Secondary electron images of gekkotan eggshells.

Abstract

Each column is outer, radial, and inner views, respectively. White and black bars on the side of a central column represent the boundary between the layers mentioned in the text and S1 Text. Outside of eggshell is up. See S2–S8 Figs for details. (A) Gekko gecko. Ribbon-like structures in A3 are remnants of the shell membrane. (B) Paroedura pictus. White arrows in B1 point pore-like structures. Note columnar structure (white arrows) and ridge-like ornamentations (black arrows) in B2. The inner surface is characterized by a lot of pits. (C) Paroedura stumpfii. White arrows in C1 mark the fragments of sawdust so that they should be neglected. Note the absence of columnar structure in the plain layer and the presence of ornamentation (a white arrow) in C2. Protruding calcite concretions are distributed in C3 (white arrows). (D) Phelsuma grandis. Note that the boundary between the blocky and columnar layers in D2 is very similar to the inner surface of other rigid gekkotan eggshells where needle-like structure exists (a white arrow). (E) Correlophus ciliatus. The calcareous layer is weakly columnar in shape and morphologically different from the very thin calcareous layer of derived squamate eggshells. A white arrow in E3 marks the margin of the boundary layer. (F) Rhacodactylus leachianus. The gradual boundary between the capsule-like and flattened granules is marked in F1 (a white arrow) in the outer surface. Note the convex mounds in the boundary layer (white arrows) in F3. (G) Eublepharis macularius. Note that protein fibers near the calcareous layer have wave-like undulation in G2 (white arrows). The outline of eggshell is similar to those of scincid lizard eggshells [39].</p