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Polished Ammonites
Shark Remains
  Glossary of terms
To describe the specimens on this site as accurately as possible we have used some terms that are defined below.
Anterior   Towards the front.
aperture   Open end of the body chamber
Aragonite   A crystalline form of calcium carbonate.
Aristotole's Lantern   The five-sided feeding and locomotor structure sited around the mouth of sea urchins.
Articular Bones   The bones incorporated in the articulation between the skull and lower jaw in some vertebrates.
Axis   In trilobites, the ridge that runs from anterior to posterior, down the midline: in vertebrates, the first or second element of the backbone.
body chamber   The last-formed chamber which contained the body
Calyx   In crinoids, a cup-shaped structure to which the arms are attached; in plants, the outer circle of a flower made up of sepals.
Carapace   In crustaceans and chelicerates, the external shield covering head and trunk; in vertebrates, the upper shell.
Cartilage   Highly specialised tissue that is hard but flexible.
Cast   The filling of a mould.
Caudal Fin   The tail fin of a vertebrate.
Centrum (pl. Centra)   The main body of a vertebra.
Cephalon   The head of a trilobite.
Cephalothorax   The combined head and trunk region of an arthropod.
Cerci   The sensory appendages at the posterior of the abdomen of insects.
Chitin   A horny substance, forming all or part of the skeleton of arthropods.
Cirri   A tendril-like animal appendage; the jointed thoracic appendages of barnacles.
Denticle   A small, tooth-like structure.
Dentine   The bone-like substance that makes up the bulk of a tooth.
Dorsal   The upper surface or back.
Dorsal Fin   A midline, unpaired, vertical fin sited on the back of aquatic vertebrates.
Elytra   The modified anterior wings that act as protective covers for the membranous hindwings in beetles.
Evolute   Loosely coiled.
Exoskeleton   The hard outer casing of arthropods.
External Mould   An impression of the outside of an organism.
Glabella   In trilobites, the central region of the head; in vertebrates, the prominent front bone which joins the ridges above the eyes.
Internal Mould   An impression of the inside of an organism.
involute   Refers to a tightly coiled shell in which the inner whorls are largely concealed by the last whorl
Macroconch   The larger form of a shell in a species in which males and females differ.
Mandible   In vertebrates, the lower jaw, in invertebrates, the various mouth parts which hold or bite food.
Neural Arch   The upper portion of a vertbra.
operculum   The lid, horny or calcareous, which closes the aperture when the head and foot are withdrawn into the shell.
Pectoral Fin   One of a pair of forward-pointing fins on fish.
Phragmocone   In belemnites and other molluscs, the cone-like internal shell that is divided into chambers by speta and perforated by a siphuncle.
Pyrite   Gold coloured mineral composed of iron sulphide.
Sacral   Associated with the hip girdle.
Sclerotic Ring   A ring of bony plates around the eye socket in reptiles and birds.
Scute   The bony, scale-like structure found in reptiles.
Septum (pl.Septa)   A thin dividing wall.
suture   The spiral line along which all the whorls are contiguous
Thorax   In certain arthropods, the middle of the three main divisions of the body; in vertebrates, the chest region.
umbilicus   The cavity around the axis of coiling found in loosely coiled shells
Vertebra (pl vertebrae)   One bone in the series that makes up the backbone in vertebrates.
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