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Taxon profile

species

White-patch Nautilus
Nautilus stenomphalus G.B. Sowerby II, 1849

kingdom Animalia - animals »  phylum Mollusca - mollusks »  class Cephalopoda - cephalopods »  order Nautilida »  family Nautilidae »  genus Nautilus

Images

Nautilus stenomphalus - White-patch Nautilus

Author: Avon, C.

Taxon in country check-lists*

Asia: Philippines, Oceania: Australia (Queensland)

* List of countries might not be complete

Description

-15~20m, Taken by native divers, Sindangan Bay, Zamboanga del Norte, Mindanao, Philippines, 125.5mm., F
The « White-Patch Nautilus » is perhaps the most elusive of the five currently recognised recent nautilid species, characterised chiefly by the narrowly open umbilicus not covered by callus. Whether it actually is a true species or merely a form of N. pompilius has the subject of much debate. Nautilus with narrowly open umbilicus referred to as N. stenomphalus has been found widely throughout the Western Pacific, but the only truly reliable distinguishing character is in the soft parts: the hood of N. stenomphalus is covered in irregular papillae and highly textured. Such specimens are restricted to the Great Barrier Reef, Australia and N. stenomphalus sensu stricto is considered an endemic of this region although drift shells may be collected in other parts of the Western Pacific. The vernacular name originates from the fact that N. stenomphalus s.s. usually (not always) has a white band lacking flame pattern around the umbilicus region although this is seen in other nautilids as well. To add to the confusion, N. pompilius juveniles have narrowly open umbilicus and these are covered as the second whorl forms (approx. 75mm. in size for Philippines specimens); causing many such juveniles to be misidentified as N. stenomphalus. Very rarely this feature is retained to adulthood, and it is difficult to conclude whether the specimen shown is a drift shell of N. stenomphalus or a freak N. pompilius. Furthermore, a recent biogeography study (Bonacum et al., 2011) concluded that N. pompilius is not a true phylogenetic species but a cryptic assemblage of at least three paraphyletic populations; the only specimen identified as N. stenomphalus in the study fell within the N. pompilius clade from the same area. Although inconclusive, this suggests N. stenomphalus may only be a form of N. pompilius and agrees with many other recent studies which concluded that N. stenomphalus is a form or at most subspecies of N. pompilius; although N. pompilius itself seems to need a phylogenetic revision. Like all Nautilus N. stenomphalus is a carnivorous / scavenging cephalopod capable of adjusting its buoyancy by changing the liquid / gas composition within its chambered shell to move vertically in water column through its depth range of around -5~800m. Typical shell length around 150mm., very large specimens may exceed 180mm.
Avon C. 2016 . Gastropoda Pacifica.
Author: Jan Delsing

Links and literature

EN Australian Faunal Directory [ee64990b-4f13-4dd4-b13f-ba80062d8d00]

ABRS (2009-2019): Australian Faunal Directory [https://biodiversity.org.au/afd/home], Australian Biological Resources Study, Canberra [as Nautilus stenomphalus Sowerby, 1849]
Data retrieved on: 12 February 2015
EN Galli C.: WMSDB - Wolrdwide Mollusc Species Data Base July 10, 2013 [http://www.bagniliggia.it/WMSD/WMSDhome....] [as Nautilus stenomphalus Sowerby, 1848]
Data retrieved on: 23 November 2013

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