Notaspidea, also known as the sidegill slugs, is an artificial grouping of

sea slugs Sea slug is a common name for some marine invertebrates with varying levels of resemblance to terrestrial slugs. Most creatures known as sea slugs are gastropods, i.e. they are sea snails (marine gastropod mollusks) that over evolutionary time ...

which is now split into two unrelated groups, the

Umbraculida Umbraculoidea is a superfamily of unusual false limpets with a thin soft patelliform shell, marine gastropod molluscs in the clade Umbraculida, within the clade Euopisthobranchia. There are two families in this superfamily, which is listed as ...

and the

Pleurobranchomorpha The Pleurobranchidae are a taxonomic family of sea slugs, marine gastropod molluscs in the clade Pleurobranchomorpha. Characteristics Species in the family Pleurobranchidae have a prominent mantle and an internal shell that becomes reduced ...

Taxonomic history

Notaspidea, also known as the sidegill slugs, was a suborder which included both

sea slug Sea slug is a common name for some marine invertebrates with varying levels of resemblance to terrestrial slugs. Most creatures known as sea slugs are gastropods, i.e. they are sea snails (marine gastropod mollusks) that over evolutionary time ...

s and sea snails or false limpets, marine opisthobranch gastropod molluscs in the subclass Orthogastropoda. However, in the newer taxonomy of Bouchet & Rocroi (2005), the families Umbraculidae and Tylodinidae belong to the superfamily Umbraculoidea Dall, 1889, part of the clade Umbraculida. Grande ''et al.'' (2004) found Umbraculoidea to be a sister clade to the

Cephalaspidea The order Cephalaspidea, also known as the headshield slugs and bubble snails, is a major taxon of sea slugs and bubble snails, marine gastropod mollusks within the larger clade Euopisthobranchia.Jörger K. M., Stöger I., Kano Y., Fukuda H., ...

(Acteonoidea excluded). The families Tylodinidae and Umbraculidae have large limpet-like external shells and a small mantle, while the species in the family Pleurobranchidae have a prominent mantle and an internal shell that becomes reduced or is lost in adults. Many species produce mantle secretions as a chemical defense against predators

Families

* Pleurobranchidae Menke, 1828 * Tylodinidae Gray, 1847 * Umbraculidae Dall, 1889

Notes

References

* * Powell A. W. B., ''New Zealand Mollusca'', William Collins Publishers Ltd, Auckland, New Zealand 1979 {{Taxonbar, from=Q141484 Obsolete gastropod taxa