| Microconchida Temporal range: Upper Ordovician - Middle Jurassic |
|
|---|---|
| Helicoconchus elongatus, a microconchid from the Lower Permian of Texas. (See Wilson et al., 2011) | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | incertae sedis |
| Class: | Tentaculita Bouček, 1964 |
| Order: | Microconchida Weedon, 1991 |
The Order Microconchida is a group of small, spirally-coiled, encrusting fossil "worm" tubes found from the Upper Ordovician to the Middle Jurassic (Bathonian) around the world (Weedon, 1991; Vinn, 2006, 2010; Vinn and Mutvei, 2009; Zaton and Vinn, 2011). 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 (Taylor and Vinn, 2006). All pre-Cretaceous "Spirorbis" fossils are now known to be microconchids (Taylor and Vinn, 2006). 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 (Vinn, 2010).