Nautilus vanuatuensis, Barord & Combosch & Giribet & Landman & Lemer & Veloso & Ward, 2023

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 vanuatuensis sp. nov.

Fig. 6

Type material.

Holotype: accessioned at American Museum of Natural History, AMNH 131861 (Fig. 6a ). Collected from Mele Bay, Port Vila, Vanuatu, 17°43'21.61"S, 168°16'01.98"E, at a depth of 185 m on 20 July 2004. Paratypes: accessioned at American Museum of Natural History, AMNH 131856 (Fig. 6b ), same collecting data as holotype.

Diagnosis.

The following characteristics distinguish Nautilus vanuatuensis sp. nov. from other species within the genus Nautilus : 40-50% shell coloration, more than any other Nautilus species with a plugged umbilicus; pigmentation always composed of stripes extending from venter to umbilicus (no specimens show the "white patch" coloration of N. pompilius or N. vitiensis sp. nov.). This species is most similar in size, color pattern, and degree of shell covered by pigment to N. macromphalus , but the umbilical plug is always missing in the latter species.

Description.

Nautiliconic, shell with umbilical plug, whorl higher than broad at maturity. Periostracum entirely absent in mature and even near-mature specimens. Shell surface ornamented with growth lines parallel to apertural shape. No cross-hatching or ornament perpendicular to growth lines. Hood morphology consisting of low, elliptical white protuberances barely projecting above hood surface on either side of two long, raised, parallel white stripes running centrally down hood from shell whorl to aperture. White protuberances found between stripes on entire central section; they are low and non-digitate at their terminal ends (see hood details on Suppl. material 3: video 3; Fig. 7 ). Mean diameter of adult shell is 156.6 mm, s.d. 5.237 (see range of measured specimens in Table 1 ).

Discussion.

Nautilus vanuatuensis is virtually identical in size, color pattern, and degree of shell covered by pigment to N. macromphalus in New Caledonia, which is the Nautilus species geographically closest to Vanuatu. The new species we define here differs by always having an umbilical plug. Both species are ecologically similar in that mature specimens are commonly observed in very shallow water (up to 5 m depth) off Vanuatu and New Caledonia. As species show the similar, high degree of pigmentation, we assume that the shallow-water habitat visitation by both is the reason for their high level of pigmentation.

Etymology.

The specific epithet, an adjective, refers to the type locality, Vanuatu, where all the known specimens have been collected.

Habitat and distribution.

Nautilus vanuatuensis inhabits sites within Mele Bay, Vanuatu. Specimens were collected and filmed (Suppl. material 3: video 3) at depths of 200-400 m.

Figures

Figure 6. Lateral view of Nautilus vanuatuensis sp. nov. A holotype AMNH 131861 B paratype AMNH 131856.

Figure 7. Underwater photos of living Nautilus A, B N. samoaensis sp. nov. C N. vanuatuensis sp. nov. D N. vitiensis sp. nov.