical West Atlantic! What are they for? (red color is from survey stain) Cidaroids have been around for hundreds of millions of years. They're doing something right! #echinoday