The order Microconchida is a group of small, spirally-coiled, encrusting fossil "worm" tubes from the class Tentaculita found from the Upper Ordovician to the Middle Jurassic (Bathonian) around the world.

Many were long misidentified as the polychaete annelid Spirorbis until studies of shell microstructure and formation showed significant differences.

Microconchids may be closely related to the other encrusting tentaculitoid tubeworms, such as Anticalyptraea, trypanoporids and cornulitids.

While there is a consensus that they were present in the seas and in brackish water, there is a debate about their presence in freshwater.

[9][10] A recent review of the associated fauna failed to find reliable occurrences of microconchids in the Middle Devonian to Early Permian time interval because microconchids seem to co-occur with other signs of marine influence,[11] such as xiphosurans and chondrichthyan egg capsules.