On parts of the skeleton of a mammal from Triassic rocks of Klipfontein, Fraserberg, South Africa (Theriodesmus phylarchus, Seeley), illustrating the reptilian inheritance in the mammalian hand / by H.G. Seeley.

  • Seeley, H. G. (Harry Govier), 1839-1909.
Date:
1888
Catalogue details

Licence: Public Domain Mark

Credit: On parts of the skeleton of a mammal from Triassic rocks of Klipfontein, Fraserberg, South Africa (Theriodesmus phylarchus, Seeley), illustrating the reptilian inheritance in the mammalian hand / by H.G. Seeley. 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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    compared with that of Amphibians and Reptiles. Dr. R. Wiedersheim, in a paper* on the central bones in the carpus and tarsus in the Axolotl, shows some remarkable conditions of the carpus to be developed with age. There are at first three bones in the proximal row, and four bones in the distal row, though ultimately the latter series numbers fivet on the left side of the body. Between these rows is the centrale, at first single, and ultimately represented by two cartilages on one side and three on the other. I should desire to see preparations before affirming that a linear series of three central elements is a normal characteristic of the Axolotl, but this number appears probably to be present. The presence of two central bones in certain Reptilia is much better established. Dr. Franz Bayer has figured and described | two central elements in the young Hatteria which have a linear arrange- ment, and are placed above the second and third tarsals of the distal row. And this condition appears to have been observed independently by Dr. G. Baur and by M. L. Dollo. It is among Chelonians, however, that the two centralia are most strikingly developed in linear arrangement towards the radial side. But, though the condition of the carpus in this fossil is thus shown to be Amphibian and Reptilian, it is typically Mammalian in all points except that of the central bones. But no Mammal shows more than one central bone, and the number of types in which that one is persistent throughout life is not large. Dr. G, Baur, indeed, affirms § that a centrale has been shown to occur at some period of life in all orders of Mammals except Ungulata and Cetacea, but figures and detailed descriptions have yet to be given to demonstrate the proposition for some orders. Perhaps the carpus of Cheiromys nearly parallels Theriodesmus, except that in the Lemur the scaphoid and lunar bones are not united. The one large centrale is in contact proximally with the scaphoid and lunar, and it meets all the bones of the distal row. The bone is relatively smaller in the Orang-utang, but the structure is the same. Yrolik remarks || that this bone is found in the Gibbons, and appears to exist in all the lower Monkeys. Yrolik also figures (loc. cit., p. 204) a second ossification between the trapezium and scaphoid, regarded by him aS a sesamoid bone for the tendon of the adductor longus pollicis. Baur {Jog. cit.) states that he has evidence of the centrale in Man, the Cat, and Dog. In the embryo of Lutra the centra,] bone was quite free and very fully developed, ’while the radiale arjd intermedium [= scapho-lunar] were coalesced. Hyrax capensis has a free centrale, though it is only free in this species of the genus. The presence of this bone cannot but mark an ancient connection between the orders in which it is found ; just as the two or three central bones of * “ fiber die Yermehrung des Os central© in Carpus und Tarsus des Axolotls,” von R. Wiedersheim, ‘ Morphol. Jabrb.,’ vol. 6, 1880, p. 581, Taf. xxx. t The unciform bone in Thylacinus appears to be formed by union of two elements. + “fiber die Extremitaten einer jungen Hatteria, ” von Dr. Franz Bater, in Tabor,‘Wien, Akad. Sitzber.,’ vol. 90 (Abtb. 1), 1885. § ‘ American Naturalist,’ February, 1885, p. 195. * || “ Quadrumana,” ‘ Todd, Cyclopaedia Anat.,’ vol. 4, part 1, 1852, p. 203.