Notes on Mesozoic vertebrate fossils / by O.C. Marsh.

  • Othniel Charles Marsh
Date:
1892
Catalogue details

Licence: Public Domain Mark

Credit: Notes on Mesozoic vertebrate fossils / by O.C. Marsh. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    The fore liml)s are unnsniilly sinall in comparison with tlie posterior, and tlie relative size of tlie two is shown on Plate 11. The scapular arch presents many points of interest. The scapula is large, and so much curved that the axis of its shaft is nearly pai-allel to the ai-ticular faces of its lowei extremity, (Plate II, figure 1, s). On the anterior margin, above the articulation for the coracoid, 'is a strong protuIterance, with a well-defined facet, adapted to the support of the clavicle, if such a bone were present. The coracoid is very small, and is perforated by a large foramen (Plate II, figure 1, c). The two peculiar bones now generally regarded as belonging to the sternum were separate, as shown in Plate III, figure 1. The humerus is comparatively short, and has a prominent radial crest. The radius and ulna are much elongated, the latter being longer than the humerus, and the radius about the same length. The ulna has a prominent olecranon process, and is a stouter bone than the radius. The carpal bones were quite short, and appear to have been only imperfectly ossified. The fore foot, or manus, was very long, and contained three functional digits only. The first digit was rudimentary, the second and tliird were nearly equal in length, the fourth was shorter and less developed, and the fifth entirely wanting, as shown in Plate IT, figure 1. In the functional digits (II, III, IV), the phalanges are elongate, thus materially lengthening the fore foot. The ter- minal phalanges of these digits are broad and flat, showing that they were covered with hoofs, and not w^ith claws. The limb as a whole was thus adapted to locomotion or support, and not at all for pi-ehension, altliough this might have been expected from its small size and position. The elongation of the fore-arm and manus is a peculiar feature, especially when taken in connection with the ungulate phalanges. It may, perhaps, be explained by supposing that the anmial gradually assumed a more erect position until it became essentially a biped, while the fore limbs retained in a measure their primitive function, and did not become prelien- sile, which was'the case in some allied forms. The pelvis is shown in Plate II, figures 2 and 3, and has already been described by the writer. Its most notable features are seen in the i)ubis and ischium, the former having a very large expanded prepul)is, with the postpubis rudimentary^ wlnle the shaft of the ischium is greatly elongated. The femur is long, and the shaft nearly straight. The great trochanter is well developed, while the third trochanter is large and near the middle of the shaft, as shown in Plate II, figure 2. The external condyle of the distal end is projected well backward, indicating great freedom of motion at the knee.
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