#nautilida

References:

Anthony, Franz. "500 million years of cephalopod fossils" Earth Archives, 19 Feb. 2018, https://eartharchives.org/articles/500-million-years-of-cephalopod-fossils/index.html

Klug, Christian, et al. "Preservation of nautilid soft parts inside and outside the conch interpreted as central nervous system, eyes, and renal concrements from the Lebanese Cenomanian." Swiss Journal of Palaeontology 140 (2021): 1-11. https://doi.org/10.1186/s13358-021-00229-9

Korn, Dieter, and Christian Klug. "Early Carboniferous coiled nautiloids from the Anti-Atlas (Morocco)." European Journal of Taxonomy 885 (2023): 156-194. https://doi.org/10.5852/ejt.2023.885.2199

Kröger, Björn, Jakob Vinther, and Dirk Fuchs. "Cephalopod origin and evolution: a congruent picture emerging from fossils, development and molecules: extant cephalopods are younger than previously realised and were under major selection to become agile, shell‐less predators." BioEssays 33.8 (2011): 602-613. https://doi.org/10.1002/bies.201100001

Mikesh, David L., and Brian F. Glenister. "Solenochilus Springeri (White & St. John, 1868) from the Pennsylvanian of Southern Iowa." Proceedings of the Iowa Academy of Science. Vol. 73. No. 1. 1966. https://scholarworks.uni.edu/pias/vol73/iss1/39/

Shchedukhin, A. Yu. "New Species of the Genus Acanthonautilus (Solenochilidae, Nautilida) from the Early Permian Shakhtau Reef (Cis-Urals)." Paleontological Journal 58.5 (2024): 506-515. https://www.researchgate.net/publication/384922837_New_Species_of_the_Genus_Acanthonautilus_Solenochilidae_Nautilida_from_the_Early_Permian_Shakhtau_Reef_Cis-Urals

Wikipedia contributors. “Nautilida” Wikipedia, 26 Nov. 2024, https://en.wikipedia.org/wiki/Nautilida

During the Middle Devonian, Nautilus species were more diverse, and their shells were more varied than those found in species of living Nautilus, ranging from curved (cyrtoconic), through loosely coiled (gyroconic), to tightly coiled forms, represented by the Rutoceratidae, Tetragonoceratidae, and Centroceratidae. Only a single genus, Cenoceras, with a shell similar to that of the modern nautilus, survived the Triassic extinction, at which time the entire Nautiloidea almost became extinct. They diversified again, but never reached the extent of diversity they had before the Triassic extinction. The nautilids were not as affected by the end Cretaceous mass extinction as the Ammonoids that became entirely extinct, possibly because their larger eggs were better suited to survive the conditions of that environment-changing event.

Nautiluses are the sole living cephalopods to have external shells. They can withdraw completely into their shell and close the opening with a leathery hood formed from two specially folded tentacles.

The nautilus has the extremely rare ability to withstand being brought to the surface from its deep natural habitat without suffering any apparent damage from the experience. Where fish or crustaceans brought up from such depths inevitably arrive dead, a nautilus will be unfazed despite the pressure change of as much as 80 standard atmospheres (1,200 psi).

Nautiluses have a seemingly simple brain, lacking the large complex brains of octopus, cuttlefish and squid, and had long been assumed to lack intelligence. But recent experiments have shown not only memory, but a changing response to the same event over time.

In a study in 2008, a group of Chambered Nautiluses (Nautilus pompilius) were given food as a bright blue light flashed until they began to associate the light with food, extending their tentacles every time the blue light was flashed. The blue light was again flashed without the food 3 minutes, 30 minutes, 1 hour, 6 hours, 12 hours, and 24 hours later. The nautiluses continued to respond excitedly to the blue light for up to 30 minutes after the experiment. An hour later they showed no reaction to the blue light. However, between 6 and 12 hours after the training, they again responded to the blue light, but more tentatively. The researchers concluded that nautiluses had memory capabilities similar to the "short-term" and "long-term memories" of the more advanced cephalopods, despite having different brain structures.

Female nautiluses spawn once per year and regenerate their gonads, making nautiluses the only cephalopods to be able to breed more than once in their lifetime.

Nautiluses may live for more than 20 years, which is exceptionally lengthy for a cephalopod, many of whom live less than 3 even in captivity and under ideal living conditions. However, nautiluses typically do not reach sexual maturity until they are about 15 years old, limiting their reproductive lifespan to often less than five years.