Whaler Sharks - seafdec.org.my

26 S h a r k s a n d R a y s o f B o r n e o
dorsally and well inward from disc margin
(fig. 21) ............................................ 13
Anterior part of head extending forward
beyond disc (fig. 22); eyes located laterally
on side of head (fig. 22) ...................... 15
13. Disc very broad, width more than 1.5
times length (fig. 23); tail very short and
filamentous (fig. 23) ..............................
...... Family Gymnuridae, Butterfly Rays
fig. 23; 238
Disc narrower, width less than 1.5 times
length; tail much longer and thicker ....
........................................................ 14
14. Caudal fin present (fig. 24); no thorns or
tubercles on disc or tail .........................
... Family Plesiobatidae, Giant Stingarees
fig. 24; 180
Caudal fin absent; central disc and dorsal
surface of tail normally with some
thorns or tubercles .................................
................... Family Dasyatidae, Stingrays
a. No skin folds on tail; base of tail narrow
and typically rounded to slightly
compressed in cross-section (fig. 25) ..... b
Skin folds present on undersurface of
tail, and sometimes on dorsal surface
after sting; base of tail relatively broad,
distinctly depressed (fig. 26) .................. c
b. No stinging spine; many long, sharp
thorns over entire disc ............ Urogymnus
fig. 27; 236
One or more stinging spines on tail
(if lost, scar visible); no long, sharp
thorns present over sides of disc
(sometimes with low thorns near
midline of disc) .................... Himantura
fig. 28; 190
fig. 21 fig. 22
fig. 23
fig. 24
fig. 25 fig. 26
fig. 27
fig. 28
c. Disc oval or subcircular; ventral skin fold
tall, extending to tail tip ..................... d