Pseudothecosomata, common name sea butterflies, is or was, a taxonomic suborder or infraorder of floating and swimming sea snails or sea slugs, pelagic marine opisthobranch gastropod mollusks.
The taxon Pseudothecosomata Meisenheimer, 1905 was established at an unspecified rank above family, and it originally contained the families Cymbuliidae and Desmopteridae. In 1926 this taxon was treated by Thiele as a superfamily, but since the name Pseudothecosomata was not based on the name of a genus, it is not available as such.
Therefore, in the new taxonomy of Bouchet & Rocroi (2005), the taxon Pseudothecosomata is no longer recognized. Instead its three families are categorized within the superfamily Cymbulioidea, which is itself part of the clade Thecosomata.
Some groups within this suborder possess a shell, some are without, and others have developed a relatively tough gelatinous, cartilaginous internal structure, a sort of fake shell called the pseudoconch.
The lateral and posterior foot lobes are joined as a ciliated proboscis that leads to the mouth, and the wings are united ventrally to form a single plate.
A more general description of the pseudothecosomes is given under the entry sea butterfly.
Families, and genera within the suborder Pseudothecosomata
Descriptions of taxa
Family Peraclidae Tesch, 1913
This family was originally called Procymbuliidae Tesch, 1913 and then called Peraclididae by Wenz in 1938. The name Peraclidae takes precedence.
The left-coiled shell resembles the shell of most snails. The columella is somewhat elongated into a curved rostrum. There is an operculum and a gill.
Genus Peracle Forbes, 1844
- Peracle apicifulva Meisenheimer, 1906 (synonym of Peracle diversa)
- Peracle bispinosa Pelseneer, 1888 -- Two-spine pteropod
- Distribution : Florida, Bermudas, Cuba, Venezuela, Oceanic.
- Length : 7.5 mm
- Peracle depressa Meisenheimer, 1906
- Distribution : Cuba, Brazil, Argentina, Oceanic, Equatorial Atlantic
- Peracle diversa di Monterosato, 1875
- Distribution : Florida, Bermuda, Cuba, Argentina, Mediterranean
- Length : 4 mm
- Peracle moluccensis Tesch, 1903
- Distribution : Panama, Brazil, British Isles, Oceanic
- Length : 3 mm
- Peracle philiporum R.W. Gilmer, 1990
- Distribution : Bahamas
- Length : 4.5 mm
- Peracle reticulata (d'Orbigny, 1836) Reticulate pteropod
- Distribution : Oceanic, Florida, Texas; Mediterranean
- Length : 6 mm
- Description : the shell, which shows a hexagonal pattern, is rather heavy and compels this little animal to flap continuously to keep afloat.
- Peracle triacantha P. Fischer, 1882
- Distribution : Oceanic, Cuba, Bermuda, Venezuela, Mediterranean
- Length : 5 mm
- Peracle valdiviae Meisenheimer 1905
- Distribution : Oceanic, Argentina
- Length : 5 mm
Family Cymbuliidae J.E. Gray, 1840
Instead of an external calcareous shell, they possess a pseudoconch, consisting of conchioline, a cartilaginous tissue. The mantle and the gill have disappeared as well. They breathe through the skin. They prefer warm water. In Europe, they can only be found in the Mediterranean.
Subfamily Cymbuliinae Gray, 1840
Genus Corolla (Dall, 1871
They are preyed upon by the gymnosome pteropods of the genus Cliopsis.
- Corolla calceola (A. E. Verrill, 1880) -- Atlantic corolla
- Distribution : Oceanic
- Length : 40 mm
- Corolla intermedia (Tesch, 1903)
- Distribution : Florida, Oceanic
- Length : 39 mm
- Corolla ovata Quoy & Gaimard, 1832
- Distribution : Florida, Bermuda, Oceanic
- Length : 40 mm
- Corolla spectabilis (Dall, 1871) Spectacular corolla
- Distribution : Florida, Bermuda, Venezuela, Brazil, Oceanic.
- Length : 40 mm
Genus Cymbulia Peron and Lesueur, 1810
- Cymbulia parvidentata Pelseneer, 1888
- Distribution : Bermuda, Oceanic
- Length : 35 mm
- Cymbulia peronii de Blainville, 1818
- Distribution : Florida, Mexico, Brazil, Argentina, Oceanic
- Length : 65 mm
- Cymbulia sibogae Tesch, 1904
- Distribution : Brazil, Argentina, Oceanic
- Length : 24 mm
Subfamily Glebinae van der Spoel, 1976
Genus Gleba Forsskål, 1776
Family Desmopteridae (Dall, 1921)
Genus Desmopterus Chun, 1889
The species are protandric hermaphrodites. There is no shell, no protoconch and no longer any supporting tissue. The body consists almost completely of the two big parapodia (winglike flaps).
- Desmopterus cirropterus Gegenbaur, 1855
- Desmopterus gardineri Tesch, 1910
- Distribution : Indian Ocean.
- Desmopterus pacificus Essenberg, 1919
- Distribution : California, Oceanic
- Description : shorter wing plate tentacles.
- Desmopterus papilio Chun, 1889
- Distribution : Seychelles, Florida, Bermuda, Venezuela, Brazil, Adriatic Sea, tropical and subtropical oceanic waters.
- Length: body length between 0.5 – 2.0 mm, swimming wings between 2.0- 4.0 mm.
- Description : There is no shell. The animal has wings that are disc-shaped and transparent. The body is large and situated centrally between the lateral wings. These can unite to form a plate with on each side long, ciliated tentacles trailing behind. Most of the time, Desmopterus papilio hangs motionless, but flaps away in a loop pattern when disturbed. There are reddish-brown spots at the margin of the wings.
- Lalli, C.M. & Gilmer, R.W. (1989) Pelagic Snails. The biology of holoplanktonic gastropod molluscs. Stanford University Press: Stanford, California.
- Giovine, F., 1988. The genus Peracle in the Mediterranean (Heterobranchia: Peraclidae). -- La Conchiglia, 20(226-227): 22-24, 5 figs.
- Sakthivel, M., 1972. Studies on Desmopterus Chun, 1889 species in the Indian Ocean. -- 'Meteor' Forschungsergebnisse, (D)10: 46-57, 8 figs.