Microconchida

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.[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]

Microconchida
Temporal range:
Palaeoconchus angulatus (Hall, 1861) on a brachiopod from the Middle Devonian (Givetian) of Michigan
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Class: †Tentaculita
Order: †Microconchida
Weedon 1991
Genera
Helicoconchus elongatus, a microconchid from the Lower Permian of Texas. (See Wilson et al., 2011).
Punctaconchus midfordensis (Richardson, 1907). Bajocian, Clypeus Grit Member, Worgan's Quarry, Gloucestershire, UK.

References
  1. Weedon, M.J. 1991. "Microstructure and affinity of the enigmatic Devonian tubular fossil Trypanopora". Lethaia 24:227-234.
  2. 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.
  3. Vinn, O. 2010. "Adaptive strategies in the evolution of encrusting tentaculitoid tubeworms". Palaeogeography, Palaeoclimatology, Palaeoecology 292:211–221.
  4. Vinn, O. & Mutvei, H. 2009. "Calcareous tubeworms of the Phanerozoic". Estonian Journal of Earth Sciences 58:286-296.
  5. 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
  6. 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.
  • 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 56:785-791 doi:10.4202/app.2010.0086.
  • 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.
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