Stenothecidae

Stenothecidae is an extinct family of fossil univalved Cambrian molluscs which may be either gastropods or monoplacophorans.

Stenothecidae Temporal range: Lower Cambrian – Mid Cambrian[1] PreꞒ Ꞓ O S D C P T J K Pg N
Scientific classification
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Gastropoda or Monoplacophora
Superfamily:	Yochelcionelloidea
Family:	Stenothecidae Runegar & Jell, 1980[2]
Genera
See text

The name of this taxon should not be confused with that of the class Stenothecoida, a group of problematic Cambrian invertebrates that have a bivalved (dorsal and ventral) shell.[1]

Morphology

The group comprises conical laterally compressed shells that may be smooth or ornamented with folds or ribs.[3] The shells are broadly limpet-like, which led to their initial consideration as monoplacophoran molluscs.[1]

Taxonomy

The taxonomic position of the group is unclear;[4] it has been classified as a Yochelcionelloid or Helcionelloid.[5] It is not obviously in the stem group of any modern molluscan class, and has been referred to the monoplacophora,[3] although the monoplacophora are no longer considered to be a clade, and thus that classification means little more than "primitive mollusc".[6]

Genera

The family Stenothecidae consists of two subfamilies and the following genera:

• Stenothecinae Runegar & Jell, 1980 - synonym: Mellopegmidae Missarzhevsky, 1989[7]
  • Stenotheca Salter [in Hicks], 1872 - type genus of the family Stenothecidae
  • Mellopegma Runegar & Jell, 1976
• Watsonellinae Parkhaev, 2001[5]
  • Watsonella Grabau, 1900[8] - type genus of the subfamily Watsonellinae
    • Watsonella crosbyi Grabau - type species of the genus Watsonella

References

1. Yochelson, E. L. (1969). "Stenothecoida, A Proposed New Class of Cambrian Mollusca". Lethaia. 2: 49–62. doi:10.1111/j.1502-3931.1969.tb01250.x.
2. Runegar & Jell. 1980. Alcheringa, 4(2): 111.
3. Runnegar, B.; Pojeta Jr, J. (Oct 1974). "Molluscan Phylogeny: the Paleontological Viewpoint". Science. 186 (4161): 311–317. Bibcode:1974Sci...186..311R. doi:10.1126/science.186.4161.311. JSTOR 1739764. PMID 17839855.
4. Bouchet, Philippe; Rocroi, Jean-Pierre; Frýda, Jiri; Hausdorf, Bernard; Ponder, Winston; Valdés, Ángel & Warén, Anders (2005). "Classification and nomenclator of gastropod families". Malacologia. Hackenheim, Germany: ConchBooks. 47 (1–2): 1–397. ISBN 3-925919-72-4. ISSN 0076-2997.
5. Parkhaev P. Yu. 2001. Molluscs and siphonoconchs. In: Alexander E. M. et al. (eds.) The Cambrian biostratigraphy of the Stansbury basin, South Australia. Transactions of the Paleontological Institute, Russian Academy of Sciences, 282: 133-210, plates 24-54. Watsonellinae on the page 187.
6. Budd, G. E.; Jensen, S. (2000). "A critical reappraisal of the fossil record of the bilaterian phyla". Biological Reviews of the Cambridge Philosophical Society. 75 (2): 253–95. doi:10.1111/j.1469-185X.1999.tb00046.x. PMID 10881389.
7. (in Russian) Missarzhevsky. (after 10 July) 1989. Drevneishie skeletnye okamenelosti i stratigrafiia pogranichnykh tolshch Dokembriia i Kembiia. (English translation: Oldest skeletal fossils and stratigraphy of Precambrian and Cambrian boundary beds.) Trudy Geologicheskogo Instituta, Akademia Nauk SSSR, 443, 237 pp., 32 plates. Mellopegmidae is on the page 179.
8. Grabau A. W. 1900. Palaeontology of the Cambrian terranes of the Boston Basin. Occasional Papers of the Boston Society of Natural History 4:601-694.

Further reading

• Kouchinsky, A. V. (1999). "Shell microstructures of the Early Cambrian Anabarella and Watsonella as new evidence on the origin of the Rostroconchia". Lethaia. 32 (2): 173–180. doi:10.1111/j.1502-3931.1999.tb00537.x.
• http://www.palaeos.org/Stenothecoida