Abdominal ridges. Paired dermal ridges running from the pectoral fin base to the pectoral fin base.

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

Alar thorns. Large, modified dermal denticles on the wings of adult male 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.

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) around the mouth 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.

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.


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

Dermal. of the skin.

Diurnal. Most active during the day.

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


Elasmobranch. Subclass or the class Chondrichthyes. 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 some sharks dorsal fins.

Finfold. A long thin flap of skin in the tails of most 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 temp. 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).


Nictating membrane. A lower moveable eyelid.

Nocturnal. Most active at night.


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

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.


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.

Rostrum. snout.

Rostral ridges. Ridges running longitudinally along the snout.


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.


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.