Summary
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:
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|---|---|
Scientific classification 
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| 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 edit
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 edit
- ^ 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
- ^ Yochelson, E.L. (1978). "An alternative approach to the interpretation of the phylogeny of ancient mollusks". Malacologia. 17 (2): 165–191.
- ^ 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.
- ^ a b c d e Dzik, Jerzy (2010). "BRACHIOPOD IDENTITY OF THE ALLEGED MONOPLACOPHORAN ANCESTORS OF CEPHALOPODS" (PDF). Malacologia. 52 (1): 97–113.
- ^ 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.
- ^ 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.
- ^ 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