1911 Encyclopædia Britannica/Palaeospondylus
|From British Museum Guide to Fossil Reptiles and Fishes, by permission of the Trustees.|
|Palaeospondylus gunni, restored by Dr R. H. Traquair.|
(Nearly twice nat. size.)
PALAEOSPONDYLUS, a small fish-like organism, of which the skeleton is found fossil in the Middle Old Red Sandstone of Achanarras, near Thurso, Caithness. It was thus named (Gr. ancient vertebra) by Dr R. H. Traquair in 1890, in allusion to its well-developed vertebral rings; and its structure was studied in detail in 1903 by Professor and Miss Sollas, who succeeded in making enlarged models of the fossil in wax. The skeleton as preserved is carbonized, and indicates an eel shaped animal from 3 to 5 cm., in length. The skull, which must have consisted of hardened cartilage, exhibits pairs of nasal and auditory capsules, with a gill-apparatus below its hinder part, but no indications of ordinary jaws. The anterior opening of the brain-case is surrounded by a ring of hard cirri. A pair of “post-bronchial plates” projects backwards from the head. The vertebral axis shows a series of broad rings, with distinct neural arches, but no ribs. Towards the end of the body both neural and haemal arches are continued into forked radial cartilages, which support a median fin. There are no traces either of paired fins or of dermal armour. The affinities of Palaeospondylus are doubtful, but it is probably related to the contemporaneous armoured Ostracoderms.
References.—R. H. Traquair, paper in Proc. Roy. Phys. Soc. Edin., xii. 312, (1894); W. J. Sollas and I. B. J. Sollas, paper in Phil. Trans. Roy. Soc. (1903 B.).