|
Raphitoma Columnae
''Raphitoma columnae'' is an extinct species of sea snail, a marine gastropod mollusk in the family (biology), family Raphitomidae. Description The length of the shell reaches 23 mm, its diameter 7 mm. Compared with ''Raphitoma harpula'', the shell is longer, the Whorl (mollusc), whorls are less convex, the suture is less impressed. The body whorl is shorter and less depressed on top. The axial ribs are hardly oblique. The transverse striae are uniform and don't form nodules when crossing the ribs. The siphonal canal is straight, shorter and hardly noticed. < ...
|
Species
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. 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. Other ways of defining species include their karyotype, DNA sequence, morphology, behaviour or ecological niche. In addition, paleontologists use the concept of the chronospecies since fossil reproduction cannot be examined. The most recent rigorous estimate for the total number of species of eukaryotes is between 8 and 8.7 million. However, only about 14% of these had been described by 2011. All species (except viruses) are given a two-part name, a "binomial". The first part of a binomial is the genus to which the species belongs. The second part is called the specific name or the specific epithet (in botanical nomenclature, also sometimes i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
