Bones of the Extremities. Ligns. [225] and [226].—The thigh-bone (femur), both bones of the leg (tibia and fibula), and many of the metatarsal and phalangeal bones have been discovered; the osteology of the hinder extremity is, therefore, almost perfect. The thigh-bone ([Lign. 225]; and Petrif. p. 292,) is of a very remarkable character, having a closer resemblance to the femur of a huge mammalian, than to that of a reptile.[647] Several perfect specimens have been discovered, as well as the associated bones of the leg (Petrif. p. 293, Lign. 62); but the first fragment that came under my notice, was the middle portion of the shaft of a femur of enormous size, and of an irregular quadrangular form; and so shapeless and unintelligible it then appeared, that several years elapsed before its real nature was determined. (Foss. Tilg. For. pl. xviii.)
[647] See Cuvier’s Ossem. Foss. vol. ii. p. 36.
Lign. 225. Left Femur of the Iguanodon. 1/10 nat. size.
Anterior aspect.
Wealden. Brook Bay, Isle of Wight.
| a. Outer trochanter. b. Median trochanter. c. Inner condyle. d. Outer condyle. e. Anterior infra-condyloid fissure. f. Head of the femur. |
An entire thigh-bone of an adult Iguanodon, from the Weald clay in the west of Sussex, measured three feet eight inches in length.[648] end thirty-five inches in circumference at the condyles; and I have a femur of a very young animal, that is but five inches long. The form of the thigh-bone is so peculiar, that fragments may easily be recognised. The head of the femur ([Lign. 225], f,) is hemispherical, and projects inwards; there is no appearance of a ligamentum teres; a flattened process or trochanter ([Lign. 225], a,) forms the external boundary of the neck of the bone, from which it is separated by a deep and narrow vertical fissure; the shaft is of a sub-quadrangular shape, and a slightly elevated ridge, produced by the union of two broad, flat, longitudinal surfaces, extends down the middle of the anterior face, and, diverging towards the inner condyle, gradually disappears. The bone terminates below in two large condyles, separated in front and behind by a deep, narrow cleft, or groove ([Lign. 225], e). Near the middle of the inner edge of the shaft, there is a compressed ridge, with an angular projection, or trochanter. Thus the upper part of the femur maybe known by the presence of the flattened, or laterally compressed trochanter; and if that process be wanting, a fractured surface indicating its position may be detected; the middle of the shaft is characterized by its broad angular faces, and the inner submedian trochanter: the condyloid or inferior extremity of the bone may be distinguished by the deep groove between the condyles, both in front and behind.
[648] The average length of the adult femur is estimated at about four feet five inches.