Microconchida
Temporal range: Upper Ordovician - Middle Jurassic (Taylor and Vinn, 2006)
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.

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]

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. ^ a b 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. ^ a b 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.
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