''Syrnola thelma'' is an extinct
species
A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...
of
sea snail
Sea snails are slow-moving marine (ocean), marine gastropod Mollusca, molluscs, usually with visible external shells, such as whelk or abalone. They share the Taxonomic classification, taxonomic class Gastropoda with slugs, which are distinguishe ...
, a
marine gastropod
Gastropods (), commonly known as slugs and snails, belong to a large Taxonomy (biology), taxonomic class of invertebrates within the phylum Mollusca called Gastropoda ().
This class comprises snails and slugs from saltwater, freshwater, and fro ...
mollusk
Mollusca is a phylum of protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant species of molluscs are recognized, making it the second-largest animal phylum after Arthropoda. The ...
in the
family
Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...
Pyramidellidae
Pyramidellidae, common name the pyram family, or pyramid shells, is a voluminous taxonomic family of mostly small and minute ectoparasitic sea snails, marine heterobranch gastropod molluscs. The great majority of species of pyrams are micromol ...
, the pyrams and their allies.
[W.H. Dall (1913), ''On a Brackish Water Pliocene Fauna of the Southern Coastal Plain''; Proceedings U. S. National Museum, Vol. 46—No. 2023]
Description
The small shell has an elongate-conic shape. It has a smooth appearance, except for incremental lines. The
suture is distinct but not deep. The
apical portion is decollate. The
aperture
In optics, the aperture of an optical system (including a system consisting of a single lens) is the hole or opening that primarily limits light propagated through the system. More specifically, the entrance pupil as the front side image o ...
is narrowly ovate. The
outer lip is simple and blunt. The base of the shell rounds into a strongly twisted short pillar. The body of the shell has no visible callus. The length of decollate fragment (two whorls) measures 2 mm, the diameter 1 mm.
Distribution
A fragment of the shell of this brackish water species has been found near
Alexandria
Alexandria ( ; ) is the List of cities and towns in Egypt#Largest cities, second largest city in Egypt and the List of coastal settlements of the Mediterranean Sea, largest city on the Mediterranean coast. It lies at the western edge of the Nile ...
, Louisiana.
References
External links
Paleobiology database : ''Syrnola thelma''
{{Taxonbar, from=Q7663479
Pyramidellidae
Gastropods described in 1913