Annulariidae

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Phylum:Mollusca
Class:Gastropoda
Subclass:Caenogastropoda
Order:Littorinimorpha
Annulariidae
Shell of Gouldipoma chiapasense (syntype at MNHN, Paris)
Scientific classification Edit this classification
Kingdom: Animalia
Phylum: Mollusca
Class: Gastropoda
Subclass: Caenogastropoda
Order: Littorinimorpha
Superfamily: Littorinoidea
Family: Annulariidae
Henderson & Bartsch, 1920
Type species
Annularia
Genera

See text

The family Annulariidae is a taxonomic family of small operculate land snails in the superfamily Littorinoidea.[1]

(Original description) This family encompasses all New World "Cyclostomoid" mollusks previously classified under the family names Cyclostomatidae or Eriidae.

Key Distinguishing Characteristics: The primary feature that separates this family from all other operculate pulmonates is found in the radula (the rasping tongue), which exhibits a fundamental uniformity across the large number of included species.

Radula Structure
the radula possesses a consistent tooth arrangement:
  • Rachidian tooth: single and unicuspid.
  • Lateral tooth: single and unicuspid.
  • Inner marginal tooth: resembles the lateral tooth in form but is multicuspid.
  • Outer Mmrginal tooth: long and curved like a bow (arcuate). It is pectinated (comb-like) on both its recurved edge and its main portion, but these pectinations do not divide it into individual teeth.
  • Jaw: absent.
Foot and progression
The sole of the foot is longitudinally divided by a sulcus (groove), which separates it into two muscular masses. These two masses function independently, allowing the animal a method of progression by alternate waves of muscular contraction (first on one side, then on the other). The foot is relatively short.
Head and sensory organs
  • Muzzle: a bifid (forked) muzzle of varying length is always present.
  • Tentacles: they are long, slender, and either fibrillar or slightly swollen at the ends.
  • Eyes: The eyes are situated at the base of the tentacles on the outer side. They are often raised above the surface of the head by a fleshy protuberance.
Operculum
The operculum displays a wide degree of variation across the family's divisions, yet it follows distinct evolutionary lines of progression. The structure ranges from a simple type to a highly complicated one, with intermediate steps easily traceable. All opercula possess a basal chondroid plate (cartilaginous base) upon which calcareous ribs and lamellae (thin plates) are deposited. Modifications of these calcareous structures are used to subdivide the family into a series of subfamilies and genera, as will be discussed below.
Shell
The shell shape varies widely, from depressed helicoid (flat, spiral like a snail) to elongate conic. The surface sculpture varies greatly: from axially ribbed only to axially ribbed and spirally lirate (with fine spiral lines). The intensity of these elements ranges from obsolete (faint) to lamellose (layered/plate-like).[2]

Genera

Subfamily Abbottellinae Watters, 2016
Subfamily Annulariinae Henderson & Bartsch, 1920
Subfamily Chondropomatinae Henderson & Bartsch, 1920
Subfamily Rhytidopomatinae Henderson & Bartsch, 1920
Subfamily Tudorinae Watters, 2006

Distribution

References

External links

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