Euopisthobranchia

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Euopisthobranchia
Scientific classification
Kingdom: Animalia
Phylum: Mollusca
Class: Gastropoda
(unranked): clade Heterobranchia

clade Euthyneura
clade Euopisthobranchia

Jörger et al., 2010[1]

Taxonomic subdivisions

See text

Euopisthobranchia is a taxonomic clade of snails and slugs in the clade Heterobranchia within the clade Euthyneura. This clade was established as a new taxon by Jörger et al. in October 2010.[1] Euopisthobranchia is a monophyletic portion of the Opisthobranchia as that taxon was traditionally defined but is not a replacement name for that group as several marine opisthobranch orders including Sacoglossa and Acochlidiacea are not included.[1]

Euopisthobranchia consist of the following taxa:[1]

Gizzard[edit]

Previous studies discussed the gizzard (i.e. a muscular oesophageal crop lined with cuticula) with gizzard plates as homologous apomorphic structures supporting a clade composed of Cephalaspidea s.s., Pteropoda and Anaspidea.[1] A gizzard with gizzard plates probably originated in herbivorous taxa in which it worked like a grinding mill, thus might be secondarily reduced in carnivorous groups within Cephalaspidea s.s. and Gymnosomata.[1] Klussmann-Kolb and Dinapoli considered the gizzard in Umbraculoidea as non-homologous with the one in the previous groups, on account of the absence of gizzard plates or spines.[1] This contradicted Salvini-Plawen and Steiner, who had proposed the gizzard to be a synapomorphy of the larger clade of Paratectibranchia (Pteropoda, Cephalaspidea and Anaspidea) and Eleutherobranchia, secondarily lost in Nudipleura but still present in Umbraculoidea.[1] As coded in Wägele and Klussmann-Kolb, phylogenetic hypothesis by Jörger et al. (2010)[1] supports homology of the gizzard in Umbraculoidea with the gizzard with gizzard plates and spines in the other euopisthobranchian taxa.[1] Thus, the structure is proposed as a synapomorphy of Euopisthobranchia.[1]

Cladogram[edit]

A cladogram showing phylogenic relations of the Heterobranchia as proposed by Jörger et al. (2010):[1]


Heterobranchia

Lower Heterobranchia (including Acteonoidea) - Lower Heterobranchia does not form a clade in the study by Jörger et al. (2010):[1]


Euthyneura
Nudipleura

Pleurobranchomorpha



Nudibranchia




Euopisthobranchia

Umbraculoidea





Runcinacea




Anaspidea



Pteropoda (pteropods include two clades: Gymnosomata and Thecosomata)





Cephalaspidea s.s.




Panpulmonata


Siphonarioidea



Sacoglossa






Glacidorboidea




Amphiboloidea



Pyramidelloidea






Hygrophila




Acochlidiacea


Eupulmonata

Stylommatophora




Systellommatophora




Ellobioidea




Otinoidea



Trimusculoidea














See also[edit]

References[edit]

This article incorporates CC-BY-2.0 text from the reference.[1]

  1. ^ a b c d e f g h i j k l m n Jörger K. M., Stöger I., Kano Y., Fukuda H., Knebelsberger T. & Schrödl M. (2010). "On the origin of Acochlidia and other enigmatic euthyneuran gastropods, with implications for the systematics of Heterobranchia". BMC Evolutionary Biology 10: 323. doi:10.1186/1471-2148-10-323.