A girdle is part of the anatomy of a chiton, one class of marine mollusks, the class Polyplacophora. The shell of a chiton consists of eight valves which articulate with one another. The girdle is a strong but flexible structure that in most cases encircles the plates, holding them all together.
Anatomy is the branch of biology concerned with the study of the structure of organisms and their parts. Anatomy is a branch of natural science which deals with the structural organization of living things. It is an old science, having its beginnings in prehistoric times. Anatomy is inherently tied to developmental biology, embryology, comparative anatomy, evolutionary biology, and phylogeny, as these are the processes by which anatomy is generated over immediate (embryology) and long (evolution) timescales. Anatomy and physiology, which study (respectively) the structure and function of organisms and their parts, make a natural pair of related disciplines, and they are often studied together. Human anatomy is one of the essential basic sciences that are applied in medicine.
Chitons are marine molluscs of varying size in the class Polyplacophora, formerly known as Amphineura. About 940 extant and 430 fossil species are recognized.
A mollusc valve is each articulating part of the shell of a mollusc. Each part is known as a valve or in the case of chitons, a "plate". Members of two classes of molluscs: the Bivalvia (clams) and the Polyplacophora (chitons) have valves.
Details of the external surface of the girdle are often useful in identifying the taxonomic family, genus and species of chiton. For example, the girdle may be covered in overlapping scales, spikes, or it may have tufts of glassy bristles protruding from it.
In biology, taxonomy is the science of defining and naming groups of biological organisms on the basis of shared characteristics. Organisms are grouped together into taxa and these groups are given a taxonomic rank; groups of a given rank can be aggregated to form a super-group of higher rank, thus creating a taxonomic hierarchy. The principal ranks in modern use are domain, kingdom, phylum, class, order, family, genus, and species. The Swedish botanist Carl Linnaeus is regarded as the father of taxonomy, as he developed a system known as Linnaean taxonomy for categorizing organisms and binomial nomenclature for naming organisms.
In a few genera of chitons, the girdle covers the valves either partially, as in the Black Katy chiton, or completely, as with the gumboot chiton.
The gumboot chiton also known as the giant western fiery chiton, is the largest of the chitons, growing to 36 cm (14 in) and over 2 kg (4.4 lb). It is found along the shores of the northern Pacific Ocean from Central California to Alaska, across the Aleutian Islands to the Kamchatka Peninsula and south to Japan. It inhabits the lower intertidal and subtidal zones of rocky coastlines.
