''Strepsodiscus'' is an extinct
genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...
of very primitive
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 preserved ...
snail
A snail is, in loose terms, a shelled gastropod. The name is most often applied to land snails, terrestrial pulmonate gastropod molluscs. However, the common name ''snail'' is also used for most of the members of the molluscan class G ...
-like
molluscs from the early part of the Late
Cambrian (
Dresbachian
The Dresbachian is a Maentwrogian regional stage of North America, lasting from 501 to 497 million years ago. It is part of the Upper Cambrian and is defined by four trilobite zones. It overlaps with the International Commission on Stratigraphy, IC ...
Age) of
North America. The coiled, slightly asymmetrical shells are about 3 cm in height. It is not known whether these are shells of
gastropods (
sea snails) or
monoplacophora
Monoplacophora , meaning "bearing one plate", is a polyphyletic superclass of molluscs with a cap-like shell inhabiting deep sea environments . Extant representatives were not recognized as such until 1952; previously they were known only from ...
ns, which are more primitive mollusks.
Bouchet & Rocroi (2005)
[Bouchet P. & Rocroi J.-P. (Ed.); Frýda J., Hausdorf B., Ponder W., Valdes A. & Warén A. 2005. ''Classification and nomenclator of gastropod families''. Malacologia: International Journal of Malacology, 47(1-2). ConchBooks: Hackenheim, Germany. . ISSN 0076-2997. 397 pp. http://www.vliz.be/Vmdcdata/imis2/ref.php?refid=78278] divide the Bellerophontoidea into 8 families listed
Paleozoic molluscs with isostrophically coiled shells of uncertain position within Mollusca (Gastropoda or Monoplacophora)
Knight, et al., 1960 included this genus within the
Cyrtolitidae, a
paraphyletic or
polyphyletic
A polyphyletic group is an assemblage of organisms or other evolving elements that is of mixed evolutionary origin. The term is often applied to groups that share similar features known as homoplasies, which are explained as a result of conver ...
assemblage of proto-gastropods and
Tergomyan molluscs. ''Strepsodiscus'' may be too primitive to be a true
gastropod.
Species
Species within the genus ''Strepsodiscus'' are as follows
* ''Strepsodiscus major''
* ''S. minutissimus''
* ''S. paucivoluta''
* ''S. splettstoesseri''
* ''S. strongi''
References
* Knight, J. B., Cox, L. R., Keen, A. M., Batten, R. L., Yochelson, E. L., and Robertson, R. (1960). Systematic descriptions (Archaeogastropoda). In Moore, R. C. (ed.)
Treatise on Invertebrate Paleontology
The ''Treatise on Invertebrate Paleontology'' (or ''TIP'') published by the Geological Society of America and the University of Kansas Press, is a definitive multi-authored work of some 50 volumes, written by more than 300 paleontologists, and co ...
. Part I. Mollusca 1, pp. 169–310. Geological Society of America and Kansas University Press, Colorado and Kansas.
*
Wagner, P. J. (1999). Phylogenetics of the earliest anisostrophically coiled gastropods. ''Smithsonian Contributions to Paleobiology'' 88: 1 - 132.
External links
Strepsodiscus- Palaeos
* A possible reference
* Info at Paleobiology Database
Cambrian molluscs
Cambrian animals of North America
Paleozoic life of Quebec
{{paleo-mollusc-stub
Cambrian genus extinctions