 Engravings in open spaces like cliffsides are generally of spirals and curvilinear shapes, while engravings in enclosed caves and shelters depict faces and boats.The same motifs can also be seen in dendroglyphs on living trees.With the possible exception of rongorongo on Rapa Nui, Austronesians did not have an indigenous writing system but rather adopted or developed writing systems after contact with various non-Austronesian cultures.