Stenothecoida

Not to be confused with Stenothecidae.
Stenothecoida
Temporal range: Early–mid-Cambrian, 525–500 Ma[1][2]
Scientific classification
Kingdom: Animalia
Phylum: Mollusca (?)
Class: †Stenothecoida
Yochelson, 1968

Stenothecoida are bivalved fossils from the Early Cambrian period.

Affinity

Their affinity is uncertain. They were considered by E. L. Yochelson 1968 to belong to Mollusca, whereas Runnegar and Pojeta (1974) suggested that they might be 'bivalved monoplacophorans'. This said, the morphology of the shell does not resemble the shell of any other class of molluscs; they also look a little like brachiopods[1] It's not clear whether their two valves are each others' mirror images, as in bivalve molluscs, though they aren't identical to one another [?].[1] It's more likely that the valves each have a single plane of symmetry (as in brachiopods), suggesting a brachiopod affiliation.[1]

As with many other Cambrian taxa,[3][4] it has been suggested that they arise through reduction of a Halkieria-like ancestor.[1]

Occurrence

The earliest occurrence dates to 525 Ma.[2]

These fossil shells have been found in Canada, China, Greenland, Kazakhstan, Kyrgyzstan, and the USA.

References

  1. 1 2 3 4 5 (PDF) https://www.researchgate.net/profile/Artem_Kouchinsky/publication/264808572_Molluscs_hyoliths_stenothecoids_and_coeloscleritiphorans/links/53f1ee860cf2bc0c40e6eed7.pdf. Missing or empty |title= (help)
  2. 1 2 Kouchinsky, A. V., Bengtson, S., Runnegar, B.N., Skovsted, C.B., Steiner, M., and Vendrasco, M.J. (2012). Chronology of early Cambrian biomineralization. Geol. Mag. 149, 221–251.
  3. ↑ 1. Cohen, B.L., Holmer, L.E., and Lüter, C. (2003). The brachiopod fold: a neglected body plan hypothesis. Palaeontology 46, 59–65.
  4. ↑ 1. Skovsted, C.B., Betts, M.J., Topper, T.P., and Brock, G.A. (2015). The early Cambrian tommotiid genus ~Dailyatia~ from South Australia. Mem. Assoc. Australas. Palaeontol. 48, 1–117.


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