''Comitas crenularoides'' is an extinct
species of
sea snail
Sea snail is a common name for slow-moving marine gastropod molluscs, usually with visible external shells, such as whelk or abalone. They share the taxonomic class Gastropoda with slugs, which are distinguished from snails primarily by the ...
, a
marine
Marine is an adjective meaning of or pertaining to the sea or ocean.
Marine or marines may refer to:
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gastropod
The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda ().
This class comprises snails and slugs from saltwater, from freshwater, and from land. T ...
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 ...
in the
family Pseudomelatomidae
Pseudomelatomidae is a family of predatory sea snails, marine gastropods included in the superfamily Conoidea (previously Conacea) and part of the Neogastropoda ( Bouchet & Rocroi, 2005).
In 1995 Kantor elevated the subfamily Pseudomelatomina ...
, the turrids and allies.
Description
The length of the shell attains 24 mm (without embryonic whorls), its diameter 8 mm.
(Original description) The shell is moderately large and narrow-elongate. The
spire is many-whorled and longer than the
aperture and the
siphonal canal
The siphonal canal is an anatomical feature of the shells of certain groups of sea snails within the clade Neogastropoda. Some sea marine gastropods have a soft tubular anterior extension of the mantle called a siphon through which water is ...
. The
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).
Whorls in nature
File:Photograph and axial plane floral ...
s are nodulosely costate, with a rather well marked subsutural concavity. The sinus in this region is well-defined, moderately broad and deep. The siphonal canal is rather short and straight. The apical angle is about twenty-five degrees. The embryonic whorls of the holotype are unfortunately missing. The spire consists of about eight convex whorls with the greatest convexity about the middle of each whorl. The posterior third of each whorl is rather deeply concave immediately under the suture, which gives the appearance to this part of the shell of rather a strong overlap of the whorls, anterior two-thirds convex, most marked at the ribs. The aperture is oval, somewhat contracted posteriorly, and gradually drawn out anteriorly into a short, slightly curved and open siphonal canal, which is about the same length as the aperture. The outer
lip is thin and slightly crenulated at the outer edge with a very distinct, broad and deep sinus just below the rather prominent subsutural band and situated in the concave posterior third. The sinus is about half as deep again as broad, thence the outer lip projects prominently forward, then gently arched to join the anterior canal. The
columella is simple, slightly bent and tapering. The posterior whorls are ornamented with slightly oblique ribs, developed in the anterior two-thirds of the whorls and extending right up, though gradually fading, to the anterior suture, thus leaving the posterior third practically free from costulate elevations. On the anterior whorls the ribs fade sooner towards
the anterior suture, though strongly elevated and prominent medially, giving rise to the appearance rather of a medial band of nodules or tubercles than to fully developed ribs. The ribs or tubercles number about nine to a whorl. Spiral ornament consists of four or five strong spiral threads in the anterior two thirds of each whorl, while the
body whorl
The body whorl is part of the morphology of the 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.
In gastropods
In gastropods, the b ...
shows about eight or nine, and one strong thread just adjacent to the posterior suture, making rather a prominent and characteristic subsutural band. On the posterior whorls the anterior group of threads are comparatively broad, with narrower grooves between, but anteriorly the grooves widen out till on the penultimate whorl the grooves or interspaces are broader than the threads, and become still more distinctly so on the body whorl. As the grooves widen out much finer spiral threads become visible in this space, the interspaces on the body whorl showing three of these finer intercalated threads. In the concave space between the subsutural band and the threads of the anterior portion of the whorl, which is occupied by the growth lines of the sinus, there are two or three
fine spiral threads, with still finer threads, just visible under a lens, on either side of them. The ribs and spiral ornament are both traversed by fine and close lines of growth, which by their marked sinuation and forward curvature clearly indicate the nature and position of the shell.
Pritchard, G. B. ,"A Revision of the Fossil Fauna of the Table Cape Beds." Proceedings of the Royal Society of Victoria v. 8 (1896)
Distribution
This marine species is endemic to Australia
Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...
. Fossils have been found in Eocene strata of Table Cape, Tasmania
References
External links
*
{{Taxonbar, from=Q55608084
crenularoides
Gastropods described in 1896
Gastropods of Australia