Euopisthobranchia
Encyclopedia
Euopisthobranchia is a taxonomic clade
of snails and slugs in the clade Heterobranchia
within the clade Euthyneura
.
Euopisthobranchia was established as a new taxon by Jörger et al. in October 2010.
Euopisthobranchia is a monophyletic portion of the "Opisthobranchia
" as that taxon was traditionally defined.
Euopisthobranchia consist of the following taxa:
of the larger clade of Paratectibranchia (Pteropoda, Cephalaspidea and Anaspidea) and Eleutherobranchia, secondarily lost in Nudipleura but still present in Umbraculoidea. As coded in Wägele and Klussmann-Kolb, phylogenetic hypothesis by Jörger et al. (2010) supports homology of the gizzard in Umbraculoidea with the gizzard with gizzard plates and spines in the other euopisthobranchian taxa. Thus, the structure is proposed as a synapomorphy of Euopisthobranchia.
showing phylogenic relations of the Heterobranchia as proposed by Jörger et al. (2010):
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
of snails and slugs in the clade Heterobranchia
Heterobranchia
Heterobranchia, the heterobranchs or Euthyneura, is a taxonomic clade of snails and slugs, which includes species from the sea, the land and freshwater; marine, aquatic and terrestrial gastropod mollusks....
within the clade Euthyneura
Euthyneura
Euthyneura is a taxonomic clade of snails and slugs, which includes species from the sea, the land and freshwater; marine, aquatic and terrestrial gastropod mollusks in the clade Heterobranchia....
.
Euopisthobranchia was established as a new taxon by Jörger et al. in October 2010.
Euopisthobranchia is a monophyletic portion of the "Opisthobranchia
Opisthobranchia
Opisthobranchs are a large and diverse group of specialized complex marine gastropods previously united under Opisthobranchia within the Heterobranchia, but no longer considered to represent a monophyletic grouping...
" as that taxon was traditionally defined.
Euopisthobranchia consist of the following taxa:
- UmbraculoideaUmbraculoideaThe superfamily Umbraculoidea are marine gastropod molluscs.These are two families of unusual false limpets, with a thin soft patelliform shell.-Taxonomy:...
- Anaspidea
- Runcinacea
- PteropodaPteropodaPteropoda, common name the pteropods, from the Greek meaning "wing-foot" is a term applied to what are now considered to be two separate taxonomic groups of specialized free-swimming pelagic sea snails and sea slugs, marine opisthobranch gastropods...
- CephalaspideaCephalaspideaThe suborder Cephalaspidea, also known as the headshield slugs and bubble snails, is a clade of sea slugs and bubble snails, marine gastropod mollusks within the larger clade Euopisthobranchia....
s.s.
Gizzard
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. 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. 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. This contradicted Salvini-Plawen and Steiner, who had proposed the gizzard to be a synapomorphySynapomorphy
In cladistics, a synapomorphy or synapomorphic character is a trait that is shared by two or more taxa and their most recent common ancestor, whose ancestor in turn does not possess the trait. A synapomorphy is thus an apomorphy visible in multiple taxa, where the trait in question originates in...
of the larger clade of Paratectibranchia (Pteropoda, Cephalaspidea and Anaspidea) and Eleutherobranchia, secondarily lost in Nudipleura but still present in Umbraculoidea. As coded in Wägele and Klussmann-Kolb, phylogenetic hypothesis by Jörger et al. (2010) supports homology of the gizzard in Umbraculoidea with the gizzard with gizzard plates and spines in the other euopisthobranchian taxa. Thus, the structure is proposed as a synapomorphy of Euopisthobranchia.
Cladogram
A cladogramCladogram
A cladogram is a diagram used in cladistics which shows ancestral relations between organisms, to represent the evolutionary tree of life. Although traditionally such cladograms were generated largely on the basis of morphological characters, DNA and RNA sequencing data and computational...
showing phylogenic relations of the Heterobranchia as proposed by Jörger et al. (2010):
See also
- Changes in the taxonomy of gastropods since 2005#Heterobranchia
- Heterobranchia#2010 taxonomy
- Acochlidiacea#2010 taxonomy