Pleurotomarioidea is a

superfamily SUPERFAMILY is a database and search platform of structural and functional annotation for all proteins and genomes. It classifies amino acid sequences into known structural domains, especially into SCOP superfamilies. Domains are functional, str ...

of small to large

marine Marine is an adjective meaning of or pertaining to the sea or ocean. Marine or marines may refer to: Ocean * Maritime (disambiguation) * Marine art * Marine biology * Marine debris * Marine habitats * Marine life * Marine pollution Military * ...

gastropod The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, from freshwater, and from land. T ...

s included in the order Pleurotomariida of the subclass

Vetigastropoda Vetigastropoda is a major Taxonomy (biology), taxonomic group of sea snails, marine (ocean), marine gastropod mollusc, mollusks that form a very ancient lineage (evolution), lineage. Taxonomically the Vetigastropoda are sometimes treated as an O ...

. These are the slit shells, originally named

Pleurotomariacea Pleurotomariacea is one of two names that are used for a taxonomic superfamily of sea snails that are an ancient lineage and are well represented in the fossil record. The name Pleurotomariacea is used by paleontologists, who, because they us ...

, in keeping with the convention for naming superfamilies at the time. This updated version of the name for the taxon is usually used by students of the living Mollusca.

Paleontologist Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (roughly 11,700 years before present). It includes the study of fossi ...

s often still use the name

instead.

Evolutionary history

Forming the first evidence of crown-group gastropods when they appeared in the

Upper Cambrian The Furongian is the fourth and final epoch and series of the Cambrian. It lasted from to million years ago. It succeeds the Miaolingian series of the Cambrian and precedes the Lower Ordovician Tremadocian Stage. It is subdivided into three ...

, the fossil record of the Pleurotomarioideans has no substantial gaps until today. The group took quite a hit at the

Cretaceous–Paleogene boundary The Cretaceous–Paleogene (K–Pg) boundary, formerly known as the Cretaceous–Tertiary (K–T) boundary, is a geological signature, usually a thin band of rock containing much more iridium than other bands. The K–Pg boundary marks the end of ...

(K–T boundary), with only the Pleurotomariidae surviving the

Cretaceous–Paleogene extinction event The Cretaceous–Paleogene (K–Pg) extinction event (also known as the Cretaceous–Tertiary extinction) was a sudden mass extinction of three-quarters of the plant and animal species on Earth, approximately 66 million years ago. With the ...

– 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 (; ) is an approach to biological classification in which organisms are categorized in groups (" clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is typically shared derived char ...

, attempts are currently underway to fit them into a molluscan phylogeny.

Taxonomy

2004 taxonomy

J. D. Stilwell et al. 2004 Classification of J. D. Stilwell et al. 2004
J. D. Stilwell, W. J. Zinsmeister, and A. E. Oleinik. 2004. Early Paleocene Mollusks of Antarctica: Systematics, Paleoecology and Paleobiogeographic Significance. Bulletins of American Paleontology 367 put the Pleurotomarioidea in the order

Archaeogastropoda Archaeogastropoda (also known as Aspidobranchia) 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 havi ...

which is included in the

Prosobranchia Prosobranchia was a large taxonomic subclass of sea snails, land snails and freshwater snails. This taxon of gastropods dates back to the 1920s. It has however been proven to be polyphyletic (consisting of more than one lineage of descent). Gene ...

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): * family Pleurotomariidae * † family Catantostomatidae * † family Kittlidiscidae * † family Phymatopleuridae * † family Polytremariidae * † family Portlockiellidae * † family Rhaphischismatidae * † family Trochotomidae * † family Zygitidae Bouchet and Rocroi (2005) includes the Pleurotomarioidea in the Vetigastropoda, following Ponder and Lindberg (1997), but refers to the Vetigastropoda simply as a clade.

2008 taxonomy

P. J. Wagner 2008Classification of P. J. Wagner 2008
P. J. Wagner. 2008. Paleozoic Gastropod, Rostroconch, Helcionelloid and Tergomyan Database. http://paleodb.org/cgi-bin/bridge.pl?action=displayReference&reference_no=9042 (unpublished). includes the superfamily Pleurotomarioidea, (ex Pleurotomariacea) in the suborder Pleurotomariina and superorder Vetigastropoda. This is an as yet (September 2010) unpublished opinion by Wagner.

References

{{Taxonbar, from=Q2461972 Vetigastropoda