Glossary of Shark Terms

Abyssal plain. Sea floor constituting vast expanses of deep ocean from 2000 to 6000 meters deep.

Alar thorns. Large, modified dermal denticles located near the pectoral apices of skates.

Ampullae of Lorenzini. Pores on the head that pick up electrical signals in the sharks environment.

Anal fin. Single fin located ventrally posterior to the pelvic fins. Not always present.

Anterior. Forward. Towards the snout.

Anterior margin. The leading edge of a fin.

Apex. (apices pl.) The free tip of a fin.

Apical Lobe. small protruding tip on the snout of a stingray

Aplacental yolksac viviparity. A mode of reproduction in which the young are primarily nourished by the yolk within their egg case rather than from a placental connection to the mother. Once the yolk is fully consumed the young are ready to pass through the birth canal. AKA Ovoviviparity.

Aplacental viviparity. A mode of reproduction in which the young are not nourished from a yolk sac placenta but are still contained within the uterus until ready to be live born.


Barbells. Paired sensory extensions (dermal lobes) that extend from the nasal areas of some sharks.

Bathypelagic zone. Oceanic area dropping beyond the continental shelves from about 1000 to 4000 meters deep. Above the continental rises and abyssal plain.

Batoid. A ray.

Benthic. Bottom dwelling.

Bivalve. A class of mollusk including mussels, clams, and oysters.

Branchial. Pertaining to the gills.

Branchial arches. Cartilage supporting the gills.

Breach. The action of launching completely or partially out of the water.

Buccal. Pertaining to the mouth.

Bycatch. In fishing the part of the catch taken incidentally. Usually discarded.


Calcified cartilage. Shark cartilage reinforced with the mineral hydroxyapatite to create stiffness as in bone.

Caudal fin. Tail fin.

Caudal keel. A ridge either side of the caudal fin base used for stability in some shark species.

Caudal spine. A long, thin, often serrated or barbed modified dermal denticle used as a defensive weapon by many rays.

Cephalic fins. The extensions on the sides of the mouths of Manta and Mobula rays used to funnel plankton into the mouth.

Cephalofoil. The lateral extensions of the head in Hammerhead sharks.

Chondrichthyes. A class of vertebrates including all cartilaginous fishes (sharks, rays, skates, and chimaeras).

Circumtemperate. Occurring around the world in temperate water.

Circumtropical. Occurring in all the tropical seas around the world.

Claspers. Paired extensions of the pelvic fins in males, adapted for insertion into the female’s cloaca during copulation. See also Tenaculum.

Cloaca. Ventral cavity into which the urinary, intestinal, and reproductive tracts enter.

Crepuscular. Most active at dawn and at dusk.

Crura. Special lobes on the pectoral fins of skates that help it walk along the bottom.


Demersal. Living on or near the bottom.

Denticle band. A patch of denticles found dorsally on the discs of many stingrays. The position and extent changes by species and growth stage.

Denticles. Tiny tooth-like plates that create a protective and abrasive surface on the skin.

Dermal. of the skin.

Disc. The pectoral fins, torso, and head of a ray or skate.

Diurnal. Most active during the day.

Dorsum. Back or upper part of a shark or ray’s torso or disc.


Elasmobranch. Subclass of the class Chondrichthyes that includes all shark and ray species.

Embryophagy. Where the smaller siblings are consumed by the largest embryos during development. Only recorded in Sandtiger sharks.

Euryhaline. Able to tolerate both fresh and salt water.


Falcate. Sickle shaped.

Fin spine. A modified denticle adapted into a defensive weapon extending from the leading edge of the dorsal fins in some sharks.

Finfold. A long thin flap of skin on the tails of upper and lower midline of many stingrays. Dorsal finfold / Ventral finfold.

First dorsal fin. Located dorsally posterior to the head. The classically recognizable shark fin.


Heterocercal tail. Tail lobes of uneven lengths.

Homeothermy. A type of thermoregulation in which the body temperature always remains constant.


Infaunal. Living in the sediment or sand under the seafloor.

Interdorsal ridge. A raised ridge of skin between the first and second dorsal fins.


Labial furrows. Grooves on either side of the mouth.

Lateral line. A canal running along either side of the body of a shark that is sensitive to vibrations.

Lower caudal lobe. Referring to the lower half of the tail (sometimes vestigial).


Malar thorns. Large, modified dermal denticles located midway along the anterior margins of skate pectoral fins.

Matrotrophy. A mode of embryo development in which the source of nourishment is not limited to the yolk, but is supplemented by nourishment derived from the mother.


Nasal curtain. A fleshy flap partly covering the nostrils of skates and Myliobatid rays.

Nictitating membrane. A lower moveable eyelid that can be raised to protect the eye.

Nocturnal. Most active at night.

Nuchal thorns. Large, modified dermal denticles located along the centre-line of rays and skates.


Ocelli. Fake eye spots (usually on the pectoral fins) formed by circular dark spots or rings, sometimes with a white centre. Used to scare other predators.

Oophagy. A process by which infertile eggs are released into the oviduct to nourish the existing embryos.

Oral papillae. Small fleshy structures on the floor of some ray’s mouths.

Osmosis. The chemical process in which water is attracted to an area with a higher salt content.

Oviparity. A mode of reproduction in which the embryo is ‘laid’ in an egg case that is expelled via the cloaca and left to develop attached to the reef or sea floor.

Ovoviviparity. A mode of reproduction in which the embryo is contained within a membranous egg case. Upon hatching the young shark remains within the oviduct until fully developed. A placenta is not formed.


Parabolic. Broadly conical with a rounded tip. Parabolic rostral lobe = U-shaped snout.

Pectoral fins. Paired fins located ventrally posterior to the head in sharks. And forming the disc in rays.

Pelvic fins. Paired fins located posterior to the Pectoral fins.

Posterior. Pertaining to the rear of the body.

Precaudal pit. An indentation in front of the caudal fin.


Rectal gland. Gland in the intestine responsible for the collection of excess sodium chloride (salt). The salt is directed to the gut for expulsion.

Rete mirabile. The lattice of heat exchanging blood vessels that aid in thermoregulation.

Rhomboidal. Kite shaped or diamond shaped. Referring to the shape of a ray.

Rostrum. Snout.

Rostral ridges. Ridges running longitudinally along the snout.


Scapular thorns. Large, modified dermal denticles located at the shoulder region of skates.

Seamount. A peak rising from the seafloor that does not break the surface.

Second dorsal fin. Located posterior to the First dorsal. Often smaller than the first.

Spiracle. An opening on each side of the head used in respiration.

Subrostral lobes. The fleshy ridges under the snouts of cownose and eagle rays.

Supraorbital ridge. A hard ridge above each eye.

Sympatric. Sharing the same range.


Tapetum lucidum. A mechanism behind the retina that reflects light back increasing the intensity of the image.


Tenaculum. Head Clasper present on male Holocephalans, used to grasp the female during copulation.

Thermoregulation. The ability to control body temperature. Specifically in sharks the ability to maintain a core temperature higher than the surrounding water.

Thornlets. Tiny thorns that are barely larger than a regular denticle.

Trophodermic nutrition. A method of feeding viviparous embryos wherein nutrition (uterine milk) is secreted through the uterine epithelium that is not in direct contact with foetal tissue.

Tropical. Above 18ºC/64ºF.

Tubercles. Soft or hard projections on the surface of the skin.


Upper caudal lobe. Referring to the upper half of the tail.

Uterine Canibalism. See Embryophagy.


Ventrum. The belly or underside of a shark or ray’s torso or disc.

Viviparity. A mode of reproduction in which the embryos initially feed on uterine milk secreted from the uterus and nutrients from the yolk sac. Eventually a placental structure develops between the yolk sac and the Uterine wall.