As the bones in the wing of the Pterodactyle thus agree in number and proportion with those in the fore foot of the Lizard, so do they differ entirely from the arrangement of the bones which form the expansors of the wing of the Bat.[1]
The total number of toes in the Pterodactyles is usually
four; the exterior, or little toe, being deficient; if we compare
the number and proportion of the joints in these four
toes with those of Lizards, (Pl. 22, F, G, H, I,) we find the
agreement as to number, to be not less perfect than it is in
the fingers; we have, in each case, two joints in the first,
or great toe, three in the second, four in the third, and five
in the fourth. As to proportion also, the penultimate joint
is always the longest, and the ante penultimate, or last but
two, the shortest; these relative proportions are also precisely
the same, as in the feet of Lizards.[2] The apparent
rostris, (Pl. 22, N, 44, 45,) the fifth finger was elongated to expand the wing, we should infer from the normal number of joints in the fifth finger of Lizards being only three, that this wing finger had but three joints. In the fossil itself the two first joints only are preserved, so that his conjectural addition of a fourth joint to the fifth finger, in the restored figure, (Pl. 22, A, 47,) seems inconsistent with the analogies, that pervade the structure of this, and of every other species of Pterodactyle, as described by Cuvier.
- ↑ The Bat, see Pl. 22, M, 30, 31, the first finger or thumb alone, is free, and applied to the purpose of suspension and creeping; the expansors of the wing are formed by the metacarpal bones, (26—29,) much elongated and terminated by the minute phalanges of the other four fingers, 32—45, thus presenting an adaptation of the hand of the mammalia to the purposes of flight, analogous to that which in the fossil world, the Pterodactyle affords with respect to the hand of Lizards.
- ↑ According to Goldfuss the P. Crassirostris had one more toe than Cuvier assigns to the other species of Pterodactyles; in this respect it is so far from violating the analogies we are considering, that it adds another approximation to the character of the living Lizards; we have seen that it also differs from the other Pterodactyles, in having the fifth, instead of the fourth finger elongated, to become the expansor of the wing.
It is however probable that the fifth toe had only three joints, for the
