Mesogastropoda
Encyclopedia
Mesogastropoda was for many years a traditional taxonomic group of snail
s, an order
. The order was composed mostly of sea snails, but it also included some land snails and freshwater snails, all of which were prosobranch gastropod mollusks.
This order was introduced by J. Thiele
in his work from 1921, it and was used for many decades subsequently.
Recent research in malacology
however has made it clear that Mesogastropoda was not a monophyletic taxon
, and because of that, the taxon
is no longer included in modern classifications. Nonetheless most of the standard texts and field guide
s on mollusks date from the time period when this classification was still current, and therefore references to mesogastropods or Mesogastropoda are frequently encountered.
The lower taxa that were traditionally contained in Mesogastropoda are now mostly placed in the superorder Caenogastropoda
. A more detailed account of the taxonomy is given in the articles on Gastropoda
and Archaeogastropoda
, and a recent taxonomy is laid out in Taxonomy of the Gastropoda (Bouchet & Rocroi, 2005)
.
Most of these snails are herbivorous
, but a few are parasites or predators. The radula
has seven denticles (or small teeth), which are sometimes reduced.
The Mesogastropoda are, in many ways, more developed than the Archaeogastropoda
. Through torsion of the intestinal mass and a spiral movement of the body, the gill
, the kidney
and the osphradium (which means sensory receptor, or olfactory organ) have disappeared on the right side. These organs exist only on the left side of the animal.
The heart consists of only one atrium
and one ventricle
.
The nervous system
is also more developed than in the Archeogastropods. The ganglia
are connected with different organs through nerve pathways.
In the Mesogastropoda, the execretory and the reproductive ducts are separated (in contrast with the most primitive prosobranchs). Many members produce egg capsules, containing one to more than 1,000 eggs.
) (which is no longer considered valid).
The next taxonomy that was used was that of to Ponder & Lindberg, 1997
.
The current prevailing system of taxonomy is that of Bouchet & Rocroi, 2005
.
Snail
Snail is a common name applied to most of the members of the molluscan class Gastropoda that have coiled shells in the adult stage. When the word is used in its most general sense, it includes sea snails, land snails and freshwater snails. The word snail without any qualifier is however more often...
s, an order
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
. The order was composed mostly of sea snails, but it also included some land snails and freshwater snails, all of which were prosobranch gastropod mollusks.
This order was introduced by J. Thiele
Johannes Thiele
Johannes Thiele, full name Karl Hermann Johannes Thiele was a German zoologist specialized in malacology. His Handbuch der systematischen Weichtierkunde is a standard work...
in his work from 1921, it and was used for many decades subsequently.
Recent research in malacology
Malacology
Malacology is the branch of invertebrate zoology which deals with the study of the Mollusca , the second-largest phylum of animals in terms of described species after the arthropods. Mollusks include snails and slugs, clams, octopus and squid, and numerous other kinds, many of which have shells...
however has made it clear that Mesogastropoda was not a monophyletic taxon
Taxon
|thumb|270px|[[African elephants]] form a widely-accepted taxon, the [[genus]] LoxodontaA taxon is a group of organisms, which a taxonomist adjudges to be a unit. Usually a taxon is given a name and a rank, although neither is a requirement...
, and because of that, the taxon
Taxon
|thumb|270px|[[African elephants]] form a widely-accepted taxon, the [[genus]] LoxodontaA taxon is a group of organisms, which a taxonomist adjudges to be a unit. Usually a taxon is given a name and a rank, although neither is a requirement...
is no longer included in modern classifications. Nonetheless most of the standard texts and field guide
Field guide
A field guide is a book designed to help the reader identify wildlife or other objects of natural occurrence . It is generally designed to be brought into the 'field' or local area where such objects exist to help distinguish between similar objects...
s on mollusks date from the time period when this classification was still current, and therefore references to mesogastropods or Mesogastropoda are frequently encountered.
The lower taxa that were traditionally contained in Mesogastropoda are now mostly placed in the superorder Caenogastropoda
Caenogastropoda
Caenogastropoda is a taxonomic clade of a large diverse group of mostly marine gastropods.Caenogastropoda contains a majority of the families of shelled marine molluscs including such families as the periwinkles, cowries, wentletraps, moon snails, and cone snails.About 60% of all living gastropods...
. A more detailed account of the taxonomy is given in the articles on Gastropoda
Gastropoda
The Gastropoda or gastropods, more commonly known as snails and slugs, are a large taxonomic class within the phylum Mollusca. The class Gastropoda includes snails and slugs of all kinds and all sizes from microscopic to quite large...
and Archaeogastropoda
Archaeogastropoda
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...
, and a recent taxonomy is laid out in Taxonomy of the Gastropoda (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...
Description
There are about 30,000 species that were included in this taxon. Most of them are to be found in the sea, but there are also numerous species in freshwater and even a few occur on land. Their shells have no mother-of-pearl or nacreNacre
Nacre , also known as mother of pearl, is an organic-inorganic composite material produced by some mollusks as an inner shell layer; it is also what makes up pearls. It is very strong, resilient, and iridescent....
.
Most of these snails are herbivorous
Herbivore
Herbivores are organisms that are anatomically and physiologically adapted to eat plant-based foods. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in...
, but a few are parasites or predators. The radula
Radula
The radula is an anatomical structure that is used by molluscs for feeding, sometimes compared rather inaccurately to a tongue. It is a minutely toothed, chitinous ribbon, which is typically used for scraping or cutting food before the food enters the esophagus...
has seven denticles (or small teeth), which are sometimes reduced.
The Mesogastropoda are, in many ways, more developed than the Archaeogastropoda
Archaeogastropoda
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...
. Through torsion of the intestinal mass and a spiral movement of the body, the gill
Gill
A gill is a respiratory organ found in many aquatic organisms that extracts dissolved oxygen from water, afterward excreting carbon dioxide. The gills of some species such as hermit crabs have adapted to allow respiration on land provided they are kept moist...
, the kidney
Kidney
The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...
and the osphradium (which means sensory receptor, or olfactory organ) have disappeared on the right side. These organs exist only on the left side of the animal.
The heart consists of only one atrium
Heart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...
and one ventricle
Heart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...
.
The nervous system
Nervous system
The nervous system is an organ system containing a network of specialized cells called neurons that coordinate the actions of an animal and transmit signals between different parts of its body. In most animals the nervous system consists of two parts, central and peripheral. The central nervous...
is also more developed than in the Archeogastropods. The ganglia
Ganglion
In anatomy, a ganglion is a biological tissue mass, most commonly a mass of nerve cell bodies. Cells found in a ganglion are called ganglion cells, though this term is also sometimes used to refer specifically to retinal ganglion cells....
are connected with different organs through nerve pathways.
In the Mesogastropoda, the execretory and the reproductive ducts are separated (in contrast with the most primitive prosobranchs). Many members produce egg capsules, containing one to more than 1,000 eggs.
Taxonomy
Here follows the taxonomy of the Mesogastropoda (according to the ITISIntegrated Taxonomic Information System
The Integrated Taxonomic Information System is a partnership designed to provide consistent and reliable information on the taxonomy of biological species. ITIS was originally formed in 1996 as an interagency group within the U.S...
) (which is no longer considered valid).
The next taxonomy that was used was that of to Ponder & Lindberg, 1997
Taxonomy of the Gastropoda (Ponder & Lindberg, 1997)
The taxonomy of the Gastropoda, as revised by Winston Ponder and David R. Lindberg in 1997, is an older taxonomy of the class Gastropoda, the class of molluscs consisting of all snails and slugs...
.
The current prevailing system of taxonomy is that 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
- AbyssochrysidaeAbyssochrysidaeAbyssochrysidae is a family of sea snails, marine gastropod mollusks in the clade Caenogastropoda .- Taxonomy :...
- AciculidaeAciculidaeThe Aciculidae are a family of minute land snails which have opercula. In other words, Aciculidae are terrestrial operculate gastropods....
- AporrhaidaeAporrhaidaeAporrhaidae, common name the pelican's foot snails, is a taxonomic family of sea snails. The taxonomy of the Gastropoda by Bouchet & Rocroi, 2005 categorizes Aporrhaidae as marine gastropod mollusks in the clade Littorinimorpha....
MörchOtto Andreas Lowson MörchOtto Andreas Lowson Mörch was a biologist, specifically a malacologist. He lived in Sweden, in Denmark, and in France.- Taxa described :Bibliography and taxa described by Otto Andreas Lowson Mörch include:...
, 1852 - Asterophilidae
- Chondropomidae
- Choristeidae (the original name Choristidae was a name to be emended to Choristeidae by the ICZN to remove homonymy with ChoristidaeChoristidaeChoristidae is a small family of scorpionflies known only from Australia. Their larvae are found in moss mats.-Species:* Chorista Klug, 1838* Chorista australis Klug, 1838* Chorista luteola...
, a family of scorpionflies) - CingulopsidaeCingulopsidaeCingulopsidae is a family of sea snails, marine gastropod molluscs in the clade Littorinimorpha.According to taxonomy of the Gastropoda by Bouchet & Rocroi the family Cingulopsidae has no subfamilies.- Genera and species :...
- CochlostomatidaeCochlostomatidaeCochlostomatinae are a subfamily of small land snails which have operculums and gills. These are terrestrial gastropod mollusks in the family Diplommatinidae.-Distribution:These snails live in the limestone mountains of southern Europe and North Africa....
- Diastomidae Cossman, 1895
- Fossaridae Trachel, 1861
- HydrococcidaeHydrococcidaeHydrococcidae is a family of small sea snails, marine gastropod molluscs in the clade Littorinimorpha.-Genera:* Hydrococcus Thiele, 1928** Hydrococcus brazieri : synonym : Assiminea brazieri - References :*...
- IravadiidaeIravadiidaeIravadiidae is a family of minute sea snails, marine gastropod molluscs in the superfamily Rissooidea and the clade Littorinimorpha.-Genera :Genera within the family Iravadiidae include:* Acliceratia Ponder, 1984* Ceratia H. & A. Adams, 1852...
- Lacunidae Gill, 1871
- LittorinidaeLittorinidaeLittorinidae is a taxonomic family of over 200 species of sea snails, marine gastropod molluscs in the clade Littorinimorpha, commonly known as periwinkles and found world-wide.-Names:...
Gray, 1840 - MelanopsidaeMelanopsidaeMelanopsidae, common name melanopsids, is a family of freshwater gastropods in the clade Sorbeoconcha. Species in this family are native to southern and eastern Europe, northern Africa, parts of the Middle East, New Zealand, and freshwater streams of some large South Pacific islands.These snails...
- Micromelaniidae
- OmalaxidaeOmalaxidaeOmalaxidae is an extinct family of sea snails, marine gastropod molluscs in the clade Littorinimorpha....
- Paedophoropodidae
- Pilidae
- PomatiopsidaePomatiopsidaePomatiopsidae is a family of small mainly freshwater snails with gills and an operculum, aquatic gastropod mollusks in the superfamily Rissooidea ....
- Pseudosacculidae
- StenothyridaeStenothyridaeStenothyridae is a family of freshwater snails, snails with gills and an operculum, aquatic gastropod mollusks in the superfamily Rissooidea.This family has no subfamilies.-Distribution :...
- StiliferidaeStiliferidaeStiliferidae is a taxonomic family of small parasitic sea snails, marine gastropod molluscs in the superfamily Eulimoidea.-Genera:Genera within the family Stiliferidae include:* Athleenia * Mucronalia * Stilifer Broderip and Sowerby, 1832...
- Struthiolariidae
- Syrnolopsidae
- Trachysmidae
- Trochaclisidae
- Superfamily CyclophoroideaCyclophoroideaCyclophoroidea is a superfamily of land snails with an operculum, terrestrial gastropods within the informal group Architaenioglossa, that belongs to the clade Caenogastropoda....
- Superfamily ViviparoideaViviparoideaCyclophoroidea is a taxonomic superfamily of freshwater snails, aquatic gastropod mollusks within the informal group Architaenioglossa, which belongs to the clade Caenogastropoda....