Kirengellida

The Kirengellids are a group of problematic Cambrian fossil shells of marine organisms. The shells bear a number of paired muscle scars on the inner surface of the valve.

Kirengellida
Temporal range:
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Brachiopoda (?)
Order: †Kirengellida
Family: †Kirengellidae
Rozov 1975

These fossils have conventionally been regarded as monoplacophoran molluscs, and possibly ancestral to gastropods or cephalopods.[1] They were presumed to be exogastric on the presumption that their larger muscle scars were anterior,[2][3] but it may be dangerous to compare these scars with molluscan musculature.[4] In any case, they coiled in the opposite direction to Romaniella.[4] However, their calcitic shells, the position of the muscle scars, and putative association with secondary shell elements, make a brachiopod affinity possible, by analogy with the mobergellans: a group of phosphatic shells from the same time period, with a similar set of muscle scars.[4] There is also strong similarity to the contemporary brachiopod group, the Craniopsids. In the case of this diagnosis, a simple lophophore apparatus is postulated to sit between the muscle scars and the edges of the shell.[4] On the other hand, Vendrasco (2012) reaffirmed the interpretation of the kirengellids as molluscs, noting that the Kirengella muscle scar pattern is also similar to what occurs in monoplacophorans.[5][6] Bouchet et al. (2017) classified Kirengellida as an order within the subclass Tergomya.[7]

Included taxa

After [4]: fig. 5 

  • Kirengella Rozov, 1968 (Upper Cambrian)
    • † Kirengella alta Whitfield 1889
    • Kirengella ayaktchica - type species
    • Kirengella expansus
    • † Kirengella kultavasaensis Doguzhaeva 1972
    • Kirengella oregonensis
    • Kirengella pyramidalis
    • † Kirengella rectilateralis Berkey 1898
    • † Kirengella stabilis Berkey 1898
    • Kirengella washingtonense
  • Hypseloconus (Upper Cambrian)
  • Lenaella (Tremadoc / Lower Ordovician)
  • Nyuella (Tremadoc / Lower Ordovician)
  • Romaniella (Arenig / late Lower Ordovician)
  • Moyerokania (Arenig / late Lower Ordovician)
  • Angarella (Arenig / late Lower Ordovician)
  • Pygmaeoconus (Llanvirn / early Middle Ordovician)

References
  1. e.g. Yochelson, E. L.; Flower, R. H.; Webers, G. F. (1973), "The bearing of the new Late Cambrian monoplacophoran genus Knightoconus upon the origin of the Cephalopoda", Lethaia, 6 (3): 275–309, doi:10.1111/j.1502-3931.1973.tb01199.x
  2. Yochelson, E.L. (1978). "An alternative approach to the interpretation of the phylogeny of ancient mollusks". Malacologia. 17 (2): 165–191.
  3. Yochelson, E.L; Webers, G.F. (2006). "A restudy of the Late Cambrian Molluscan fauna of Berkey (1898) from Taylors Falls, Minnesota" (PDF). Minnesota Geological Survey Report of Investigations. 64: 60.
  4. Dzik, Jerzy (2010). "BRACHIOPOD IDENTITY OF THE ALLEGED MONOPLACOPHORAN ANCESTORS OF CEPHALOPODS" (PDF). Malacologia. 52 (1): 97–113.
  5. Vendrasco, M. J. (2012). "Early evolution of molluscs". In Averkii Fyodorov; Havrila Yakovlev (eds.). Mollusks: Morphology, Behavior and Ecology. Nova Science Publishers. pp. 1–43. ISBN 9781621009870.
  6. Cope, J. C. W.; Ebbestad, J. O. R. (2023). "Tergomyan molluscs from the Early Ordovician of the Llangynog Inlier, South Wales, UK". PalZ. doi:10.1007/s12542-023-00667-5.
  7. Bouchet, P.; Rocroi, J.-P.; Hausdorf, B.; Kaim, A.; Kano, Y.; Nützel, A.; Parkhaev, P.; Schrödl, M.; Strong, E.E. (2017). "Revised classification, nomenclator and typification of gastropod and monoplacophoran families". Malacologia. 61 (1–2): 1–526. doi:10.4002/040.061.0201.
  • S. N. Rozov. 1975. A new order of the Monoplacophora. Paleontological Journal 15(1):39-43
  • G.P. Wahlman. 1992. Middle and Upper Ordovician symmetrical univalved mollusks (Monoplacophora and Bellerophontina) of the Cincinnati Arch region. United States Geological Survey Professional Paper 1066(O):1-123


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