Planilisteks

Planilisteks are a fictional genus of planar invertebrates described in speculative biology and worldbuilding. They inhabit mineral-rich surface habitats, such as rock terraces and geothermal rims, and are notable for flat, tessellated bodies that resemble tiled pavements. Adults are small, typically ranging from a few millimeters to a couple of centimeters in diameter, with a flexible ventral surface equipped with cilia for gliding along slick substrates.

Anatomy and physiology: Planilisteks have a dorsoventrally flattened body and a simple nerve net. Gas exchange occurs by diffusion across the body surface, and there are no specialized respiratory organs. The gut is reduced and the organism relies on nearby biofilms for nutrients. Some species can regenerate from fragments, supporting local population recovery after disturbance. Reproduction is both sexual and asexual, with cross-fertilization common in stable populations and fragmentation enabling rapid spread when conditions permit.

Ecology and behavior: They prefer thin surface films of water on rock and mineral substrates, feeding on microalgae, biofilms, and filamentous fungi. Planilisteks are cryptic and usually nocturnal or crepuscular, moving slowly and sheltering in crevices to minimize desiccation. Temporary aggregations occur during mating seasons or after rain events, likely increasing encounter rates between individuals.

Taxonomy and usage: In fictional taxonomy, Planilisteks are placed in a hypothetical phylum Planilis, with the genus serving as a core unit for worldbuilding ecosystems. The name blends roots suggesting flatness with customary taxonomic suffixes. They appear in imagined biomes across volcanic and karst landscapes and are sometimes cited in discussions of bioinspired materials and surface ecology.