The
orderMicroconchida 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.[1][2][3][4][5] 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.[6] All pre-Cretaceous "Spirorbis" fossils are now known to be microconchids.[6] 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.[3]
References
^Weedon, M.J. 1991. "Microstructure and affinity of the enigmatic Devonian tubular fossil Trypanopora". Lethaia 24:227-234.
^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.
^
abTaylor, 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.
Zaton, M., Wilson, M.A. and Vinn, O. 2012. "Redescription and neotype designation of the Middle Devonian microconchid (Tentaculita) species ‘Spirorbis’ angulatus Hall, 1861". Journal of Paleontology 86:417-424.