Page 15 - Shark

hook on head
dorsal spine for holding
Caudal fin female during
Spine on second mating
dorsal fin

Pectoral fin

anal fin
hyboduS
Relatives of this kind of shark Fossil of hybodus
appeared about 320 million years ago and
died out about 65 million years ago, along Pelvic fin
with the dinosaurs. hybodus appeared about
165 million years ago and grew to about 8 ft
(2.5 m) long. Males had claspers attached to back
their pelvic fins, as well as one or two hooks brush
on their heads to hold onto females during head
mating. hybodus also had an anal fin like pad
some modern sharks.

brush cut
Stethacanthus, at 3 ft (1 m) long, was a strange looking shark with a big
brush of denticles on its back and a pad of denticles on its head. The brush
may have been used in courtship. Alternatively, the two sets of denticles,
when opposing each other, could look like a big mouth and frighten off
attackers. Whatever ate Stethacanthus, which lived over 300 million years
ago, would have gotten a prickly mouthful.
great White JaWs
One of the largest sets of geat
white jaws in the world is
22 ½ in (57.5 cm) wide.
fin and head spines
Some ancient sharks had spines (left) in front
of their dorsal fins, which may have
protected them against large
predators. Males of some early
sharks had one or two hooks
(right) on their heads for
holding onto females while
Fin mating. Male chimeras Head
spine still have hooks on their spine Victorian
heads (pp. 6–7). boy, 40 in
(102 cm) tall
large,
round
eye
giant JaWs of a megalodon
A reconstruction of the jaws of a megalodon is shown
above, with the jaws of the great white inside them
to the same scale. There has been much speculation
as to the size of a megalodon’s jaws. Although an
early estimate put them at 9 ft (2.7 m) across, more
recent discoveries prove that a megalodon’s jaws
measured less than 6 ft (1.8 m) across, as shown
in this reconstruction from the Smithsonian
Institution in Washington, D.C. Megalodons are
only known from their teeth and vertebrae. They
This model of lived from 2–20 million years ago. Scientists
Triangular- Cladoselache has Mouth at still debate if the megalodon was an ancient
shaped, broad- seven gill slits, but end of snout, relative of the great white shark.
based pectoral fin it is now known to rather than
have had only five on underside
13