Description of the skeleton of an extinct gigantic sloth : Mylodon robutus, Owen, with observations on the osteology, natural affinities, and probable habits of the megatherioid quadrupeds in general / by Richard Owen.

  • Richard Owen
Date:
1842
Catalogue details

Licence: Public Domain Mark

Credit: Description of the skeleton of an extinct gigantic sloth : Mylodon robutus, Owen, with observations on the osteology, natural affinities, and probable habits of the megatherioid quadrupeds in general / by Richard Owen. Source: Wellcome Collection.

Provider: This material has been provided by King’s College London. The original may be consulted at King’s College London.

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    Description of the Teeth. The teeth of the Mylodon are eighteen in number, arranged according to the following formula, |^ = 18: they are simple, long, fangless, and of the same thickness from the implanted to the exposed end; the former is excavated by a deep conical pulp-cavity*, the latter worn into a shallow depression, with a raised obtuse margin. The forms of the grinding surfaces are so accurately given in Plates IV. and VI.,—those of the upper jaw being represented of the natural size, —that verbal description may be dispensed with. The exserted parts or crowns are unusually worn down, and rather obliquely, so as not to reach the level of the inner wall of the socket in the upper jaw, nor that of the outer wall in the lower jawf. The first tooth of the upper jaw, which, as the figures express, is separated by a marked interval from the rest, is also more curved, the convexity being turned forwards; the posterior teeth are nearly straight : their length is about three inches, the first is a few lines longer than the rest. In the lower jaw, the first tooth opposes the second upper molar when the jaws are naturally closed; but the nature of the joint would allow considerable extent of motion forwards and backwards, and the bony attachments for the masseter show its peculiar adaptation for working the jaw extensively in the hori- zontal direction. The grinding surface of the first lower molar is worn down obliquely, the anterior edge being the highest; its curvature is outwards and for- wards. The last tooth of the lower jaw, which is the largest and most complex of the series, is slightly bent with the convexity turned inwards. Each tooth has a central body of vascular dentine:]:, in which the medullary canals run parallel with each other obliquely to the axis of the tooth, and form loops at the periphery of the central constituent: this is inclosed by a cylinder of hard unvascular dentine §, about oi^e line and a half in thickness : the outer covering consists of cement 1|, about one-third of a line in thickness. The unvas- cular dentine, as the densest constituent, forms the prominent ridge inclosing the central depression of the grinding surface. * This is indicated by the dotted line in the teeth figured in Plate V. figs. 5 and 6. t In Plate II. the teeth are figured a little more protruded than in the skull itself. i Plate XXIV. fig. 3. a. § Ibid. b. || Ibid. c.