page_title: Nautilus (genus)
section_title: Sensory Organs
hierarchical_section_title: Nautilus (genus) / Sensory Organs
context_page_description: Nautilus is a genus of cephalopods in the family Nautilidae. Species in this genus differ significantly in terms of morphology from those placed in the sister taxon Allonautilus. The oldest fossils of the genus are known from the Late Eocene Hoko River Formation, in Washington State and from Late-Eocene to Early Oligocene sediments in Kazakhstan. The oldest fossils of the modern species Nautilus pompilius are from Early Pleistocene sediments off the coast of Luzon in the Philippines.
  The common term Nautilus usually refers to any extant members of the Nautilidae family.The entire Nautilidae family, included all species in genus Nautilus and genus Allonautilus, was listed on Appendix-II of Convention on International Trade in Endangered Species of Wild Fauna and Flora.
  The current consensus is that the genus consists of four valid species, although this remains the subject of debate. Nautilus are typically found in shallow waters in tropical seas, mainly within the Indo-Pacific. The genus Nautilus has previously included several species represented in the fossil record, however these have since been reclassified, and the genus now only includes extant species.
context_section_description: Nautilus have unique sensory organs, which differ from related genera in several ways. Unlike other cephalopods, the eyes of Nautilus species lack ocular muscles, and instead move via a stalk, which contains both muscle and connective tissue. Additionally, Nautilus eyes lack any lens or cornea, and only have an aperture to allow for light.
  Below their eyes, Nautilus also feature rhinophores, which are small sacs with cilia. It has been suggested that this organ contains chemoreceptors, in order to detect food, or sample the surrounding water. Additionally, the tentacles of the Nautilus also perform several sensory functions. Their ocular and preocular tentacles feature cilia, and operate as mechanoreceptors, while their digital tentacles have been hypothesised to feature a range of receptor cells.
caption: A cross section of a Nautilus, revealing characteristic spiral shell, and retracted tentacles.
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