Scolecia pluma Radtke, Hook, Campbell et Golubić, 2024

Key feature (diagnosis): S. pluma is a trace found slightly below the surface of pteropod shells. Hook (1991) called it “bottlebrush” (Fig. 18b) owing to the rod-like central filament with perpendicular extensions. The study of the development of this trace showed that it starts as a tunnel (a resin-cast filament), less than 1 μm in diameter, which conforms to the criteria identifying it as a member of the group of Scolecia traces (Fig. 18b). The later development observed along the Scolecia tunnel is seen in resin replication as flat foil-like lateral extensions, which under light microscope appear fuzzy and golden in colour resembling feathers, which suggests the name S. pluma. The main axes curve horizontally, are on average 70– 80 μm long and surrounded by numerous extremely fine “downy” extensions (ca 0.1–0.2 μm wide, up to 10 μm long) departing at right-angles from it, as well as penetrating deeper into the substrate (Fig. 18c). The main axis forms a submicron sized tunnel that determines the progression of the trace.