''Amastra knudsenii'' is a

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 air-breathing

land snail A land snail is any of the numerous species of snail that live on land, as opposed to the sea snails and freshwater snails. ''Land snail'' is the common name for terrestrial molluscs, terrestrial gastropod mollusks that have gastropod shell, shel ...

, a

terrestrial Terrestrial refers to things related to land or the planet Earth, as opposed to extraterrestrial. Terrestrial may also refer to: * Terrestrial animal, an animal that lives on land opposed to living in water, or sometimes an animal that lives on o ...

pulmonate Pulmonata or pulmonates is an informal group (previously an order, and before that, a subclass) of snails and slugs characterized by the ability to breathe air, by virtue of having a pallial lung instead of a gill, or gills. The group inclu ...

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 ...

mollusc Mollusca is a phylum of protostome, protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant taxon, extant species of molluscs are recognized, making it the second-largest animal phylum ...

in the family

Amastridae Amastridae is a Taxonomy (biology), taxonomic family (biology), family of small, air-breathing, land snails, Terrestrial animal, terrestrial pulmonate gastropod mollusks in the superfamily Pupilloidea.MolluscaBase eds. (2021). MolluscaBase. Amast ...

Description

The length of the shell attains 33 mm, its diameter 17 mm. (Later supplemental description by Hyatt, A. & Pilsbry, H. A. ) The shell is imperforate, dextral, and oblong-conic, with a bicarinate structure. The first 3½

whorl A whorl ( or ) is an individual circle, oval, volution or equivalent in a whorled pattern, which consists of a spiral or multiple concentric objects (including circles, ovals and arcs). In nature File:Photograph and axial plane floral diagra ...

s form a slightly convex, conic embryonic shell. The initial whorl is smooth, while the second features curved vertical riblets. On the subsequent whorls, these riblets become irregular, often composed of two or more contiguous striae. The first post-embryonic whorl exhibits coarse wrinkles, minute thread-like striae, and faint traces of spiral cords. The surface gradually becomes more convex and develops an angular shoulder above the midpoint of the whorl, with the area below this shoulder nearly vertical. From the fifth whorl onward, the shell shows characteristics of maturity, with more rapid expansion. The angular shoulder transitions into a pronounced keel, and on the

body whorl The body whorl is part of the morphology (biology), morphology of the gastropod shell, shell in those gastropod mollusks that possess a coiled shell. The term is also sometimes used in a similar way to describe the shell of a cephalopod mollusk ...

, a second peripheral keel emerges, creating a concave space between the two. The base is convex, and the entire surface is intricately sculptured with spiral cords and striae. The coloration is a purplish-red-brown, darker toward the apex and the base, with a pale border below the suture extending to the apex. Yellow markings adorn the carinae, cords, and folds of the body whorl, adding contrast. 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 irregularly ovate and oblique, dark on the interior with a bluish-pearly luster. The outer

lip The lips are a horizontal pair of soft appendages attached to the jaws and are the most visible part of the mouth of many animals, including humans. Mammal lips are soft, movable and serve to facilitate the ingestion of food (e.g. sucklin ...

is smoothly arcuate, with minimal modification by the carinae. The

columella Lucius Junius Moderatus Columella (, Arabic: ) was a prominent Roman writer on agriculture in the Roman Empire. His in twelve volumes has been completely preserved and forms an important source on Roman agriculture and ancient Roman cuisin ...

is short, concave above, and obliquely truncate at the base. It is covered with a flesh-tinted callus and bears a very oblique, thin spiral lamella. The type specimen is a relatively thin shell, barely reaching full maturity. As the shell ages, it becomes notably thick and heavy. In gerontic (aged) specimens, the shell is exceptionally solid, with a thickened outer wall. The parietal wall is coated with a dense white callus, which bears a low, broad, conical prominence situated slightly within the aperture. The columella is heavily encrusted with white callus, and its spiral lamella is thick, blunt, and only faintly distinguished from the basal truncation of the columellar pillar. The type specimen is deceased and nearly entirely stripped of its thin yellow cuticle.

Distribution

This very rare species is

endemic Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...

Hawaii Hawaii ( ; ) is an island U.S. state, state of the United States, in the Pacific Ocean about southwest of the U.S. mainland. One of the two Non-contiguous United States, non-contiguous U.S. states (along with Alaska), it is the only sta ...

, occurring on

Kauai Kauai (), anglicized as Kauai ( or ), is one of the main Hawaiian Islands. It has an area of 562.3 square miles (1,456.4 km2), making it the fourth-largest of the islands and the 21st-largest island in the United States. Kauai lies 73 m ...

Island.

References

External links

* {{Taxonbar, from=Q131402555 knudsenii Gastropods described in 1895