Fig. 3: Surface characteristics of the Antarctic scallop’s shell features.

a–c Terminology and schematics of features on the shell surface, a, b in-plane, and c section view. d, e Macroscopic images in visible light of the Antarctic scallop’s shell surface without magnification. The shell is covered by a thin, proteinaceous covering (periostracum), under which the calcitic material lies throughout the thickness of the shell. Radial rounded, primary ridges, and concentric growth rings are visible. f–h Scanning electron micrographs showing increasing magnification. f Concentric growth rings separating repeating series of g radial micro-ridges (c. 20 µm peak-to-peak). h Small protuberances are irregularly dispersed throughout the radial micro-valleys (Supplementary Fig. 3). Shells are oriented with the umbo at the top in all panels, except c. Shells of temperate control species are substantially rougher and less ordered than those of the Antarctic scallop (Supplementary Fig. 2).