ORDER: Anura
("An-"
without, "ura" tail; from Greek)
Frogs & toads
Left: Mantella
aurantiaca from Madagascar.
Definition: Amphibians that possess
enlarged legs with specialized ankle structure, a fused hip (termed a urostyle),
and lack a tail in the adult stage. All anurans possess four
well-developed limbs as adults. The hind limbs are larger, sometimes
greatly so, than the forelimbs, and are used in hopping or jumping.
Unlike other terrestrial vertebrates, frogs and toads have four (vs.
three) joints in the hindleg. Most have some trace of an external ear opening, covered by a large
tympanic membrane (ear drum), and most males have a true voice.
"Painted
reed frog," from the African family Hyperoliidae.
Painting ©1999 Carel P. Brest Van Kempen.
This is a truly diverse group. With
the increased exploration of tropical regions during the late 20th
century, the number of known frog species easily doubled. There are
now as many described frogs and toads as mammals, and the number grows
annually.
Overview: Frogs
and toads represent the overwhelming majority of living amphibians,
with nearly 3,800 recognized species. The greatest diversity within
the assemblage is probably found in the Bufonoidea, a group that
includes true toads (Bufonidae), tree frogs (Hylidae and
Rhacophoridae), poison dart frogs (Dendrobatidae), and others. Species
in the Bufonoidea include burrowers, climbers, and swimmers. At the
other extreme is the Microhyloidea, containing small-mouthed burrowing
toads.
Burrowing frogs show considerable
diversification. Burrowers tend to have robust skulls with less of a
neck than in other frogs and the hind limbs are fairly short. Genera
such as Breviceps and Notaden have virtually no
protuberant snout, while Scaphiopus and Rhinophrynus
have a digging cuticle on the hind soles. When preparing to burrow,
these amphibians greatly distend the body to hold a large quantity of
water.
Similar in form are South America's
"mobile-mouth" horned frogs (Ceratophrys), stout
burrowers with enormous mouths. Horned frogs do not generally engage
in water-hoarding burrowing, living in very moist forests. Their large
body allows capture of large prey, including small mammals, birds,
lizards, snakes, and other frogs.
Tree frogs represent several
families of highly variable body types. Included are bizarre casque-headed
frogs (Corythomantis), flying frogs (Rhacophorus),
toad-like frogs (Gastrotheca), and graceful tree frogs (Hyla).
Some species may spend their entire lives in a single bromeliad plant,
while others will inhabit any available pond or puddle of water.
Click on names for species accounts:
Green
& Black poison dart frog
White's
tree frog
Pacific
tree frog
Golden
mantella
Literature:
Duellman,
Wm., and Linda Trueb. 1986. Biology of amphibians. McGraw-Hill.
Hofricher,
Robert (editor). 2000. Amphibians: the world of frogs, toads,
salamanders and newts. Firefly Books.
Zug,
George. 1993. Herpetology, an introductory biology of
amphibians and reptiles. Academic Press, San Diego.
