Nautilus samoaensis, 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 samoaensis sp. nov.

Fig. 5

Type material.

Holotype: accessioned at the Natural History Museum, Smithsonian Institution, USNM 816658 (Fig. 5a ). Collected in Taema Bank, American Samoa, 14°16'32.27"S, 170°41'12.58"W, between depths of 280 and 310 m on 22 July 1986. Paratypes: accessioned at Natural History Museum, Smithsonian Institution, USNM 816708 (Fig. 5b ), same collecting data as holotype. Accessioned at American Museum of Natural History, AMNH 81945, same collecting data as holotype.

Diagnosis.

The following characteristics distinguish Nautilus samoaensis sp. nov. from other species within the genus Nautilus : 32-36% pigment coloration, more than Nautilus vitiensis sp. nov. and less than Nautilus vanuatuensis sp. nov.; composed of stripes beginning at venter and then curving around in an arc pointing toward aperture as they finally intersect with umbilical region. As noted by Saunders et al. (1989), there is a faint, growth-line sized pattern of annual rings similar in scale and morphology to that found in Nautilus belauensis , but far less marked. Shell color pattern most unique of all Nautilus species composed of multiple, branching stripes that have a rearward projection after descending from venter. No other known Nautilus species shows this color pattern, and shells are recognized because of this unique coloration pattern, coloration percentage, and shell shape like N. pompilius .

Description.

Nautiliconic, shell with umbilical plug, whorl higher than broad at maturity. Periostracum entirely absent in mature and near-mature specimens. Shell striping with a series of concentric circles that overlap in a way unique to this species, with a single exception, although this has been referred to as a “zigzag” pattern elsewhere. White protuberances found between stripes and outside of stripes on the entire central section (see hood details in Suppl. material 2: video 2; Fig. 7 ). Average shell diameter 171.3, s.d. 5.029 (see range of measured specimens in Table 1 ).

Remarks.

A single shell described and illustrated by Saunders et al. (1989) shows an identical pattern to that seen on every observed specimen of Nautilus samoaensis sp. nov., but that specimen (USNM 816705) is said to have come from Fiji. However, in the many Fijian nautilus shells with published figures, or examined by us, there has never been another with this pattern, nor has there ever been a shell of this size found in Fiji, so this specimen may have been mislabeled.

The color in freshly caught animals and as viewed underwater has a more magenta hue than is seen in dried shells from this locality. This has not been quantified, however, and as in all other known species, the color changes after the shell dries, red hues are lost, and the shell acquires a uniform brown color.

Etymology.

The specific epithet, an adjective, refers to the type locality, American Samoa.

Habitat and distribution.

Nautilus samoaensis sp. nov. inhabits areas near Pago Pago, American Samoa. Specimens were collected and filmed (Suppl. material 2: video 2) at depths between 200 and 400 m.

Figures

Figure 5. Lateral view of N. samoaensis sp. nov. A holotype USNM 816658 B paratype USNM 816708.

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