Euomphaloidea
Encyclopedia
Euomphaloidea, originally Euomphalacea, is an extinct superfamily of marine
molluscs that lived from the Early Ordovician to the Late Cretaceous
, included in the Gastropoda but speculated as instead perhaps Monoplacophora.
are mostly discoidal and may be either orthostrophic (coils wrapped around an erect cone) or hyperstrophic (coils wrapped around an inverted cone); are widely umbilicate and commonly have a channel, presumed exhalent, within the angulation in the outer part of the upper whorl surface. The shell wall is relatively thick, with an external prismatic layer of calcite, which may be pigmented, and an internal layer of lamellar, but not nacreous, aragonite.
In 1952, Raymond Cecil Moore
included the Euomphalacea in the gastropod order Archaeogastropoda.
and Wagner, again in 2008, included the Euomphaloidea in the order Euomphalina
, in turn in the subclass Eogastropoda
(revised Prosobranchia
), recognising them as valid taxa.
Families in the superfamily Euomphaloidea include:
Marine (ocean)
Marine is an umbrella term. As an adjective it is usually applicable to things relating to the sea or ocean, such as marine biology, marine ecology and marine geology...
molluscs that lived from the Early Ordovician to the Late Cretaceous
Late Cretaceous
The Late Cretaceous is the younger of two epochs into which the Cretaceous period is divided in the geologic timescale. Rock strata from this epoch form the Upper Cretaceous series...
, included in the Gastropoda but speculated as instead perhaps Monoplacophora.
Description
Euomphaloid shellsGastropod shell
The gastropod shell is a shell which is part of the body of a gastropod or snail, one kind of mollusc. The gastropod shell is an external skeleton or exoskeleton, which serves not only for muscle attachment, but also for protection from predators and from mechanical damage...
are mostly discoidal and may be either orthostrophic (coils wrapped around an erect cone) or hyperstrophic (coils wrapped around an inverted cone); are widely umbilicate and commonly have a channel, presumed exhalent, within the angulation in the outer part of the upper whorl surface. The shell wall is relatively thick, with an external prismatic layer of calcite, which may be pigmented, and an internal layer of lamellar, but not nacreous, aragonite.
Taxonomy
As with almost all fossils, the taxonomic relations of and within the euophaloids can only be inferred from their remaining hard parts, in their case the shell. The general inclusion of the Euomphalacea, as originally spelled is based on the asymmetrically coiled tubular shell, suggestive if not indicative of the diagnostic torsion.In 1952, Raymond Cecil Moore
Raymond Cecil Moore
Raymond Cecil Moore was an American geologist. In 1970 he was awarded the Mary Clark Thompson Medal from the National Academy of Sciences.- Bibliography :...
included the Euomphalacea in the gastropod order Archaeogastropoda.
1997 and 2008 taxonomy
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...
and Wagner, again in 2008, included the Euomphaloidea in the order Euomphalina
Euomphalina
Euomphalina, is a taxonomic order of extinct sea snails, marine gastropod mollusks, known from fossils. This order includes the extinct superfamilies Euomphaloidea, Macluritoidea, Ophiletoidea, and Platyceratoidea....
, in turn in the subclass Eogastropoda
Eogastropoda
Eogastropoda was a previously used taxonomic category of snails or gastropods, a subclass which was erected by Ponder and Lindberg in 1997. It was one of two great divisions of the class Gastropoda, the snails. The other subclass of gastropods was the Orthogastropoda.Eogastropoda were the more...
(revised Prosobranchia
Prosobranchia
Not to be confused with the bivalve order Protobranchia.Prosobranchia was a large taxonomic subclass of sea snails, land snails and freshwater snails. This taxon of gastropods dates back to the 1920s...
), recognising them as valid taxa.
Families in the superfamily Euomphaloidea include:
- AnomphalidaeAnomphalidae†Anomphalidae is an extinct family of paleozoic gastropod mollusks of basal taxa that are certainly Gastropoda .- Taxonomy :...
Wenz, 1938 - ElasmonematidaeElasmonematidaeElasmonematidae is an extinct family of gastropods in the clade Vetigastropoda .This family has no subfamilies.- Genera :Genera within this family include:...
Knight, 1956 - EuomphalidaeEuomphalidaeEuomphalidae is an extinct family of Paleozoic molluscs which may possibly be gastropods with anisostrophically coiled shells .- Genera :Genera in the family Euomphalidae include:...
de Koninck, 1881 - HelicotomidaeHelicotomidaeHelicotomidae is an extinct family of Paleozoic molluscs with anisostrophically coiled shells of uncertain position .- Taxonomy :...
Wenz, 1938 - HolopeidaeHolopeidae†Holopeidae is an extinct family of paleozoic gastropod mollusks.This family is unassigned to superfamily. This family has no subfamilies....
Wenz, 1938 - LesueurillidaeLesueurillidaeLesueurillidae is an extinct family of paleozoic molluscs with anisostrophically coiled shells of uncertain position .- Taxonomy :...
Wagner, 1999 - MicrodomatidaeMicrodomatidaeMicrodomatidae is an extinct family of fossil sea snails, marine gastropod mollusks in the superfamily Trochoidea .- Taxonomy :...
Wenz, 1938 - OmphalocirridaeOmphalocirridaeOmphalocirridae is an extinct family of paleozoic molluscs with anisostrophically coiled shells of uncertain position .- Taxonomy :...
Wenz, 1938 - OmphalotrochidaeOmphalotrochidaeOmphalotrochidae is an extinct family of paleozoic molluscs with anisostrophically coiled shells of uncertain position .- Taxonomy :...
Knight, 1945 - PseudophoridaePseudophoridaePseudophoridae is an extinct family of paleozoic gastropod mollusks.This family is unassigned to superfamily. This family has no subfamilies....
Miller, 1889 - RaphistomatidaeRaphistomatidaeThe Raphistomatidae is a family of Paleozoic gastropods established by Koken, 1896, whose range extends from the Upper Cambrian to Middle Permian, comprising lentuclar, turbiniform, and stepped shells with a short slit, notch, or sinus on the aperture lip that generally results in a selenizone.J...
Koken, 1896 - "TychobraheidaeTychobraheidaeTychobraheidae is an extinct family of gastropods in the clade Vetigastropoda .This family has no subfamilies....
" Horný, 1992 (excludes Tychobrahea)
2005 taxonomy
Boucet and Rocroi (2005) classified Euomphaloidea as Paleozoic molluscs with anisostrophically coiled shells of uncertain position (Gastropoda?). Families in the superfamily Euomphaloidea include:- † EuomphalidaeEuomphalidaeEuomphalidae is an extinct family of Paleozoic molluscs which may possibly be gastropods with anisostrophically coiled shells .- Genera :Genera in the family Euomphalidae include:...
- † HelicotomidaeHelicotomidaeHelicotomidae is an extinct family of Paleozoic molluscs with anisostrophically coiled shells of uncertain position .- Taxonomy :...
- † LesueurillidaeLesueurillidaeLesueurillidae is an extinct family of paleozoic molluscs with anisostrophically coiled shells of uncertain position .- Taxonomy :...
- † OmphalocirridaeOmphalocirridaeOmphalocirridae is an extinct family of paleozoic molluscs with anisostrophically coiled shells of uncertain position .- Taxonomy :...
- † OmphalotrochidaeOmphalotrochidaeOmphalotrochidae is an extinct family of paleozoic molluscs with anisostrophically coiled shells of uncertain position .- Taxonomy :...