Stenothecidae

Not to be confused with Stenothecoida.

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