Glossary of terms used for Chondrichthyes (sharks, rays and
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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
- 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
- Batoid. A ray, a member of the superorder Batoidea: a
eagle ray, or
- 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
- Body ridges. In sharks of the order
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 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
- 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
- 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
- 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
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
- 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
- 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
- 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
- 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
with side teeth formed from enlarged denticles, used to kill or dig for
- 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
- 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
- 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
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