Pleurotomarioidea
Encyclopedia
Pleurotomarioidea is a superfamily
of small to large marine
gastropods included in the Vetigastropoda
.
These are the slit shells, originally named Pleurotomariacea
, in keeping with the convention for naming superfamilies at the time.
, with only the Pleurotomariidae surviving the extinction – and then only in deep waters.
Living representatives of the group were first discovered in the mid-19th century, and their unusual mix of primitive and derived characters perplexed biologists. The researchers originally responded by re-working their ideas of how the gastropod lineage evolved, but with the introduction of cladistics
, attempts are currently underway to fit them into a molluscan phylogeny.
which is included in the Prosobranchia
.
:
(Families that are exclusively fossil are indicated with a dagger †)
Bouchet and Rocroi (2005) includes the Pleurotomarioidea in the Vetigastropoda, following Ponder and Lindberg (1997), but refers to the Vetigastropoda simply as a clade.
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
of small to large marine
Marine (ocean)
Marine is an umbrella term. As an adjective it is usually applicable to things relating to the sea or ocean, such as marine biology, marine ecology and marine geology...
gastropods included in the Vetigastropoda
Vetigastropoda
Vetigastropoda is a major taxonomic group of sea snails, marine gastropod mollusks that form a very ancient lineage. Taxonomically Vetigastropoda are sometimes treated as an order although they are a clade in Bouchet and Rocroi, 2005....
.
These are the slit shells, originally named Pleurotomariacea
Pleurotomariacea
The superfamily Pleurotomariacea, based on Swainson, 1840 and described in the Treatise on Invertebrate Paleontology, was established for mostly conispiral, but also discoidal and auriform shells that have a nacreous, aragonite, inner layer.The Pleurotomariacea, now often seen as...
, in keeping with the convention for naming superfamilies at the time.
Evolutionary history
Forming the first evidence of crown-group gastropods when they appeared in the Upper Cambrian, the fossil record of the Pleurotomarioideans has no substantial gaps until today. The group took quite a hit at the K–T boundaryK–T boundary
The K–T boundary is a geological signature, usually a thin band, dated to 65.5 ± 0.3 Ma ago. K is the traditional abbreviation for the Cretaceous period, and T is the abbreviation for the Tertiary period...
, with only the Pleurotomariidae surviving the extinction – and then only in deep waters.
Living representatives of the group were first discovered in the mid-19th century, and their unusual mix of primitive and derived characters perplexed biologists. The researchers originally responded by re-working their ideas of how the gastropod lineage evolved, but with the introduction of cladistics
Cladistics
Cladistics is a method of classifying species of organisms into groups called clades, which consist of an ancestor organism and all its descendants . For example, birds, dinosaurs, crocodiles, and all descendants of their most recent common ancestor form a clade...
, attempts are currently underway to fit them into a molluscan phylogeny.
2004 taxonomy
J. D. Stilwell et al. 2004 put the Pleurotomarioidea in the order ArchaeogastropodaArchaeogastropoda
Archaeogastropoda was a taxonomic order of sea snails used in older classifications of gastropods, i.e. snails and slugs. Archeogastropoda are marine prosobranch gastropod mollusks, mainly herbivores, typically having two gills and a double-chambered heart, with the eggs and sperm discharged...
which is included in the Prosobranchia
Prosobranchia
Not to be confused with the bivalve order Protobranchia.Prosobranchia was a large taxonomic subclass of sea snails, land snails and freshwater snails. This taxon of gastropods dates back to the 1920s...
.
1993 and 2005 taxonomy
The following families have been recognized in taxonomy by Tracey at al. (1993) and in the taxonomy of Bouchet & Rocroi (2005)Taxonomy of the Gastropoda (Bouchet & Rocroi, 2005)
The taxonomy of the Gastropoda as it was revised by Philippe Bouchet and Jean-Pierre Rocroi is currently the most up-to-date overall system for classifying gastropod mollusks...
:
(Families that are exclusively fossil are indicated with a dagger †)
- family PleurotomariidaePleurotomariidaePleurotomariidae, common name the '"slit snails", is a family of large marine gastropods in the clade Vetigastropoda. This family is very ancient; there were numerous species in the geological past. It is currently represented by a group of species that live only in deep water...
- † family CatantostomatidaeCatantostomatidaeCatantostomatidae is an extinct family of marine gastropods included in the Vetigastropoda and placed in the superfamily Pleurotomarioidea...
- † family KittlidiscidaeKittlidiscidaeKittlidiscidae is an extinct family of Middle Triassic gastropods in the superfamily Pleurotomarioidea, named to contain the genus Kittlidiscus and included in the Vetigastropoda....
- † family PhymatopleuridaePhymatopleuridaePhymatopleuridae is an extinct family of gastropods in the clade Vetigastropoda .This family has no subfamilies.- Genera :Genera within the family Phymatopleuridae include:...
- † family PolytremariidaePolytremariidaePolytremariidae is an extinct family of gastropods in the clade Vetigastropoda .This family has no subfamilies....
- † family PortlockiellidaePortlockiellidaePortlockiellidae is an extinct family of gastropods in the clade Vetigastropoda .This family has no subfamilies.- Genera :Genera within the family Portlockiellidae include:...
- † family RhaphischismatidaeRhaphischismatidaeRhaphischismatidae is an extinct family of gastropods from the Lower Carboniferous , containing a single genus, Raphischisma, and uncluded in the superorder Vetigastropoda...
- † family TrochotomidaeTrochotomidaeTrochotomidae is an extinct family of gastropods in the clade Vetigastropoda .This family has no subfamilies....
- † family ZygitidaeZygitidaeZygitidae is an extinct family of fossil sea snails, marine gastropod mollusks in the clade Vetigastropoda .This family has no subfamilies....
Bouchet and Rocroi (2005) includes the Pleurotomarioidea in the Vetigastropoda, following Ponder and Lindberg (1997), but refers to the Vetigastropoda simply as a clade.