Introducing Sharks, Skates, Rays, and Chimaeras 17
smallest skates, the pygmy skates, are in the genus Fenestraja; they reach
total lengths of 20 to 30 cm (8–12 in).
Chimaeras are more modest in size, with an adult length of 40 to 150
cm (1.3–4.9 ft); females are often larger than males, but not in all species.
The largest chimaeras are Carpenter’s Chimaera (Chimaera lignaria) from
New Zealand and the Rabbit Fish (Chimaera monstrosa) from the eastern
Atlantic. At the shorter end of the range is the 40-cm (16-in) Striped Rab-
bitfish, Hydrolagus matallanasi, from coastal Brazil.
These size comparisons highlight an interesting fact about variation
among selachian families. Large (or small) size is not necessarily a fam-
ily trait. The somniosidae sleeper sharks and dalatiidae kitefin sharks are
two very closely related squaliform families, so close that some taxono-
mists consider all of them in one family, the Dalatiidae. This group in-
cludes sharks that fall into several extreme categories. Two dalatiids are
among the smallest sharks known, at 22 to 25 cm (9–11 in) long, whereas
the somniosid sleeper sharks are among the largest, reportedly 7.3 to 7.6
m (24–25 ft) long. One of these, the Greenland Shark, holds the record
for farthest-northern-occurring shark, being captured along the northern
coast of Greenland, above 83° north. (The North Pole is at 90° north, or
only about 400 miles north of northern Greenland.) The Portuguese Dog-
fish is a somniosid and is the deepest-living shark known.
Finally, and to the disappointment of 14-year-old boys everywhere, the
biggest sharks are usually female.
What is the fastest shark?
Selachian true sharks on the whole are slow swimmers. Their form of
swimming, which involves passing S-waves down the body from head to
tail, limits their speed compared to that of bony fishes (see “How do sharks
swim?” in chapter 2). The fastest bony fishes are tunas and their relatives.
Tunas swim by quick side-to-side beating of the tail. The fastest sharks do
the same and are aptly named mackerel sharks because of this convergent
swimming motion. The fastest shark is the Shortfin Mako, Isurus oxyrin-
chus. Makos have been clocked at speeds of 32 kph (20 mph). This may
not sound impressive, which may be why you will find erroneous swim-
ming speeds on websites ranging as high as 95 kph, or 59 mph. Nothing—
manmade or otherwise—goes that fast underwater for very long. Nuclear
submarines top out at 46 kph, or 29 mph. Remember: a shark only has to
swim as fast as or slightly faster than its prey, for a short period. A study of
swimming in Yellowfin Tuna (Thunnus albacares), one of the mako’s favorite
foods, showed average burst speeds of 24 mph, with a range of values for
the four fish studied of between 11 and 46 mph. The mako doesn’t have