Form and Function of Sharks 25
ment needed to chase down and feed on fast-swimming, warm-blooded
prey such as seals, sea lions, and tuna.
What kind of teeth do sharks have?
Shark teeth are usually depicted as triangular or slender pointed struc-
tures. Although this holds for many shark species, sharks and their rela-
tives possess an impressive diversity of tooth types, strongly influenced by
prey type. In addition, teeth in the upper and lower jaw may be different,
and tooth type changes with age and sex in some species (see “Do a shark’s
teeth change during its life?” below). Differences among species are great
enough that many shark species can be identified by their teeth alone.
Fish eaters tend to have long, slender teeth. Excellent examples of these
are makos (Isurus), Ragged Tooth / Sand Tiger Sharks, and squatinid angel
sharks. This is an ideal tooth form for grabbing slippery, evasive prey such
as fishes and squids, which are then often swallowed whole.
If a shark’s preferred prey is likely to be too large to swallow whole, then
holding and cutting equipment is needed. The easily identified notched
and serrated (saw-edged) teeth of a Tiger Shark accomplish this, and Tiger
Sharks have one of the most varied diets of any large shark species. Tiger
Shark teeth are often described as cockscomb-shaped because of their dis-
tinct uneven, notched shape and serrated edges, similar to the comb on the
head of a rooster. A Tiger Shark’s bite may be more effective because the
teeth in each side of both upper and lower jaws are mirror images of each
other. These opposing faces with a notch may increase the shearing action
of the teeth, especially when the shark swings its jaws from side to side as it
bites down on its prey.
Many sharks divide the labor of holding and cutting between their lower
and upper jaws. In carcharhinid sharks such as the Sandbar Shark, Car-
charhinus plumbeus, lower-jaw teeth are more slender and pointed, whereas
upper-jaw teeth are triangular with sharp serrations. As the shark’s mouth
is closed once or repeatedly, prey are impaled and held with the lower-jaw
teeth while the upper-jaw teeth work back and forth, cutting chunks of
flesh and severing bone. (Some squaliform sharks such as Kitefin Sharks,
Dalatias licha, reverse the functions and have sharper upper teeth.) Cut-
ting is aided by head and body shaking, twisting, and even spinning. White
Sharks, which take large pieces out of even larger prey such as whales, are
another species with different lower- and upper-jaw teeth, at least as adults.
Piranhas, another fish that bites chunks from its prey, have triangular teeth
that are remarkably similar in shape to those of many sharks.
Sharks that feed on unusual prey or in an unusual manner have un-