Orthogastropoda

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Orthogastropoda
Cone snail (Conus geographus)

Cone snail ( Conus geographus )

Systematics
without rank: Bilateria
without rank: Primordial mouths (protostomia)
Over trunk : Lophotrochozoa (Lophotrochozoa)
Trunk : Molluscs (mollusca)
Class : Snails (gastropoda)
Subclass : Orthogastropoda
Scientific name
Orthogastropoda
WF Ponder & DR Lindberg , 1996

The Orthogastropoda ( real snails ) form a taxon that was introduced by WF Ponder and DR Lindberg (1996); it is equivalent to the taxon Flexiglossata proposed by G. Haszprunar (1988) without definition.
Together with the taxon Eogastropoda ( early snails ), the Orthogastropoda form a monophyletic subdivision of snails and solve the problem of paraphyly of the prosobranchia of the systematics used until then. The taxon is part ( subclass ) of the systematics by Ponder & Lindberg (1997).
With the greater use of genetic engineering methods and more recent results, the cladistic, phylogenetic system was established by Bouchet & Rocroi (2005), which replaced the system by Ponder & Lindberg (1997). The Orthogastropoda are no longer included in this system .
The Orthogastropoda thus only form a temporary taxon , the use of which is restricted to the system of Ponder & Lindberg (1997).

Evolution of the taxon

G. Haszprunar (1988) and Ponder and Lindberg (1997) demonstrated that the previous large group of Prosobranchia within snails is paraphyletic . According to the rules of cladistics, a paraphyletic group must be resolved and divided into monophyletic groups. According to the cladistic analysis of Ponder and Lindberg (1997), the snails are therefore divided into two large groups: the Orthogastropoda and the Eogastropoda . They can be treated as subclasses in the linear-hierarchical sense. The Orthogastropoda contain part of the so-called prosobranchia as well as the opisthobranchia and the pulmonates . The subclass of the Eogastropoda also contains taxa that were assigned to the Prosobranchia, but also the groups that can be called "real limpets" ( Patellogastropoda ).

definition

The monophyly of the Orthogastropoda is based on a total of 15 synapomorphies . The most important are:

  • a radula consisting of a flexible radula membrane ("flexiglossate radula"; hence the equivalent name Flexiglossata)
  • the protoconch is separated from the juvenile housing
  • In the adult stage there was originally an operculum (reduced in many groups)
  • a simple, left hypobranchial gland ( secretion organ - in the purple snail the purple pigment is created from the secretion of this gland)
  • Propodium with Fußdrüsen
  • Vitreous eyes
  • Pair of jaws not connected to the buccal apparatus
  • a simple kidney on the right side of the pericardium
  • an unpaired osphradium (organ of smell)
  • ciliate zones on both sides of the osphradium
  • an unpaired ctenidium ( gill )

Systematics

In the system of Ponder & Lindberg (1997) the Orthogastropoda are subdivided into 6 superordinate orders and a special taxon incertæ sedis for unassigned taxa. Within the 6 superorders which has superiority of "Hot Vent Taxa" also has a special status.

Other superordinate groups have been proposed among the fossil groups .

In the system of Bouchet & Rocroi (2005) the five established superordinates move up in the hierarchy and become clades . The "Hot Venta taxa" are included in the Vetigastropoda clade . The parentage Patellogastropoda from the subclass Eogastropoda becomes the sixth clade .

Individual evidence

  1. ↑ J. Thiele (1929-1935). Manual of systematic molluscology. 2 volumes. 1-1154.
  2. ^ R. Bieler & PM Mikkelsen (Sci.Ed.); JS Bhatti (Transl.); J. Thiele Handbook of Systematic Molluscology. English: Handbook of systematic malacology. Publ: Washington, DC; Smithsonian Institution Libraries; National Science Foundation; 1992-. Content: pt. 1. Loricata; Gastropoda: Prosobranchia - pt. 2. Gastropoda: Opisthobranchia and Pulmonata - pt. 3. Scaphopoda / Bivalvia / Cehalopoda - pt. 4. Comparative Morphology / Phylogeny / Geographical Distribution. Catalog-No: OCLC 16004796 .
  3. ^ A b W. F. Ponder & DR Lindberg (1997). Towards a phylogeny of gastropod molluscs: an analysis using morphological characters. In: Zoological Journal of the Linnean Society. 119 (2): 83-265. doi : 10.1111 / j.1096-3642.1997.tb00137.x .
  4. ↑ a b P. Bouchet, & J.-P. Rocroi: Part 2. Working classification of the Gastropoda. In: Malacologia. 47: 239-283; Ann Arbor 2005; ISSN  0076-2997
  5. ↑ a b P. Bouchet & J.-P. Rocroi (Ed.): J. Frýda, B. Hausdorf, WF Ponder, Á. Valdés & A. Warén (2005). Classification and nomenclator of gastropod families. In: Malacologia: International Journal of Malacology. 47 (1-2). ConchBooks: Hackenheim, Germany. ISBN 3-925919-72-4 . ISSN 0076-2997 . 397 pages. http://www.vliz.be/Vmdcdata/imis2/ref.php?refid=78278  
  6. ↑ a b GT Poppe, & SP Tagaro: February 23, 2006; The New Classification of Gastropods according to Bouchet & Rocroi, 2005. online ( Memento of the original of September 27, 2007 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. (PDF; 191 kB). @1@ 2Template: Webachiv / IABot / www.journal-malaco.fr
  7. ↑ G. Haszprunar: On the origin and evolution of major gastropods group, with special reference to the streptoneura. In: J. Moll. Stud. 54: 367-441; 1988, doi : 10.1093 / mollus / 54.4.367 .

literature

Web links