On the structure of the maxillary and dental organs of the iguanodon / by Gideon Algernon Mantell.

  • Gideon Mantell
Date:
1848
Catalogue details

Licence: Public Domain Mark

Credit: On the structure of the maxillary and dental organs of the iguanodon / by Gideon Algernon Mantell. 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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    parapet, deeply furrowed on the inner side, as seen in this view, by the sockets for the mature teeth (/,/). Strongly-defined ridges occupy the interspaces, and rising above the sockets produce a sharp crenated upper border. The alveolar space is protected on the inner side by a moderately strong plate or wall, which must originally have nearly equalled the outer parapet in height, but is now in a great measure broken away: within this process the germs of the successional teeth were developed. The mode of implantation of the teeth appears to have been intermediate between the pleurodont and thecodont types ; for the teeth were not anchylosed to the alveolar wall as in the Iguanas, but free as in the Crocodiles ; yet as the ridges that separate the dental sockets are smooth and rounded, it may be inferred that these were not rendered complete alveoli by transverse plates extending from the outer to the inner parapet, as is the case in the Megalosaurus*. The dental sockets diminish in size, but somewhat irregularly, from the posterior to the anterior termination of the alveolar process; and the latter suffers a corre- sponding diminution in breadth, and terminates suddenly at the distance of five inches from the front. At this point the upper margin becomes attenuated and contracted in a vertical direction, and descending with a gentle curve, expands horizontally and mesially to unite at the symphysial suture (s) with the opposite ramus, the anterior part of the jaw being edentulous. From the fortunate preservation of two successional teeth in their original position, the mode of dental development in the Iguanodon is clearly demonstrated. The coronal portion of the tooth was first formed, as seen in the germ, Plate XVI. fig. 1, a ; and the entire crown was completed (fig. 1 ,b) before the secretion of the shank or fang commenced, as in the existing Saurians. The formative pulp was situated in a distinct depression or cavity, on the inner side of the root of the tooth it was destined to supplant: this is obvious by the positions of the teeth above described ; and also by the remains of a third germ towards the posterior part (fig. 1, c). Although the peculiar characters of the molars of the Iguanodon were described somewhat in detail in my former communications, and the present fossil confirms in every essential particular the inferences suggested by the detached teeth, as stated in my memoir of 1825, yet several new and important points relating to the development and functions of the dental organs, are elucidated by the new acquisition which Capt. Brickenden’s researches have brought to light. The second tooth (Plate XVI. fig. 1, b) which occupies its natural position in the alveolar space, consists of the entire crown, having the serrated margin as perfect as in the recent state; and this is the first evidence I have obtained as to the mode in which the teeth were implanted. The flat enamelled front, characterized by its longitudinal ridges, is placed mesially, and parallel to, and within the inner alveolar wall; the smooth convex face filling up a depression in the outer parapet, in the interspace of two sockets of the mature molars. This position is the reverse of that in which the successional teeth in the Iguana are developed ; for in that reptile the coronal germ occupies the same relative place as * See Dr. Bucki.and’s Bridgewater Essay, Plate 23.
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