Kirengellidae

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Kirengellidae
Temporal range: Late Cambrian–Mid Ordovician
Scientific classification
Kingdom: Animalia
Phylum: Mollusca or Brachiopoda?

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.

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]

Included taxa[edit]

After [4]:fig. 5

  • Kirengella Rozov, 1968 (Upper Cambrian)
    • Kirengella ayaktchica - type species
    • Kirengella expansus]
    • Kirengella oregonensis
    • Kirengella pyramidalis
    • 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[edit]

  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  edit
  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". Minnesota Geological Survey Report of Investigations 64. p. 60. 
  4. ^ a b c d e Dzik, Jerzy (2010). "BRACHIOPOD IDENTITY OF THE ALLEGED MONOPLACOPHORAN ANCESTORS OF CEPHALOPODS". Malacologia 52 (1): 97-113.