Stenothecidae is an extinct

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...

univalved Cambrian

mollusc Mollusca is a phylum of protostome, protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant taxon, extant species of molluscs are recognized, making it the second-largest animal phylum ...

s which may be either

gastropod Gastropods (), commonly known as slugs and snails, belong to a large Taxonomy (biology), taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, freshwater, and fro ...

s or

monoplacophora Shell of Monoplacophora Monoplacophora , meaning "bearing one plate", is a polyphyletic class of molluscs with a cap-like shell, inhabiting deep sea environments. Extant representatives were not recognized as such until 1952; previously they wer ...

ns. 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.

Morphology

The group comprises conical laterally compressed shells that may be smooth or ornamented with folds or ribs. The shells are broadly

limpet Limpets are a group of aquatic snails with a conical gastropod shell, shell shape (patelliform) and a strong, muscular foot. This general category of conical shell is known as "patelliform" (dish-shaped). Existing within the class Gastropoda, ...

-like, which led to their initial consideration as monoplacophoran molluscs.

Taxonomy

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

Genera

The family Stenothecidae consists of two subfamilies and the following genera: * Stenothecinae Runegar & Jell, 1980 - synonym: Mellopegmidae Missarzhevsky, 1989 ** '' Stenotheca'' Salter n Hicks 1872 –

type genus In biological taxonomy, the type genus (''genus typica'') is the genus which defines a biological family and the root of the family name. Zoological nomenclature According to the International Code of Zoological Nomenclature, "The name-bearin ...

of the family Stenothecidae ** '' Mellopegma'' Runegar & Jell, 1976 * Watsonellinae Parkhaev, 2001Parkhaev 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. ** '' Watsonella''

Grabau Grabau is a surname. Notable people with the surname include: * Aaron Grabau (born 1978), Australian basketball player * Amadeus William Grabau (1870–1946), geologist * Charles Grabau, jurist * Johannes Andreas August Grabau (1804–1879), t ...

, 1900 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. – type genus of the subfamily Watsonellinae *** '' Watsonella crosbyi'' Grabau – type species of the genus ''Watsonella''

Morphology

Taxonomy

Genera

References

Further reading