Incertae sedis: †Macurdablastus Blastoids (class Blastoidea) are an extinct type of stemmed echinoderm, often referred to as sea buds.

Like most echinoderms, blastoids were protected by a set of interlocking plates of calcium carbonate, which formed the main body, or theca.

Each ambulacrum had many long thin fine structures called brachioles, which were used to trap food particles and bring them to the mouth.

Like crinoids, blastoids were high-level stalked suspension feeders (feeding mainly on planktonic organisms) that inhabited clear-to-silty, moderately agitated ocean waters from shelf to basin.

The cover plates of the brachiolar groove were movable and could open, allowing food to enter, or close as needed.