Elements of the comparative anatomy Elements of the comparative anatomy of vertebrates elementsofcompar00wied Year: 1886 LIMBS. 107 other points the humerus, radius, and ulna correspond closely with those of existing Birds. There was only one carpal (radiale), and the manus consisted of three free metacarpals and digits, of which the first possessed two, the second three, and the third four phalanges : all the digits were provided with claws (Fig. 92). Ten families of existing Carinate Birds possess the same number (two) of phalanges on the first finger as Archieopteryx, the distal one bearin
Elements of the comparative anatomy Elements of the comparative anatomy of vertebrates elementsofcompar00wied Year: 1886 LIMBS. 107 other points the humerus, radius, and ulna correspond closely with those of existing Birds. There was only one carpal (radiale), and the manus consisted of three free metacarpals and digits, of which the first possessed two, the second three, and the third four phalanges : all the digits were provided with claws (Fig. 92). Ten families of existing Carinate Birds possess the same number (two) of phalanges on the first finger as Archieopteryx, the distal one bearing a claw. Four families of Carinatse also possess three phalanges on the second finger, like Archreopteryx, but in only two of these families is there a claw on this digit. The third finger in all existing Carinates has only one phalanx,1 as compared with four in Archfeopteryx, and this never bears a claw. Amongst the Ratitoe, Apteryx and Casuarius possess only a single digit (the second), and it, like the first finger of Struthio and Khea, is provided with a claw. The strongly-developed and pneumatic2 bones of the arm and fore-arm stand out in sharp contrast with the greatly reduced skeleton of the manus; and the anterior extremities in most Birds of flight, as the principal organs of locomotion, greatly exceed the posterior in size (Fig. 93, ff, Ji., U\ FIG. 93.—ANTERIOR EXTREMITY OF BLACKBIRD (Turdux merula). H, humerus ; R, radius ; U, ulna ; r, radiale ; u, ulnare ; Me, Me, the three meta- carpals, with which the distal row of carpals has united ; / to ///, the three digits. *&' The tarsus of Birds consists in the embryo of three elements, two small proximal and a broader distal. The former (tibiale and fibulare) unite later with the distal end of the tibia, thus forming a tibio-tarsus, while the latter, which corresponds to tarsalia 1 to V, becomes included in the base of the metatarsus. Thus the foot of adult Birds no longer possesses any distinct tarsal elements, t
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