Glossary of terms used for Chondrichthyes (sharks, rays and chaemeras)

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• Abdominal ridges or keels. In some sharks, paired longitudinal dermal ridges that extend from the pectoral fins to the pelvic fins.
• Alar spines. Enlarged, hooked spines on the outer pectoral fins of adult male skates (family Rajidae).
• Amphitemperate. Referring to a species that occurs in temperate water in the northern and southern hemispheres, but absent from the tropics.
• Anal fin. A single fin on the ventral surface of the tail between the pelvic fins and caudal fin of some sharks and chimaeras, but absent in rays.
• Anus. In chimaeras, there is no cloaca, and solid wastes are separately discharged from the rectum through an anus, as in higher mammals.
• Barbels. Long conical paired dermal lobes on the snouts of sharks, that may serve to locate prey. Sawsharks have barbels in front of the nostrils, but most sharks with barbels have them associated with the nostrils.
• Batoid. A ray, a member of the superorder Batoidea: a sawfish, guitarfish, electric ray, skate, stingray, eagle ray, or devilray.
• Bicoastal. Off southern Africa, any cartilaginous fish that occurs off the northern west and east coasts, but does not occur off the southern or southwestern Cape.
• Bivalve. A group of mollusks (Class Bivalva) characterized by having two calcareous exoshells which are joined by a hinge which protects the soft-bodied animal inside. Includes clams, oysters, mussels, and their relatives.
• Body ridges. In sharks of the order Orectolobiformes, elongated longitudinal dermal ridges on the sides of the trunk and tail.
• Bony fish. Any member of the class Osteichthyes, with fins supported by jointed bony rays, the skeleton mostly of bone, and with prominent bony plates on the skull and usually flat bony scales.
• Caudal crest. In certain sharks, a prominent sawlike row of enlarged pointed denticles along the upper (and sometimes lower) edge of the caudal fin.
• Caudal filament. In chimaeras, the long, thin whiplike structure that extends behind the end of the caudal fin.
• Caudal fin. The fin on the end of the tail in sharks and chimaeras, lacking or converted into caudal finfolds in some species of rays.
• Caudal finfolds. In some whiptailed stingrays (family Dasyatidae), the dermal folds on the lower and upper surface of the tail, the remnants of the caudal fin.
• Caudal keels. In sharks and rays, a dermal keel on each side of the caudal peduncle that may extend onto the base of the caudal fin, and, may, in a few sharks, extend forward as a body keel to the side of the trunk.
• Caudal peduncle. That part of the precaudal tail extending from the dorsal and anal fins to the front of the caudal fin.
• Cephalopod. Member of a highly evolved, specialized group of mollusks (class Cephalopoda) including the cuttlefish, octopus, and squids.
• Cetacean. Any member of the Cetacea, a group of marine mammals including the whales, dolphins, and porpoises.
• Circumglobal. Occurring around the world.
• Circumtropical. Occuring around the tropical regions of the world.
• Claspers. The paired copulatory organs present on the pelvic fins of male cartilaginous fishes, for internal fertilization of eggs.
• Cloaca. The common chamber on sharks and rays through which body wastes and reproductive products pass, to be expelled to the outside through a common opening or vent.
• Crustacean. A member of the class Crustacea, a crab or shrimp- like organism with a hard chitonous exoskeleton and multiple jointed limbs. Includes lobsters, crabs, mole crabs, hermit crabs, shrimp, isopods, amphipods, the shrimplike mysids and euphausiids, and copepods.
• Cusp. The point of tip of a tooth or spine. Multicuspid refers to teeth with more than one cusp.
• Dermal denticle. A small tooth-like scale unique to cartilaginous fishes. Also known as a placoid scale.
• Disk, pectoral disk. In rays, the fused unit of head, snout, pectoral fins, and body.
• Dorsal fin. Located on the back between the head and caudal fin. All chimaeras and most sharks have two dorsal fins, while rays vary with two, one, or none.
• Egg-case. An envelope of flexible, horn-like protein that surrounds the eggs of cartilaginous fishes. In egg-laying species this is thick and protects the egg, much like the shell of a chicken's egg, but in live-bearers it is often soft and membranous, and disintegrates while the fetuses are developing.
• Elasmobranch. The shark-like fishes including the modern sharks and rays (neoselachians), but excluding the chimaeras.
• Endemic. A species or higher taxonomic group of organisms that is unique to a given area.
• Eye spots or ocelli. Large eye-like pigment spots located on the dorsal surface of the pectoral fins of some rays, possibly serving to frighten potential enemies.
• Fin spine. A large hard spine on the front edge of one or both dorsal fins of some sharks.
• Gastropod. Any snail or snail-like mollusk (Class Gastropoda).
• Gill slits. In sharks and rays, the row of openings on the sides or underside of the head for the discharge of water through the gills; in chimaeras these are covered by a soft GILL COVER, and water exits the gills through a single gill slit in front of the base of each pectoral fin.
• Head. That part of a cartilaginous fish from its snout tip to the last gill slit.
• Interdorsal ridge. A ridge of skin on the midback of sharks, in a line between the first and second dorsal fins; important in identifying grey sharks (Genus Carcharhinus).
• Intestinal valve. A dermal flap inside the intestine, often formed like a corkscrew or augur (spiral valve). In some sharks and rays the turns of the valve are very numerous and short (ring valve), and resemble a stack of washers, while in the requiem and hammerhead sharks the valve has uncoiled and resembles a bib or scroll (scroll valve).
• Invertebrate. Any animal which lacks a vertebral column.
• Labial furrows. Grooves around the mouth angles on many cartilaginous fishes, isolating erectile liplike labial folds that expand when the mouth is open.
• Mollusk. A group of invertebrates (phylum Mollusca) mostly distinguishable by the presence of a hard calcareous external shell. Includes the gastropods, bivalves, cephalopods, chitons, tooth shells, and other more obscure groups, some of which have lost or greatly reduced their shell.
• Nape or nuchal thorn. In skates (family Rajidae), a single prominent thorn on the midback, located just behind the spiracles and in between the paired shoulder or scapular thorns when present.
• Nasal flap. One of a set of dermal flaps associated with the nostrils, and serving to direct water into and out of them. The prominent Anterior nasal flaps are attached to the front of the nostrils and are sometimes expanded and fused with each other to form a nasal curtain. The posterior nasal flaps are low and associated with the rear, excurrent apertures of the nostrils.
• Nictitating lower eyelid. In the ground sharks (Order Carcharhiniformes), a movable lower eyelid which has special muscles that lift it and, in some species, completely close the eye.
• Oceanic. Referring to organisms inhabiting that part of the ocean beyond the continental and insular shelves, over the continental slopes, ocean floor, sea mounts and abyssal trenches. Also known as the pelagic zone or `blue water'.
• Papillae. Elongated fingerlike processes of skin, located around the spiracles of torpedo rays, and in the mouths and on the gills of some sharks and rays.
• Pectoral fins. A symmetrical pair of fore-fins, on each side of the trunk just in back of the head and in front of the abdomen. These are present in all cartilaginous fishes and correspond to the forelimbs of a four-footed land vertebrate (tetrapod).
• Pelagic. Referring to organisms that are free-swimming, not bottom-dwelling.
• Pelvic fin. A symmetrical pair of hind-fins on the sides of the body between the abdomen and precaudal tail which correspond to the hindlimbs of a four-footed land vertebrate (tetrapod).
• Placenta. An organ in the uterus of some ground sharks (Order Carcharhiniformes), formed of the embryonic yolk-sack and maternal uterine lining, through which maternal nutriment is passed to the embryo.
• Polychaete. Any member of a group (Class Polychaeta) of segmented marine worms, which usually have side bristles, belonging to the phylum Annelida.
• Pores, pigmented. In a few sharks and skates, the pores for the lateral line and ampullae of Lorenzini are conspicuously black- pigmented, and look like little black specks.
• Precaudal pit. A depression at the upper and sometimes lower origin of the caudal fin where it joins the caudal peduncle.
• Rear tips. The pectoral, pelvic, dorsal, and anal fins all have a movable rear corner or tip that is separated from the trunk or tail by a notch (inner margin). In some sharks the rear tips of some fins are very elongated.
• Rhomboidal. In the form of a rhombus or diamond.
• Rostrum. The cartilaginous structure that supports the snout.
• Saw or saw-snout. The elongated snout in sawfish and sawsharks, with side teeth formed from enlarged denticles, used to kill or dig for prey.
• Shelf. The area along the continents and islands between the shore-line and approximately 200 m depth.
• Slope. The bottom area from the edge of the outer shelf down to the ocean floor, below approximately 200 m.
• Snout. That part of a cartilaginous fish in front of its eyes and mouth.
• Snout filament. In smooth legskates (Anacanthobatidae), a tiny narrow threadlike process on the extreme front tip of the snout.
• Spiracle. A small opening between the eye and first gill slit of most sharks and rays, representing the modified gill slit between the jaws and hyoid (tongue) arch. This is secondarily lost in chimaeras and some sharks.
• Squalene. A long-chain oily hydrocarbon present in the liver oil of deepwater cartilaginous fishes. In some areas it is highly valued for industrial and medicinal use.
• Sting. A large, flattened spine with side barbs on the upper surfaces of the tails of most members of the stingray group (Myliobatoidei).
• Subcaudal keel. In a few dogfish sharks (family Squalidae), a single longitudinal dermal keel on the underside of the caudal peduncle.
• Subterminal mouth. Mouth located on the underside of the head, behind the snout.
• Subterminal notch. On the caudal fin of sharks, the abrupt notch on its lower margin that isolates the wedge-shaped terminal lobe from the rest of the fin.
• Tail. That part of a cartilaginous fish from the cloacal opening (vent) or anus to the tip of the caudal fin or caudal filament, and including the anal fin, second dorsal fin when present, and caudal fin.
• Temperate. Circumglobar northern and southern areas of moderate ocean temperatures usually ranging between 10o and 22o C.
• Tentaculum. Unique reproductive organs of adult male chimaeras. The frontal tentaculum is a curved, knob-ended organ with hooklike denticles located on the forehead. The paired prepelvic tentacula are platelike or complex structures with a row of hooked denticles in pockets just in front of the pelvic fins. Both are used by the male to hold the female during courtship and copulation.
• Terminal caudal lobe. In sharks, the free rear wedge-shaped lobe at the tip of the caudal fin, defined below by the subterminal caudal notch.
• Terminal mouth. Mouth located at the very front of the animal.
• Thorn. In skates and other rays, and a few sharks, enlarged, flat denticles with a sharp, erect crown.
• Tropical. Circumglobal band of warm coastal and oceanic water.
• Truncate. Blunt, abbreviated.
• Trunk. That part of a cartilaginous fish between its head and tail, including the abdomen, back, pectoral and pelvic fins, and often the first dorsal fin.
• Tubercles. Low conical processes of skin, located on the upper edges of the caudal fins of long-nosed chimaeras (Rhinochimaeridae).
• Uterine cannibalism. In mackerel sharks (order Lamniformes), a unique mode of reproduction in which the first fetuses deplete their yolk-sacks early, and subsist by eating eggs or smaller fetuses.

Text by Leonard J.V. Compagno, David A. Ebert and Malcolm J. Smale