English: Scientific Name: Lanarkia, Loganellia

Comments: Thelodonts are a still poorly known group of Silurian and Devonian jawless vertebrates, whose dermal skeleton consists of minute scales. Most thelodonts have a dorsoventrally depressed body and head, the gill openings being situated on the ventral side. It is assumed that the snout was more or less as in primitive galeaspids; that is, with a broad, inhalent median opening and a slightly ventral mouth. Among the flat-bodied forms are Lanarkia (top left), provided with long, spine-shaped scales, and Loganellia (top right and middle). Other thelodonts, such as an unnamed form from the Devonian of Canada (bottom) are deep-bodied, with lateral gill openings and a very large, forked tail.

Reference: Based on Turner, S. 1991. Monophyly and interrelationships of the Thelodonti.In Early vertebrates and related problems of evolutionary biology (ed. M. M. Chang, Y. H. Liu, and G. R. Zhang), pp. 87-119. Science Press, Beijing. AND Turner, S. 1992. Thelodont lifestyles. In Fossil fishes as living animals (ed. E. Mark-Kurik), Akademia, 1:21-40. AND Wilson & Cadwell 1993