Europe and the Middle East. In some
species, the size and indeed occur-
rence of nasal horns is quite variable;
individual specimens of B. gabonica
and B. latastei may lack horns
completely.
The Horned Puff Adder (Bitis
to the common name.
caudalis) from arid southwest Africa
also boasts a single spine-like scale
But these unusual structures are not
over each eye, whereas the Many-
unique to viperids. The small, rare and
horned Adder (B. cornuta) from the
little-known Northern Eyelash Boa
coast of southern Africa has tufts of
(Trachyboa boulengeri) is an inhabi-
two to seven supraorbital horns (each tant of the rainforests of Columbia
Supraorbital (or supraocular) horns, or comprising a single scale) that impart and Panama and also possesses
‘eyelashes’, have also become popular a rather malevolent, alien appearance. several enlarged supraorbital scales.
amongst viperids. The genus Cerastes
The tip of the tail is bright yellow,
consists of three species from the
Similarly, Mexican horned pitvipers
which is suggestive of caudal luring, a
deserts of North Africa and the
(Ophryacus spp.) have needle-like
behaviour also practiced by the
Middle East that are collectively
scales that project over the eyes. The Eyelash Viper.
referred to as horned vipers, although Black-tailed Horned Pitviper
only two of these taxons sport
(Mixcoatlus melanurus), also from
All of these facial projections consist
supraorbital appendages. The Desert Mexico, and the Sidewinder (Crotalus of single scales or amalgamations of
Horned Viper (Cerastes Cerastes) has cerastes), from the deserts of north-
scales, but what is their purpose?
a single pair of modified, spine-
like scales which can be conven-
‘The
has a pair of
iently folded back into a groove in
the postocular scale when the
spine-like scales which can be conveniently
snakes are travelling through nar-
row burrows or other tight spaces.
folded back into a groove when it is
The pronounced supraocular horns
of the Arabian Horned Viper (C.
travelling through tight spaces.’
gasperettii) may comprise a num-
ber of scales. Once again, consid-
erable plasticity is
western Mexico and the southwestern Confronted with a lack of tangible
exhibited as the horns are variable in USA likewise have supraorbital protu- evidence, some sources are quick to
size and individuals bereft of horns
berances. A native of Central and
seize upon a simple, vague and rather
are common; a single litter may con- South America, the Eyelash Viper
naive explanation. For example, it has
tain specimens both with and without (Bothriechis schlegelii) is a small
been widely suggested that these
horns. The false horned vipers
arboreal pit viper that is popular in
structures serve to break up the out-
(Pseudocerastes spp.) from the
collections, due no doubt to its
line of the snakes and thereby
Middle East and Asia derive their
extensive and strikingly beautiful
assist in camouflage. True, the species
collective common name from the
natural colour range, which includes
concerned are typically ambush
fact that supraorbital horns, where
brown, green, red, pink, yellow and
predators that rely upon crypsis to
present, are composed of a mass of
combinations thereof. An array of
remain undetected by potential prey
many small scales.
modified supraorbital scales gives rise items. However, the relatively small
Desert Horned Viper
Above: the Desert Horned Viper (Cerastes cerastes).
Image by Eric Isselee.