|Allonautilus scrobiculatus shell with periostracum removed|
Allonautilus scrobiculatus, also known as the crusty nautilus or fuzzy nautilus, is a species of nautilus native to the waters around New Guinea, specifically New Britain and Milne Bay, and the Solomon Islands. A. scrobiculatus is instantly recognizable by the large open umbilicus, which is around 20% of the shell diameter at its widest point. This species, along with the closely related A. perforatus, were originally placed in the genus Nautilus, but have recently been given their own genus on account of significant morphological differences. The most obvious are features of the shell, including crease and an encrusting layer (periostracum) that covers most of the shell. Gills and reproductive structures also differ significantly from members of the genus Nautilus. The shell is usually up to around 18 cm in diameter, although the largest specimen ever recorded measured 21.5 cm. The species was thought to have gone extinct after 1986, but was rediscovered in July 2015. According to The Telegraph, "the allonautilus scrobiculatus has inhabited the earth for 500 million years and has only been seen twice, until now".
An unusual feature of Allonautilus scrobiculatus is its periostracum. The "shaggy" periostracumon is present on freshly caught samples, and is thickly interlayered, resembling slimy hair.
- Ward, P.D. & W.B. Saunders 1997. Allonautilus: a new genus of living nautiloid cephalopod and its bearing on phylogeny of the Nautilida. Journal of Paleontology 71(6): 1054–1064.
- Pisor, D. L. (2005). Registry of World Record Size Shells (4th ed.). Snail's Pace Productions and ConchBooks. p. 93.
- Urton, James (25 August 2015). "Rare nautilus sighted for the first time in three decades". UW Today. University of Washington. Archived from the original on 26 August 2015. Retrieved 1 September 2015.
- "World's rarest marine creature spotted after 30-year absence". Telegraph.co.uk. 28 August 2015.
- Norman, M. 2000. Cephalopods: A World Guide. Hackenheim, ConchBooks, p. 31.
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