Eogastropoda

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Eogastropoda
Common limpet (Patella vulgata)

Common limpet ( Patella vulgata )

Systematics
without rank: Bilateria
without rank: Primordial mouths (protostomia)
Over trunk : Lophotrochozoa (Lophotrochozoa)
Trunk : Molluscs (mollusca)
Class : Snails (gastropoda)
Subclass : Eogastropoda
Scientific name
Eogastropoda
Ponder & Lindberg , 1995

The Eogastropoda are a large group of snails , which today is mostly understood as a subclass. The taxa that are commonly referred to as "real limpets" Patellogastropoda as well as the extinct Euomphalida and possibly the Neomphalida are placed next to it . Compared to the other subclass Orthogastropoda , it is a much smaller part of the species of snail.

history

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 by Ponder and Lindberg 1997, the snails can therefore be 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 some taxa that were previously assigned to the Prosobranchia, but also the groups that can be called "real limpets" ( Patellogastropoda ). In addition, some extinct groups are counted among the Eogastropoda.

definition

The Eogastropoda and the Patellogastropoda are characterized by the following apomorphic features according to Ponder & Lindberg (1997). The features are usually not detectable in the fossil groups.

  • the rear housing extension is larger than the front or side housing extension
  • The protoconch is separated from the juvenile housing
  • the shell has a foliate microstructure
  • Blood vessels run through the shell muscles
  • no propodium in the adult stage
  • simple kidneys on the right side of the pericardium
  • Jaw from two lobes fused dorsally
  • the number of tooth-bearing cartilages (the radula) are reduced from 3 or more pairs to two pairs
  • Nervous system: foot nodes arranged around the foot, few connections
  • Statocysts dorsally (or slightly offset backwards) over the foot ganglia.

system

In the system of recent snails, Eogastropoda and Patellogastropoda largely correspond. The only difference between the Eogastropoda is that they also include the extinct order Euomphalida .

The order Neomphalida McLean, 1981 is also placed by some authors among the Eogastropoda. Bouchet and Rocroi (2005), however, list the group as a superfamily among the Vetigastropoda .

literature

  • Philippe Bouchet & Jean-Pierre Rocroi: Part 2. Working classification of the Gastropoda . In: Malacologia. 47: 239-283, Ann Arbor 2005 ISSN  0076-2997
  • Winston Ponder & David Lindberg, Towards a phylogeny of gastropod molluscs; an analysis using morphological characters . In: Zoological Journal of the Linnean Society. 119: 83-265, London 1997 ISSN  0024-4082

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