On Thecospondylus horneri, a new dinosaur from the Hastings Sand, indicated by the sacrum and the neural canal of the sacral region / by H.G. Seeley.

  • Seeley, H. G. (Harry Govier), 1839-1909.
Date:
1882
Catalogue details

Licence: Public Domain Mark

Credit: On Thecospondylus horneri, a new dinosaur from the Hastings Sand, indicated by the sacrum and the neural canal of the sacral region / 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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    [From the Quarterly Journal of the Geological Society for November 1882.] On Thecospondylus Horneri, a new Dinosaur from the Hastings Sand, indicated by the Sacrum and the Neural Canal of the Sacral Region. By Prof. H. G. Seeley, P.R.S., P.G.S. &c. [Plate XIX.] Dr. A. C. Horner, of Tonbridge, has obtained from the quarry at Southborough in the Hastings Sand, and intrusted to me, what I believe to be a unique specimen, so far as this country is concerned, exhibiting a mould of the entire neural cavity of the sacral region of a Dinosaur. Rut the specimen is nevertheless peculiarly tan- talizing, since the quarryman states that it is the only specimen of any kind that he has ever found in the quarry, and enough remains of bony tissue upon the cast to render it certain that the external mould of the sacrum, if not the bony tissue itself, might have been preserved. It is imperfect both anteriorly and posteriorly, but measures exactly 60 centimetres in length. The vertebra which are complete are five in number; each is 11 centim. long; but there is a small fragment in front which appears to show that there was another vertebra anteriorly (fig. 2, i), while the fragment of the posterior vertebra (fig. 2,7) admits of no question. We have thus a sacrum which certainly included six or seven vertebra, and may have comprised more. The bony tissue is preserved only upon the right side of three consecutive vertebrae. It is a thin film closely adherent to the cast, showing a cancellous structure external to the thin interior layer (fig. 1, b). This film is not more than from 1 to 2 millim. in thickness, and therefore gives no clue to the form of the sacrum; though other evidence leads me to believe that the bone was extremely thin, and pertained to an animal closely allied to Omithopsis. The neural chamber of this sacrum, besides being remarkable for its great length, is singularly compressed from side to side (fig. 2), and expanded from below upward (fig. 1). It is at first sight no easy task to distinguish the back from the front. In Anoplosaurus curtonotus I figured the neural canal of a Dinosaur (Quart. Journ. Geol. Soc. vol. xxxv. pi. xxxiv.), which seemed to prove that the anterior third of the neural canal is the part which has the greatest transverse expansion. Subsequently Prof. Marsh (Am. Journ. Sci. vol. xxi. pi. 6, 1881) figured a cast of the neural cavity of Stegosaurus, in which the sacral canal is about 26 centim. long, and, where highest, 7 6 centim. high, and 4\3 centim. wide in front. Anoplosaurus from the Cambridge Greensand had the sacral nerves of moderate size; but the casts of the foramina between the vertebra;, which are represented in Professor Marsh’s plate, are deep and narrow, and two of them extend the entire height of the neural cavity. In regarding the larger portion of the sacrum as anterior, we follow what may be termed Dinosaurian precedents; and when we