Euomphaloidea, originally Euomphalacea, is an

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

superfamily of

marine Marine is an adjective meaning of or pertaining to the sea or ocean. Marine or marines may refer to: Ocean * Maritime (disambiguation) * Marine art * Marine biology * Marine debris * Marine habitats * Marine life * Marine pollution Military * ...

mollusc Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is esti ...

s that lived from the Early Ordovician to the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', the ...

, included in the Gastropoda Moore R. C., Lalicker & Fischer (1952). ''Invertebrate Fossils''. McGraw-Hill publisher. but speculated as instead perhaps Monoplacophora.

Description

Euomphaloid shells 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.(1960). ''

Treatise on Invertebrate Paleontology The ''Treatise on Invertebrate Paleontology'' (or ''TIP'') published by the Geological Society of America and the University of Kansas Press, is a definitive multi-authored work of some 50 volumes, written by more than 300 paleontologists, and co ...

. Part I, Gastropoda.

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.

Taxonomy of the Treatise 1960

J. Brooks Knight, ''et al'', 1960, in the

, Part I, included the Euomphalacea, as then used, in the suborder Macluritina, deriving them from the Macluritacea, and included the following three families.
:

Euomphalidae Euomphalidae is an extinct family of Paleozoic to early Mesozoic marine molluscs which may be gastropods with anisostrophically coiled shells (according to the taxonomy of the Gastropoda by Bouchet & Rocroi, 2005). The shells show a selenizone ...

de Konick, 1881 : Helicotomidae Wenz, 1938 : Omphalotrochidae Knight, 1945 Prior to, R.C. Moore in 1952, included the Euomphalacea in the gastropod order Archaeogastropoda.

More recent taxonomies

The Euomphaloidea are included in the gastropod order

Euomphalina The Euomphalina comprise a major suborder of mainly Paleozoic archaeogastropods, shells of which are hyperstophic to depressed orthstrophic, commonly with an angulation at the outer upper whorl surface thought to be coincident with the exhalent c ...

, subclass

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 (subclasses) of the class Gastropoda, the snails. The other subclass of ...

(revised

Prosobranchia Prosobranchia was a large taxonomic subclass of sea snails, land snails and freshwater snails. This taxon of gastropods dates back to the 1920s. It has however been proven to be polyphyletic (consisting of more than one lineage of descent). Gene ...

) according to 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. The full name of the work in which this taxonomy wa ...

. This was accepted by Wagner, (2008) revised to include the following families. :

Anomphalidae The Anomphalidae is an extinct family of fossil sea snails, marine gastropod mollusks. These are archaeogastropods which are included in the suborder Trochina. The Anomphalidae lived during the Paleozoic, from the Silurian to the Middle Permian. ...

Wenz, 1938 : Elasmonematidae Knight, 1956 :

de Koninck, 1881 : Helicotomidae Wenz, 1938 : Holopeidae Wenz, 1938 : Lesueurillidae Wagner, 1999 : Microdomatidae Wenz, 1938 : Omphalocirridae Wenz, 1938 : Omphalotrochidae Knight, 1945 : Pseudophoridae Miller, 1889 :

Raphistomatidae The †Raphistomatidae is a taxonomic family of fossil sea snails, Paleozoic marine gastropod mollusks. This family was established by Koken in 1896. This family is found in the fossil record from the Upper Cambrian to the Middle Permian. D ...

Koken, 1896 :

Tychobraheidae Tychobraheidae is an extinct family of fossil sea snails, marine gastropod mollusk Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85, ...

Horný, 1992 (excludes ''Tychobrahea'') In the meantime Boucet and Rocroi (2005)

Taxonomy of the Gastropoda (Bouchet & Rocroi, 2005) The taxonomy of the Gastropoda as it was revised in 2005 by Philippe Bouchet and Jean-Pierre Rocroi is a system for the scientific classification of gastropod mollusks. (Gastropods are a taxonomic class of animals which consists of snails and ...

classified the Eumphaloidea simply as Paleozoic molluscs with anisostrophically coiled shells of uncertain position that are possibly gastropods, recognizing only five families, the:
:

: Helicotomidae : Lesueurillidae : Omphalocirridae : Omphalotrochidae

Discussion, revised taxonomy

Prior to being included in the Euomphaloidea, the Anomphalidae, Elasmonematidae, Holopeidae, and Microdomatidae were included in the suborder Trochina, Cox & Knight 1960; the Anomphalidae in the Anomphalacea, the Elasmonematidae and Microdomatidae in the Microdomatacea, and the Holopeidae in the Plytyceratacea. The Raphystomatidae were included in the Pleurotomaracea, Pleurotomarina. '' Omphalocirrus'' is included in the Maclurridae in the Treatise, 1960, but ''Lioomphalus'', given as also in the Omphalocerridae Omphaloceriidae, Paleobio db
/ref> is a synonym for ''

Euomphalus ''Euomphalus'' is a genus of fossil marine gastropods known to have lived from the Silurian to the Middle Permian.J.B.Knight,et al 1960. Treatise on Invertebrate Paleontology, Part I, Mollusca 1, ch on systematic descriptions. Geol Soc of Amer ...

'', Euomphalidae,

References

{{Taxonbar, from=Q5409853 Prehistoric gastropods