Neogastropoda

Neogastropoda is a clade of sea snails, both freshwater and marine gastropod mollusks.[1][2]

Neogastropoda
Temporal range: Early Cretaceous–Recent
Chicoreus palmarosae
The shell of a neogastropod, the muricid species Chicoreus palmarosae
Scientific classification
Kingdom: Animalia
Phylum: Mollusca
Class: Gastropoda
Clade: Caenogastropoda
Clade: Hypsogastropoda
Clade: Neogastropoda
Wenz, 1938
Superfamilies

See text

Description

The available fossil record of Neogastropoda is relatively complete, and supports a widely accepted evolutionary scenario of an Early Cretaceous origin of the group followed by two rapid diversification rounds in the late Cretaceous and the Paleocene.[3]

These sea snails only have one auricle, one kidney and one monopectinate gill, i.e. the gill filaments develop on only one side of the central axis.[4]

The shell has a well-developed siphonal canal. The elongated trunk-like siphon is an extensible tube, formed from a fold in the mantle. It is used to suck water into the mantle cavity. At the base of the siphon is the bipectinate (branching from a central axis) osphradium, a sensory receptacle and olfactory organ, that is more developed than the one in the Mesogastropoda. They achieved important morphological changes including e.g., the elongation of the siphonal canal, a shift in the mouth opening to a terminal position on the head, and the formation of a well-developed proboscis.[3]

The nervous system is very concentrated. Many species have the ganglia in a compact space.

The rachiglossate (rasp-like) radula, a layer of serially arranged teeth within the mouth, has only three denticles (small teeth) in each transverse row.[4]

The Neogastropoda have separate sexes.

There are about 16,000 species. Neogastropoda includes many well-known gastropods including the cone snails, conchs, mud snails, olive snails, oyster drills, tulip shells, and whelks. The Neogastropoda all live in the sea, except Clea, and Rivomarginella that are freshwater genera. The neogastropods are most diverse in tropical seas.[3] They are mostly predators, but some are saprophagous (scavengers).

Taxonomy

According to the taxonomy of the Gastropoda by Bouchet & Rocroi (2005) the clade Neogastropoda consists of these superfamilies:

When Neogastropoda was an order, it was placed within the prosobranch gastropods according to the taxonomy developed by Thiele (1921). The families which used to form the order Neogastropoda are now included in the clade Neogastropoda Cox, 1960.

Ever since Thiele (1929),[6] Neogastropoda have been considered a natural group, clearly differentiated from other Caenogastropoda.[3] The monophyly of the group is widely accepted among morphologists, and it is based on several synapomorphies mostly related with the anatomy of the digestive system.[3] Current classifications of Neogastropoda generally recognize up to six superfamilies: Buccinoidea, Muricoidea, Olivoidea, Pseudolivoidea, Conoidea, and Cancellarioidea. Phylogenetic relationships among neogastropod superfamilies based on morphological characters are rather unstable, and for instance, Cancellarioidea[7] or Buccinoidea[8] have been alternatively proposed as the sister group of the remaining Neogastropoda.[3]

Families

According to the taxonomy of the Gastropoda by Bouchet & Rocroi (2005) the taxonomy of clade Neogastropoda is as follows:

References

This article incorporates CC BY 2.0 text from the reference.[3]

  1. ^ "WoRMS - World Register of Marine Species - Neogastropoda". www.marinespecies.org. Retrieved 27 September 2018.
  2. ^ "ITIS Standard Report Page: Neogastropoda". www.itis.gov. Retrieved 27 September 2018.
  3. ^ a b c d e f g Cunha R. L., Grande C. & Zardoya R. (23 August 2009). "Neogastropod phylogenetic relationships based on entire mitochondrial genomes". BMC Evolutionary Biology 2009, 9: 210. 10.1186/1471-2148-9-210
  4. ^ a b Barnes, Robert D. (1982). Invertebrate Zoology. Philadelphia, PA: Holt-Saunders International. p. 376. ISBN 978-0-03-056747-6.
  5. ^ Bouchet P., Rocroi J.P., Hausdorf B., Kaim A., Kano Y., Nützel A., Parkhaev P., Schrödl M. & Strong E.E. (2017). Revised classification, nomenclator and typification of gastropod and monoplacophoran families. Malacologia. 61(1-2): 1-526
  6. ^ Thiele J. (1929). Handbuch der Systematischen Weichtierkunde Volume 1 (1) (Loricata; Gastropoda: Prosobranchia). Jena, 376 pp. In: (23 October 1929). Reprint, Asher & Co., Amsterdam, 1963; translation by J.S. Bhatti Edited by: R. Bieler & P. Mikkelsen, Smithsonian Libraries, 1993.
  7. ^ Kantor YI. (1996). Phylogeny and Relationships of Neogastropoda. In: Taylor J. D. (ed.) Origin and Evolutionary Radiation of the Mollusca. Oxford, Oxford University Press, 221-230.
  8. ^ Ponder W. F., Colgan D. J., Healy J. M., Nützel A., Simone L. R. L. & Strong E. (2008). Caenogastropoda. In: Ponder W. F., Lindberg D. R. Phylogeny and evolution of the Mollusca. Berkeley, University of California Press, 331-383.

External links

Buccinoidea

Buccinoidea is a taxonomic superfamily of very small to large predatory sea snails, marine gastropod mollusks.

This superfamily is in the clade Neogastropoda according to the taxonomy of the Gastropoda (Bouchet & Rocroi, 2005). It had been placed within the infraorder Neogastropoda according to the taxonomy of the Gastropoda (Ponder & Lindberg, 1997).

Cancellariidae

Cancellariidae, common name the nutmeg snails or nutmeg shells, are a family of small to medium-large sea snails, marine gastropod mollusks in the clade Neogastropoda. Some of the shells of the species in this family resemble a nutmeg seed.

Cancellariidae is the only family in the superfamily Cancellarioidea.

Columbellidae

The Columbellidae, the dove snails or dove shells, are a family of minute to small sea snails, marine gastropod mollusks in the order Neogastropoda.

Conoidea

Conoidea is a superfamily of predatory sea snails, marine gastropod mollusks within the suborder Hypsogastropoda. This superfamily is a very large group of marine mollusks, estimated at about 340 recent valid genera and subgenera, and considered by one authority to contain 4,000 named living species.This superfamily includes the turrids, the terebras (also known as auger snails or auger shells) and the cones or cone snails. The phylogenetic relationships within this superfamily are poorly established. Several families (especially the Turridae), subfamilies and genera are thought to be polyphyletic.In contrast to Puillandre's estimate, Bandyopadhyay et al. (2008) estimated that the superfamily Conoidea contains about 10,000 species. Tucker (2004) even speaks of 11,350 species in the group of taxa commonly referred to as turrids. 3000 recent taxa are potentially valid species. Little more than half of the known taxa are fossil species. Many species are little known and need more investigation to find their exact systematic place.Most species in this superfamily are small to medium, with shell lengths between 3 mm and 50 mm. They occur in diverse marine habitats from tropical waters to the poles, in shallow or deep waters, and on hard to soft substrates.

The superfamily is known for its toxoglossan radula, which is used to inject powerful neurotoxins into its prey. This makes these species powerful carnivorous predators on annelid, other mollusc and even fish.

Within the superfamily there are four somewhat different varieties of radula. The radula types are as follows:

Type 1 Drilliidae type: five teeth in each row with comb-like lateral teeth and flat-pointed marginal teeth

Type 2 Turridae s.l. type: two or three teeth in a row with the marginal teeth being of the duplex or wishbone form.

Type 3 Pseudomelatomidae type: two or three teeth in a row with curved and solid marginal teeth.

Type 4 hypodermic type: two hollow, enrolled, marginal teeth in each row with an absent or reduced radular membrane.In 2009, a proposed new classification of this superfamily was published by John K. Tucker and Manuel J. Tenorio. In 2011, a new classification of this superfamily was published by Bouchet et al. Both classifications were based upon cladistical analyses and included modern taxonomic molecular phylogeny studies.

Hypsogastropoda

Hypsogastropoda is a clade containing marine gastropods within the clade Caenogastropoda.This clade contains two clades and one informal group:

Clade Littorinimorpha

Informal group Ptenoglossa

Clade Neogastropoda

Littorinimorpha

Littorinimorpha is a large clade of snails, gastropods, consisting primarily of sea snails (marine species), but also including some freshwater snails (aquatic species) and land snails (terrestrial species).Previously, the Linnaean taxonomy used in the taxonomy of the Gastropoda by Ponder & Lindberg (1997) ranked like this: subclass Orthogastropoda, superorder Caenogastropoda, order Sorbeoconcha, suborder Hypsogastropoda, infraorder Littorinimorpha.

The order Littorinimorpha contains many gastropoda families that were formerly placed in the order Mesogastropoda, as introduced by J. Thiele in his work from 1921. Evidence for this group being monophyletic is scanty. In 2003, E. E. Strong suggested using only Neogastropoda as a clade within the clade Hypsogastropoda, and to include the unresolved superfamilies of the Hypsogastropoda within the Littorinimorpha.

Mitroidea

Mitroidea is a superfamily of Recent and fossil sea snails, marine gastropod mollusks within the order Neogastropoda.

Muricidae

Muricidae is a large and varied taxonomic family of small to large predatory sea snails, marine gastropod mollusks, commonly known as murex snails or rock snails. With about 1,600 living species, the Muricidae represent almost 10% of the Neogastropoda. Additionally, 1,200 fossil species have been recognized. Numerous subfamilies are recognized, although experts disagree about the subfamily divisions and the definitions of the genera.

Many muricids have unusual shells which are considered attractive by shell collectors and by interior designers.

Muricoidea

Muricoidea is a taxonomic superfamily of predatory sea snails, marine gastropod mollusks in the clade Neogastropoda.This superfamily includes the murex snails, the chank snails, the dove snails, the volutes, the harp snails, the margin snails, the miters, and others.

Olive snail

Olive snails, also known as olive shells and olives, scientific name Olividae, are a taxonomic family of medium to large predatory sea snails with smooth, shiny, elongated oval-shaped shells.The shells often show various muted but attractive colors, and may be patterned also. They are marine gastropod molluscs in the family Olividae within the main clade Neogastropoda.

Also see the Olivellidae, the dwarf olives, which were previously grouped within this family, but which now have their own family.

Olivellidae

Olivellidae, common name the "dwarf olives", are a family of small predatory sea snails with smooth, shiny, elongated oval-shaped shells. The shells sometimes show muted but attractive colors, and may have some patterning.

These animals are marine gastropod molluscs in the superfamily Olivoidea, within the clade Neogastropoda according to the taxonomy of Bouchet and Rocroi.

Olivoidea

Olivoidea is a taxonomic superfamily of minute to medium-large predatory sea snails, marine gastropod mollusks in the clade Neogastropoda.

Persiculinae

Persiculinae is a taxonomic subfamily of minute to small predatory sea snails, marine gastropod mollusks. This subfamily includes several species which are micromollusks.

The subfamily is sometimes placed in the family Cystiscidae, and is sometimes instead left in the family Marginellidae the margin snails. It is within the clade Neogastropoda.

(Note: Gastropod taxonomy has been in flux for more than half a century, and this is especially true currently, because of new research in molecular phylogeny. Because of all the ongoing changes, different reliable sources can yield very different classifications.)

Pseudolivoidea

Pseudolivoidea is a taxonomic superfamily of sea snails, marine gastropod mollusks in the clade Neogastropoda.

Pseudomelatomidae

Pseudomelatomidae is a family of predatory sea snails, marine gastropods included in the superfamily Conoidea (previously Conacea) and part of the Neogastropoda (Bouchet & Rocroi, 2005).In 1995 Kantor elevated the subfamily Pseudomelatominae to the status of family Pseudomelatomidae. In 2011 Bouchet, Kantor et al. moved the Crassispirinae and Zonulispirinae and numerous genera of snails loosely called turrid snails (which at that point had been placed in the family Conidae) and placed them in the family Pseudomelatomidae. This was based on a cladistical analysis of shell morphology, radular characteristics, anatomical characters, and a dataset of molecular sequences of three gene fragments.

Siphonal canal

The siphonal canal is an anatomical feature of the shells of certain groups of sea snails within the clade Neogastropoda. Some sea marine gastropods have a soft tubular anterior extension of the mantle called a siphon through which water is drawn into the mantle cavity and over the gill and which serves as a chemoreceptor to locate food. In certain groups of carnivorous snails, where the siphon is particularly long, the structure of the shell has been modified in order to house and protect the soft structure of the siphon. Thus the siphonal canal is a semi-tubular extension of the aperture of the shell through which the siphon is extended when the animal is active.

One gastropod whose shell has an exceptionally long siphonal canal is the Venus comb murex. Some gastropods have a simple siphonal notch at the edge of the aperture instead of a canal.

Turbinellidae

Turbinellidae are a family of sea snails, marine gastropod mollusks in the clade Neogastropoda.

Turbinelloidea

Turbinelloidea is a superfamily of sea snails in the order Neogastropoda. It comprises the following families:

Columbariidae Tomlin, 1928

Costellariidae MacDonald, 1860

Ptychatractidae Stimpson, 1865

Turbinellidae Swainson, 1835

Volutomitridae Gray, 1854Families brought into synonymy

Cynodontidae MacDonald, 1860: synonym of Vasinae H. Adams & A. Adams, 1853 (1840)

Vasidae H. Adams & A. Adams, 1853: synonym of Turbinellidae Swainson, 1835

Vexillidae Thiele, 1929: synonym of Costellariidae MacDonald, 1860

Xancidae Pilsbry, 1922: synonym of Turbinellidae Swainson, 1835

Varix (mollusc)

A varix (Pl. varices) is an anatomical feature of the shell of certain sea snails, marine gastropod molluscs. Gastropods whose shells have varices are primarily families and species within the taxonomic groups Littorinimorpha and Neogastropoda.

The varix is a thickened axial ridge, a subcylindrical protrusion, in the shell which exists in some families of marine gastropods. It is an important shell character in generic classification. A varix is located at intervals around the whorl, and is formed by considerable thickening of the outer lip during a resting stage in the growth of the shell. In other words, in gastropods whose shells have varices, the shells are characterised by episodic growth - the shell grows in spurts, and during the resting phase the varix forms.

In many gastropod whose shells have varices, for example the Cassinae, the varix is essentially merely a thickening and swelling of the shell at that point. But in some genera within the family Muricidae, such as Chicoreus, Hexaplex, Pteropurpura and Pterynotus, and also within the genus Biplex, of the family Ranellidae, the varices are characterised by elaborate ruffles, frills or lamellae. Some other genera, for example Murex, are armed with protective spines which may be straight or curved, and which are formed by the varices closing or curling around their axis.

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