Allonautilus scrobiculatus

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.[1] 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.[2] The species was thought to have gone extinct after 1986, but was rediscovered in July 2015.[3] According to The Telegraph, "the allonautilus scrobiculatus has inhabited the earth for 500 million years and has only been seen twice, until now".[4]

Allonautilus scrobiculatus
Allonautilus scrobiculatus off the coast of Papua New Guinea
Scientific classification
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Cephalopoda
Subclass:	Nautiloidea
Order:	Nautilida
Family:	Nautilidae
Genus:	Allonautilus
Species:	A. scrobiculatus
Binomial name
Allonautilus scrobiculatus (Lightfoot, 1786)
Synonyms
Nautilus scrobiculatus Lightfoot, ?Nautilus umbilicatus Linnaeus, 1758

Taxonomy

The genus Allonautilus, which contains a mere 2 species, is a sister genus of the Nautilus which contains 11 species, 5 of which are widely accepted as being distinct. The Allonautilus is very understudied and not much is known about it. However, the more commonly known sister genus, the Nautilus, has been known to natural historians since the renaissance. Nautiluses show very little speciation within the genus and are a distant cousin to the squid and octopus.

Description

A. scrobiculatus’ close lineage with nautiluses is juxtaposed by their very distinct morphological features which differ greatly from that of the nautilus. A very distinct feature that one will immediately notice is the organism’s thick, hairy, slime-covered shell. A. scrobiculatus is covered with white, irregularly shaped, multipronged papillae which extend from the surface of its hood.

The first illustration of the internal anatomy of Allonautilus scrobiculatus from a 1912 monograph by Arthur Willey.

In addition, it possesses a scrobiculate shell shape, meaning the shells have numerous grooves made into them unlike the Allonautilus perforatus, the only other organism in its genus; other than this, these two organisms share a very similar shell shape and coloration. A. scrobiculatus’ gills are similar in structure to those of the nautilus, however, differ in size proving smaller, with less folioles, in similarly sized nautilus specimens.

Periostracum

An unusual feature of Allonautilus scrobiculatus is its periostracum or "shell skin". The "shaggy" periostracumon is present on freshly caught samples, and is thickly interlayered, resembling slimy hair.[1]

Allonautilus scrobiculatus, or otherwise known as the crusty nautilus or fuzzy nautilus is a species of cephalopod. The species dates back roughly 500 million years and for decades, has impressed biologists and researchers with the species’ evolutionary grit, surviving for several millions of years, unchanged. A. scrobiculatus is considered by many to be a “living fossil”, similar to coelacanths and horseshoe crabs. A. scrobiculatus’ most recently sighting was in July 2015 by biologist Peter Ward of the University of Washington. Ward’s colleague, Bruce Saunders, a geologist from Bryn Mawr College was the one who had initially sighted the organism all the way back in 1984.

Distribution and habitat

A. scrobiculatus is primarily found in waters surrounding Papua New Guinea and the Solomon Islands. It tends to live in a very narrow range at further depths (roughly 500–1,300 ft), eluding many researchers and scientists. This is a result of the species’ intolerance to heat making it unable to live in too shallow of waters and the species’ “fail depth”, meaning it will die if venturing into too deep waters.

References

1. 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.
2. Pisor, D. L. (2005). Registry of World Record Size Shells (4th ed.). Snail's Pace Productions and ConchBooks. p. 93.
3. 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.
4. "World's rarest marine creature spotted after 30-year absence". Telegraph.co.uk. 28 August 2015.

• Norman, M. (2000). Cephalopods: A world guide. Hackenheim, DE: ConchBooks. p. 31.

External links

• "CephBase: Allonautilus scrobiculatus". Archived from the original on 2005.