Volume 4

Monograph on the fossil Reptilia of the Wealden and Purbeck formations : supplement.

  • Richard Owen
Catalogue details

Licence: Public Domain Mark

Credit: Monograph on the fossil Reptilia of the Wealden and Purbeck formations : supplement. Source: Wellcome Collection.

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    A distal phalanx (ib., iv, 4), of the same character as that of the second toe, is longer in proportion to its breadth, and deeper ancono-thenally. The rough, obtuse termination is bounded below by a transverse groove indicative of an ungual callosity of a more definite form. The fifth metacarpal of the right fore-foot (PI, III, v, m, reversed) has been preserved. Its proximal surface is rather lozenge-shaped ; the transverse diameter is 2 inches 3 lines ; a circular, slightly concave, roughish articular surface is defined at the middle of the lozenge ; the rougher tuberosities, extending beyond it on each side, form the truncate angles of the lozenge in that direction; a smaller extent of rough surface defines, in a feebler degree, the angles in the opposite direction. The length of this metacarpal is 1 inch 7 lines; the breadth of the distal end is 1 inch 8 lines. The upper surface is smooth, broad, and almost flat. The radial surface is continued into the thenal one, which is strongly concave lengthwise, and these combined surfaces are roughened by longitudinal ridges and grooves. The ulnar surface slopes in that direction strongly from the upper one to meet the combined theno-radial surfaces; the distal articular surface is trapezoid in form, convex vertically, slightly concave transversely at its middle part, and continued upon a pair of tuberosities thenally; the toe which it supported would be directed obliquely to the ulnar side of the foot. The skeleton of the fore-paw of the Iguanodon, carpus inclusive, may be set down as about 16 inches in length, and about 11 inches in extreme breadth, showing a like dis- proportion of size to the hind-foot which the humerus does to the femur. In the Supplement,^ No. 1, to the ‘ Monograph on the Fossil Reptilia of the Wealden and Purbeck Formations,’ I remarked, in regard to its subject, “ the resemblance to the hind-foot of the Crocodilia in the suppression of the fifth toe, and the resemblance of the third and fourth toes, in regard to their nearly equal length, to those toes in the Monitor, render it most probable that the tridactyle foot of the Iguanodon, here described, is a ‘ hind-footbut it cannot be assumed that the fore-foot may not have been similarly modified.” We have now the desired evidence, and know that the fore-foot was pentadactyle, and that its chief speciality is in the stunted character of the terminal phalanges, at least of the second and third digits. The entire length of the bony framework of the fore-foot, without the carpus, is 1 foot 1 inch ; its breadth across the proximal ends of the meta- carpals is 9 inches: the length of the bony framework of the hind-foot, without the tarsus, is 1 foot 8 inches; its breadth across the proximal ends of the metatarsals is 9 inches. The fore-foot is smaller in proportion to the hind-foot in the Crocodile; it is still smaller in the Iguana. The length of the bony framework of the hind-foot in a Crocodilus hiporcatus, with a ’ Vol. of the Palseontographical Society, 4to, for 1858, p. 3.
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