I did one on gigantic starfish a little while back-Click here to go see!!
1. The Gorgonocephalidae: The Basket Stars (incl. Gorgonocephalus spp.)
A family with arms that branch and branch and branch....until they form a huge "basket" with which they use for suspension feeding (see video above). The Gorgonocephalidae is a pretty big family (with some 55+ genera) distributed around the world.
Gorgonocephalus photo essay here.
Some basket stars, such as Gorgonocephalus have arms that will reach almost 2 to 3 feet across! Not all of them are this big but a lot of them are pretty sizeable....
2. Ophiopsammus maculata (New Zealand)
A member of the Ophiodermatidae, which are usually pretty small tropical beasts..but this one gets pretty big!
A disk that is about 2-3 inches across with an impressive arm span of over 6 to 7 inches!!
Its unclear how they feed but some suspect that they do something very similar to this!
3. Astrostoma agassizi (Antarctic: Southern Ocean)
Okay, so, I'm cheating. Because Astrostoma agasszi IS a member of the Gorgonocephalidae (see above).
I will probably write this up in more detail later but here's some quick details at this site:
Astrotoma is BIG. Disk is easily 2-3 inches across with correspondingly thick arms.
5. Ophiocoma aethiops (Baja California/Mexico)
All members of the genus Ophiocoma are tropical, shallow-water in all of the world's oceans and all of the species are pretty sizeable.
But for some reason, Ophiocoma aethiops from tropical East Pacific is just a bit bigger then the others species of Ophiocoma that one sees in the Indo-Pacific. There's more to this beast..but for now..just appreciate the fact that its a BIG one!
Honorable Mention: Stegophiura ponderosa
So, this is a deep-water species (at least 100-500 m) from off the west coast of North America, Japan, and Russia.
Unfortunately, very little is known about its biology. What does it do with all that heavy body mass?? Arms that don't really move out of one plane?? What do they eat??
How do we know so little about critters that are this frakkin' big????