Sea angel
Clione limacina, the largest species of snails rudder
The rowing screw ( Gymnosomata formed from ancient Greek γυμνός Gymnos "naked" and ancient Greek τό σωμάτιον tó somátion " small body", literally " naked body " ) are a suborder of the pelagic opisthobranch. The rowing screw are all very small: the largest species, Clione limacina, measuring up to 5 cm.
Features
In adapting to their pelagic bilaterally symmetrical, usually colorless, transparent rowing screws have no shell. Your foot is in the form of two wing-shaped flaps ( parapodia ), with which they actively move by rowing movements. Despite their outward similarity, they are not more closely related to the Thecosomata. At speed in rowing, they surpass this clearly.
The rowing screw capture using tentacle -like appendages on zooplankton mouth, often worm of subordination Thecosomata.
System
The taxonomy of the worm is subject to revision and change. Therefore, there are different classifications. On J. Thiele (1929-1935) is usually considered going back as classical. She was recognized until the 1990s. A more modern and the last established on purely morphological approaches to systematics is that of Ponder & Lindberg (1997). The current system is phylogenetically oriented and goes back to Bouchet & Rocroi ( 2005).
The Gymnosomata once part of the existing to the 20th century group of pteropods ( Pteropoda ). The Pteropoda formed late 19th century, an order of Gastropoda, early 20th century, even its own class of molluscs. In more modern taxonomies the Gymnosomata form a subordination or occupy a comparable rank.
Bouchet & Rocroi classification by (2005)
- Class Gastropoda Cuvier, G., 1797 Clade Heterobranchia J. E. Gray, 1840 informal group Opisthobranchia H. Milne Edwards, 1848 Clade Gymnosomata H.D.M. de Blainville, 1848 Superfamily Clionoidea C. S. Rafinesque, 1815 Family Clionidae C. S. Rafinesque, 1815
- Family Cliopsidae Costa, 1873
- Family Notobranchaeidae Pelseneer, 1886
- Family Pneumodermatidae P. A. Latreille, 1825
- Family Hydromylidae A. Pruvot -Fol, 1942
- Family Laginiopsidae A. Pruvot -Fol, 1922
Compared to Ponder & Lindberg (1997 ), a more pronounced structuring of the families into two superfamilies. The previous family Thliptodontidae ( Kwietniewski, 1910) loses its self is managed in this system, as a subfamily Thliptodontinae the Clionidae family.
Classification by Ponder & Lindberg (1997)
- Class Gastropoda Cuvier, G., 1797 Subclass Orthogastropoda W. F. Ponder & D. R. Lindberg, 1996 Subclass Apogastropoda L. Salvini - Plawen & G. Haszprunar, 1987 Superorder Heterobranchia J. E. Gray, 1840 Group Euthyneura J. W. Spengel, 1881 H. Milne Edwards order Opisthobranchia, 1848 Subordination Gymnosomata H.D.M. de Blainville, 1848 Family Clionidae C. S. Rafinesque, 1815
- Family Cliopsidae Costa, 1873
- Family Hydromylidae A. Pruvot -Fol, 1942
- Family Laginiopsidae A. Pruvot -Fol, 1922
- Family Notobranchaeidae Pelseneer, 1886
- Family Pneumodermatidae P. A. Latreille, 1825
- Family Thliptodontidae Kwietniewski, 1910
Sources and Literature
- Mollusca - The Southern Synthesis Order Gymnosomata by L. Newman pages 985-989; Beesley, P. L., Ross, G.J.B. & Wells, A ( eds ) - ISBN 0-643-05756-0