An anomalous fossil organism, possibly a new type of chordate, from the upper silurian of lesmahagow, lanarkshire — Ainiktozoon loganense , gen. et sp. nov

Abstract

29 fossils, apparently of the same species, were examined and a reconstruction made. The most definite features are a double-walled ovoid capsule, 1-3 in. long, its walls showing striae and its upper truncated end bearing a fringe of cirri; contiguous to and at right angles to the capsule are 2 segmented rods, converging at their distal ends. The upper rod bears lobe-like intersegmental processes, the lower larger rod has on each segment a spine bifurcated at its base. In the less definite area on the opposite side of the capsule to the rods are several striated fascicles, and in some specimens an irregular patch of papillae and an auriculate structure. Reasons for excluding the organism from any known class of invertebrate are given, and it is concluded that if the capsule and cirri are interpreted as a filtering chamber for food, the segmented rods can be regarded as an elaborated homologue of the tail of the tadpole larva of a Tunicate. The organism, allied to the Urochorda, is therefore provisionally assigned to the Chordata under the name given in the title.