Microconchida

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

Microconchid on a brachiopod shell from the Potter Farm Formation (Middle Devonian, Givetian) in Alpena, Michigan.

Paleontology portal

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).

References

• Taylor, P.D. & Vinn, O. 2006. Convergent morphology in small spiral worm tubes ("Spirorbis") and its palaeoenvironmental implications. Journal of the Geological Society, London 163:225-228.

• Vinn, O. 2006. Two new microconchid (Tentaculita Bouček 1964) genera from the Early Palaeozoic of Baltoscandia and England. Neues Jahrbuch für Geologie und Paläontologie 2006:89-100.

• Vinn, O. 2010. Adaptive strategies in the evolution of encrusting tentaculitoid tubeworms. Palaeogeography, Palaeoclimatology, Palaeoecology 292:211–221.

• Vinn, O. & Mutvei, H. 2009. Calcareous tubeworms of the Phanerozoic. Estonian Journal of Earth Sciences 58:286-296.

• Weedon, M.J. 1991. Microstructure and affinity of the enigmatic Devonian tubular fossil Trypanopora. Lethaia 24:227-234.

• Wilson, M.A., Yancey, T.E. and Vinn, O. 2011. A new microconchid tubeworm from the Lower Permian (Artinskian) of central Texas, USA. Acta Palaeontologica Polonica (doi:10.4202/app.2010.0086).

• Zaton, M. & Vinn, O. 2011. Microconchids and the rise of modern encrusting communities. Lethaia 44:5-7 (DOI 10.1111/j.1502-3931.2010.00258.x)