Nautilus pompilius Linnaeus, 1758 (type species of Nautilus)

Barord, Gregory J., Combosch, David J., Giribet, Gonzalo, Landman, Neil, Lemer, Sarah, Veloso, Job & Ward, Peter D., 2023, Three new species of Nautilus Linnaeus, 1758 (Mollusca, Cephalopoda) from the Coral Sea and South Pacific, ZooKeys 1143, pp. 51-69 : 51

Nautilus pompilius Linnaeus, 1758 (type species of Nautilus)

Diagnosis

(emended from Saunders et al. 2017). Shell compressed and involute, mature shell size of 140-220 mm mean diameter; 21% pigment coloration; umbilical callus always present. Sexual dimorphism prominent in mature animals: males larger, with a broader aperture than females. Growth lines sinuous, with ocular and hyponomic sinuses well developed in mature shells. Shell surface details from smooth to finely reticulate, because of minute parallel, serial scallops on growth lines in some isolated populations and species. Shell coloration variable, with brown, reddish- to purple-brown, irregular single and bifurcating stripes lacking on the body chamber at maturity. Two discrete color morphs found: stripes continue from venter to umbilicus, and stripes stop at mid flank, with a prominent white patch, sometimes with pale tan color, surrounding umbilicus. Hood covered with flat, white, warty protuberances, with two prominent white ridges extending down midline of hood. Anatomical aspects of the type species recently detailed by Shigeno et al. (2010).

Discussion.

A key note from the recent work of Saunders et al. (2017) was dedicated to coloration. In that paper, the explicit statement of there being two color-pattern morphs as a character defining N. pompilius was made. While this is found in the types of N. pompilius from Ambon, as well as in the new species we define here from Fiji, it is not known from N. belauensis , N. macromphalus , or N. vanuatuensis , whereas color stripes to the umbilicus are not known from N. repertus or N. stenomphalus . We thus feel justified in proposing this as but one more useful, species-level character when combined with other characters. Here we have used photographs published by Saunders et al. (2017) as means of measuring the percent coloration of the newly defined type species of N. pompilius .