Turriplaca thomseni (Roijackers and Siemensma, 1988) Nicholls, 2012
basionym Rabdiophrys thomseni Roijackers and Siemensma (1988)

Diagnosis: Cells covered by both plate- and spine-scales. The spine-scales are straight, completely bent or have a straight tubular part and a curved lamella. The plate-scales are oval in outline, with a diameter of 3.0-5.4 µm. The proximal plate is perforated by many minute pores; the distal plate has 6-9 holes and is fused to the proximal plate peripherally and by many internal ridges, forming hexagonal patterns of black dots as seen by TEM. The spine-scales are 2.4-6.1 µm long. They consist of a hollow tube, terminating proximally in several struts by which the tube is fused to the base plate, and distally in up to 6 teeth. There are, however, distally some extra holes in the tubular part of the spine-scale near to the struts, thus giving a much more complicated structure. The 2 middle spines at the apex of some spine-scales are very extended and reach about the same length as the shaft (2 µm); these 2 middle spines are fused by a very thin lamella, thus forming 2 circular holes, when seen from the top of the spine-scale. In other spine-scales a third spine is extended and fused to the two middle spines, giving 3 circular holes, when viewed from the top. Then there are spine-scales that have extremely variable structures at the 2 or 3 extended spines.

Remarks: The plate-scales are identical to those of Pinaciophora rubicunda. I have collected both species together. Turriplaca thomseni differs from R. denticulata in having very variable spine-scales with their apex divided into 2 or 3 holes.
T. thomseni was collected from algae along the southern coast of Sweden, between Mörrum and Karlshamn, August 1986. It is also known from brackish water in Denmark (Thomsen 1978: Fig. 15). The plate-scale, illustrated by Thomsen (1979, Fig. 53) and identified as P. denticulata, probably belongs to T. thomseni.