Pharaonella amanyu Kato & Ohsuga

Kato, Makoto, Yamamori, Luna, Goto, Ryutaro, Tsubaki, Remi & Ohsuga, Ken, 2017, A new large tellinid species of the genus Pharaonella from the Ryukyu Archipelago, Japan (Mollusca, Bivalvia), ZooKeys 705, pp. 1-13 : 1-4

Pharaonella amanyu Kato & Ohsuga sp. n. Figs 2C, 3 A–G, 4A, 5A

Description.

Shell. Shell elongate, narrow, subequilateral; inequivalve; anterior section longer than posterior section (Fig. 3 A–C); posterior end rostrate, slightly twisted to right (Fig. 3E); weakly gaping posteriorly; left valve glossy, smooth, with faint radials; right valve weakly commarginal ridged on rostrum; exterior color orange to pink, sometimes with fine pale rays emanating from umbo (although the colour of the shell tends to fade once the animal has died); periostracum thin, shiny, slightly iridescent; interior orange to pink with yellow tint in central section; umbones small, posteriorly displaced and touching each other; hinge ligament external, short, and situated in ligamental groove; right valve hinge with 2 elongate lateral teeth, 1 oblique anterior cardinal tooth plus 1 bifid posterior cardinal tooth (Fig. 3F); left valve hinge with 2 distal elongate laterals, 1 trigonal anterior and 1 laminate posterior cardinal tooth (Fig. 3G); posterior edentulous space expanded in both valves; pallial sinus reaching horizontal midline in height of the shell and extending beyond vertical midline in length, confluent with pallial line at middle of shell (Fig. 3D); adductor muscle scars subequal and suborbicular.

Anatomy. Mantle and foot orange, thus similar to colour of shell (Fig. 4A), contrasting with creamy white of those of Tonganaella tongana (Fig. 4B). Excurrent and incurrent siphons long, similar to each other in length. Siphons able to be extended further than shell length when alive.

Labial palps well developed in comparison with demibranchs. Outer and inner hemipalps elongate-triangular (Fig. 5A), posterior extension of hemipalp weaker than those of T. tongana (Fig. 5B) and P. sieboldii (Fig. 5C). Inner surfaces of hemipalps have palp folds, which originating from hemipalp intersection spreading toward palp dorsal edge; folds becoming relatively wider distally; distal edges of folds of outer hemipalp form swellings (Fig. 5A).

Type material.

Holotype: NSMT-Mo 78982, paired valves, length 69 mm, height 32 mm (Figs 3A, B, E, 4A), collected alive by M. Kato on 26 May 2013. Paratype: NSMT-Mo 78983, right valve, length 80 mm, height 36 mm (Fig. 3C, G), collected by K. Ohsuga on 28 April 2006; KUZ-Z1878, left valve, length 73 mm, height 33 mm (Fig. 3D, F), same data as the former paratype; KUZ-Z1879, right valve, length 77 mm, height 34 mm, collected by K. Ohsuga at type locality13 July 1995.

Type locality.

Edateku Island, Uken, Kagoshima Prefecture, Japan (28°17'26.08"N, 129°13'9.09"E); in sand of subtidal sand bank.

Distribution.

In addition to the type locality, the species has also been recorded at Kasari Bay on Amami-Oshima Island, but only by empty shells.

Etymology.

The epithet amanyu alludes to the mythical archaic peaceful era of Amami Islands, symbolising the undisturbed coastal ecosystem harbouring this bivalve species. It is used as a noun in apposition.

Japanese name.

Aman’yu-beni-gai.

Habitat.

The bivalve was found deeply buried (about 15 cm) in subtidal sandy bottom.