Kirengellida
| Kirengellida Temporal range: Late Cambrian–Mid Ordovician | |
|---|---|
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Brachiopoda (?) |
| Order: | †Kirengellida |
| Family: | †Kirengellidae |
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
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
- ↑ 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. p. 60.
- 1 2 3 4 5 Dzik, Jerzy (2010). "BRACHIOPOD IDENTITY OF THE ALLEGED MONOPLACOPHORAN ANCESTORS OF CEPHALOPODS" (PDF). Malacologia. 52 (1): 97–113.