The Cambridge natural history, Vol. 08 (of 10)Gadow, Hans
Science
The Cambridge natural history, Vol. 08 (of 10)
Gadow, Hans
Animals
In the FORE-LIMB the humerus has a crest, stronger in the males than in the
females; it assumes extraordinary strength in some Cystignathidae, notably
in the male _Leptodactylus_. Radius and ulna are fused into one bone. The
carpalia are originally nine in number: radiale, ulnare, two centralia, and
five carpalia distalia, the fifth of which is reduced to a tiny nodule or
to a ligamentous vestige. The primitive condition still prevails in the
Discoglossidae. In most of the other Anura the fourth and third distal
carpalia, in any case very small, fuse with the enlarged ulnar centrale;
the radial centrale comes, in the Bufonidae and Pelobatidae, into contact
with the radius, so that the forearm articulates with three elements as in
the Urodela, but with this difference, that the intermedium of the Urodela
has been lost by the Anura. There are five metacarpalia and five fingers,
but the elements of the first or thumb are nearly vestigial, so that the
pollux is reduced to one or two nodules, scarcely visible externally. The
normal number of the phalanges of the second to fifth fingers is 2, 2, 3,
3. The distal phalanges are generally straight, either pointed or expanded
or with Y or T-shaped ends; but in the Hylidae, in _Hylambates_ amongst the
Ranidae, and in _Ceratohyla_, one of the Hemiphractinae, the terminal
phalanges are produced into curved claws which support the adhesive
finger-discs. There are, however, many genera of different families, which
possess finger-discs and have no claw-shaped {27}phalanges. The Hylidae,
and many of the climbing members of the Ranidae with adhesive discs,
possess an extra skeletal piece intercalated between the last and last but
one phalanges of the fingers and toes. This piece, a mere interarticular
cartilage in _Hyla_, is in the following Raninae developed into an
additional phalanx, so that their numbers are 3, 3, 4, 4 in the hand and 3,
3, 4, 5, 4 in the foot: _Cassina_, _Hylambates_, _Rappia_, _Megalixalus_,
_Rhacophorus_, _Chiromantis_, _Ixalus_, and _Nyctixalus_. All the other
Ranidae are without this additional phalanx, irrespective of the presence
or absence or size of digital expansions.[12]
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