Bostryx fragilis
Encyclopedia
Bostryx fragilis is a species
of tropical air-breathing land snail
, a pulmonate gastropod mollusk in the family Orthalicidae
.
The specific epithet fragilis is from the Latin language and means "fragile", it refers to the thin shell.
The type locality is Quebrada Santa Maria, 03°40’53’S 080°26’10’W, 25 m, Tumbes Region
, Peru.
, the tawny-brownish upper whorls
and the prominent last whorl.
The shell up to 18.9 mm in height, two times as long as wide, narrowly perforate, elongate, with hardly convex sides and fragile. Colour is whitish on a translucent background, the upper whorls are becoming gradually tawny-brown towards the apex
. The surface is slightly shining, the incrassate growth striae overlaid on the last whorls by whitish, low, axial costulae, which are partly forked and do not always cover the whole whorl, but may end in between the sutures or shell base. Upper whorls are with fine, interrupted spiral threads. Protoconch
is with wrinkles, mostly broken into granules and crossed by finely incised spiral lines. The shell has 6.8 whorls, that are hardly convex. The suture is slightly impressed. The aperture
is elongate-subovate, 1.61 times as long as wide, 0.40 times the total height. Peristome is thin and simple. Columellar margin is nearly straight, very narrowly dilated above.
The shell has 6.6-7.1 whorls. The width of the shell is 8.0-9.2 mm. The height of the shell is 16.9-18.9 mm. The width of the aperture is 4-5 mm. The height of the aperture is 6.6-8.2 mm. The height of the last whorl is 9.2-11.9 mm.
The holotype
has 6.8 whorls and dimensions of the holotype are as follows: The width of the shell is 8.7 mm. The height of the shell is 18.0 mm. The width of the aperture is 4.5 mm. The height of the aperture is 7.3 mm. The height of the last whorl is 11.3 mm.
Bostryx fragilis is closely allied to Bostryx juana (Cousin, 1887) from which it differs by (1) being smaller, (2) slightly more slender and (3) lacking the tawny-brown spiral bands. Bostryx fragilis further resembles Bostryx alausiensis (Cousin, 1887), also described from southern Ecuador. It differs by being (1) smaller, (2) stouter, and (3) having a larger aperture. Finally, it may be compared to Bostryx delicatulus (Philippi, 1867) from which it differs by (1) being stouter, (2) the brownish upper whorls and (3) the simple peristome.
There is a morphological resemblance between the species mentioned above and some Bulimulus
species occurring in the same region, e.g. Bulimulus inconspicuus
Haas, 1949, both in general shell shape and - superficially - also in protoconch sculpture
. The relationships and phylogeography
of these two genera in this region warrant further study.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of tropical air-breathing land snail
Land snail
A land snail is any of the many species of snail that live on land, as opposed to those that live in salt water and fresh water. Land snails are terrestrial gastropod mollusks that have shells, It is not always an easy matter to say which species are terrestrial, because some are more or less...
, a pulmonate gastropod mollusk in the family Orthalicidae
Orthalicidae
Orthalicidae are a family of tropical air-breathing land snails, terrestrial pulmonate gastropod mollusks are classified in the informal group Sigmurethra of the clade Stylommatophora...
.
The specific epithet fragilis is from the Latin language and means "fragile", it refers to the thin shell.
Distribution
The type locality is Quebrada Santa Maria, 03°40’53’S 080°26’10’W, 25 m, Tumbes Region
Tumbes Region
Tumbes is a coastal region in northwestern Peru and southwestern Ecuador. Due to the region's location near the Equator it has a warm climate, with beaches that are considered among the finest in Peru...
, Peru.
Description
Bostryx fragilis is characterized by the whitish lines on the thin, translucent shellGastropod 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...
, the tawny-brownish upper whorls
Whorl (mollusc)
A whorl is a single, complete 360° revolution or turn in the spiral growth of a mollusc shell. A spiral configuration of the shell is found in of numerous gastropods, but it is also found in shelled cephalopods including Nautilus, Spirula and the large extinct subclass of cephalopods known as the...
and the prominent last whorl.
The shell up to 18.9 mm in height, two times as long as wide, narrowly perforate, elongate, with hardly convex sides and fragile. Colour is whitish on a translucent background, the upper whorls are becoming gradually tawny-brown towards the apex
Apex (mollusc)
Apex is an anatomical term for the tip of the mollusc shell of a gastropod, scaphopod, or cephalopod mollusc.-Gastropods:The word "apex" is most often used to mean the tip of the spire of the shell of a gastropod...
. The surface is slightly shining, the incrassate growth striae overlaid on the last whorls by whitish, low, axial costulae, which are partly forked and do not always cover the whole whorl, but may end in between the sutures or shell base. Upper whorls are with fine, interrupted spiral threads. Protoconch
Protoconch
A protoconch is an embryonic or larval shell of some classes of molluscs, e.g., the initial chamber of an ammonite or the larval shell of a gastropod...
is with wrinkles, mostly broken into granules and crossed by finely incised spiral lines. The shell has 6.8 whorls, that are hardly convex. The suture is slightly impressed. The aperture
Aperture (mollusc)
The aperture is an opening in certain kinds of mollusc shells: it is the main opening of the shell, where part of the body of the animal emerges for locomotion, feeding, etc....
is elongate-subovate, 1.61 times as long as wide, 0.40 times the total height. Peristome is thin and simple. Columellar margin is nearly straight, very narrowly dilated above.
The shell has 6.6-7.1 whorls. The width of the shell is 8.0-9.2 mm. The height of the shell is 16.9-18.9 mm. The width of the aperture is 4-5 mm. The height of the aperture is 6.6-8.2 mm. The height of the last whorl is 9.2-11.9 mm.
The holotype
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
has 6.8 whorls and dimensions of the holotype are as follows: The width of the shell is 8.7 mm. The height of the shell is 18.0 mm. The width of the aperture is 4.5 mm. The height of the aperture is 7.3 mm. The height of the last whorl is 11.3 mm.
Bostryx fragilis is closely allied to Bostryx juana (Cousin, 1887) from which it differs by (1) being smaller, (2) slightly more slender and (3) lacking the tawny-brown spiral bands. Bostryx fragilis further resembles Bostryx alausiensis (Cousin, 1887), also described from southern Ecuador. It differs by being (1) smaller, (2) stouter, and (3) having a larger aperture. Finally, it may be compared to Bostryx delicatulus (Philippi, 1867) from which it differs by (1) being stouter, (2) the brownish upper whorls and (3) the simple peristome.
There is a morphological resemblance between the species mentioned above and some Bulimulus
Bulimulus
Bulimulus is a genus of small to medium-sized tropical or sub-tropical, air-breathing land snails, pulmonate gastropod mollusks in the subfamily Bulimulinae.-Shell description:...
species occurring in the same region, e.g. Bulimulus inconspicuus
Bulimulus inconspicuus
Bulimulus inconspicuus is a species of tropical air-breathing land snail, a pulmonate gastropod mollusk in the family Orthalicidae.- Description :Adult specimens of Bulimulus inconspicuus can measure up to 25 mm shell height...
Haas, 1949, both in general shell shape and - superficially - also in protoconch sculpture
Sculpture (mollusc)
The sculpture of a mollusc shell is the three-dimensional ornamentation on the outer surface, as distinct from the basic shape of the shell itself or colouration. Sculpture may be concave as well as convex. Sometimes it has microscopic detail. Sculpture refers to the calcareous outer layer, not the...
. The relationships and phylogeography
Phylogeography
Phylogeography is the study of the historical processes that may be responsible for the contemporary geographic distributions of individuals. This is accomplished by considering the geographic distribution of individuals in light of the patterns associated with a gene genealogy.This term was...
of these two genera in this region warrant further study.