Fig. 4

Proposed interaction between some papillae and unculi types and some substrate occurring naturally in the habitat (stiff and smooth as e.g. rounded stone or wood; stiff and rough as e.g. wood or stone; soft substrate as e.g. plant covers on stone or wood). The grey color gradients in the structures relate to the mechanical properties (black = stiff; white = flexible), which are inferred from manipulation of structures and by documenting the artefacts caused by drying and shrinking. Purple boxes identify the structures, which probably facilitate interlocking (interlocking type) and the blue boxes identify the structures, which probably support adhesion to the target surface (adhesion type). Hexagons show, how presumably well the specific structures enable attachment with the target surface (orange = not well, yellow = medium, green = well). A Flat papillae with no unculi but a bulky surface. B Medium papillae with suction cups. C Medium papillae with hooks. D Medium papillae with mushrooms. E Medium papillae with small mushrooms. F Medium papillae with honey-combed unculi. G Medium papillae with long filaments. H Medium papillae with folds