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Pleurobranchaea meckelii.jpg
A live individual of Pleurobranchaea meckelii; the gill (or ctenidium) is visible in this view of the right-hand side of the animal
Scientific classification
Kingdom: Animalia
Phylum: Mollusca
Class: Gastropoda
Subclass: Orthogastropoda (older classification)
Superorder: Heterobranchia (new classification)
Order: Opisthobranchia (older classification)
Suborder: Notaspidea
P. Fischer, 1883

Notaspidea, also known as the sidegill slugs, is an artificial grouping of sea slugs which is now split into two unrelated groups, the Umbraculida and the Pleurobranchomorpha.[1]

Taxonomic history[edit]

Notaspidea, also known as the sidegill slugs, was a suborder which included both sea slugs 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 (Acteonoidea excluded).[2]

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.[3] Many species produce mantle secretions as a chemical defense against predators [4]



  1. ^ Gofas, S. (2014). Notaspidea. Accessed through: World Register of Marine Species at on 2015-02-12
  2. ^ Grande C.; J. Templado; J.L. Cervera; R. Zardoya (2004). "Phylogenetic relationships among Opisthobranchia (Mollusca, Gastropoda) based on mitochondrial cox1, tmV, and rmL genes". Molecular Phylogenetics and Evolution. 33 (2): 378–388. doi:10.1016/j.ympev.2004.06.008. PMID 15336672. 
  3. ^ R. Willan (1987). "Phylogenetic systematics of the Notaspidea (Opisthobranchia) with a reappraisal of families and genera". Am. Malacol. Bull. 5: 215–241. 
  4. ^ Aldo Spinella; Ernesto Mollo; Enrico Trivellone; Guido Cimino (December 1997). "Testudinariol A and B, two unusual triterpenoids from the skin and the mucus of the marine mollusc Pleurobrancus testudinarius.". Tetrahedron. 53 (49): 16891–16896. doi:10.1016/S0040-4020(97)10124-7.