Microconchid
| Microconchida Temporal range: Upper Ordovician - Middle Jurassic (Taylor and Vinn, 2006) |
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| Palaeoconchus angulatus (Hall, 1861) on a brachiopod from the Middle Devonian (Givetian) of Michigan | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Mollusca (?) |
| Class: | †Tentaculita |
| Order: |
†Microconchida Weedon 1991 |
| Genera | |
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. They have lamellar calcitic shells, usually with pseudopunctae or punctae and a bulb-like origin. Many were long misidentified as the polychaete annelid Spirorbis until studies of shell microstructure and formation showed significant differences. All pre-Cretaceous "Spirorbis" fossils are now known to be microconchids. Their classification at the phylum level is still debated. Most likely they are some form of lophophorate, a group which includes phoronids, bryozoans and brachiopods. Microconchids may be closely related to the other encrusting tentaculitoid tubeworms, such as Anticalyptraea, trypanoporids and cornulitids.
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