Description of two new species of the genus Viriola Jousseaume, 1884 (Gastropoda: Triphoridae) from Vietnam

Researchers from the Joint Vietnam-Russia Tropical Science and Technology Research Center have recently described two new species of the genus Viriola (Gastropoda: Triphoridae) in Vietnam. These discoveries were made during field surveys conducted in the Tho Chu Islands and the Spratly Islands between 2019-2020 and 2023. The two newly identified species, Viriola namyitensis and Viriola thochuensis, possess distinct morphological characteristics that differentiate them from other known species within the genus.

The names of these species reflect their respective geographic origins. Viriola namyitensis is named after Namyit Island in the Spratly Islands, while Viriola thochuensis is named after the Tho Chu Islands. Naming species based on their places of origin not only honors the geographic origins of the specimens but also highlights the biological significance of these remote marine regions.

Viriola namyitensis possesses a relatively elongate, conical shell that is flat dorsally and convex ventrally, with three smooth spiral cords. The shell is yellowish-brown, featuring white streaks on the first spiral cord, white granules on the second, and reddish-brown coloration between the first and third spiral cords (Figures 1, 2). (Viriola namyitensis is rather long, cyrtoconoid, flat above and convex below. The teleoconch is yellowish brown with white blotches on the first spiral cord, white granules on the second spiral cord, and reddish brown between spiral cords 1–3 (Fig. 1, 2).

In contrast, Viriola thochuensis has a shorter, conical shell with a broad base. The shell background is white, marked with patches ranging from light to dark brown. The third spiral cord displays more prominent coloration compared to the other two (Figures 1, 3). (Viriola thochuensis is short, conoid, rather flat sides, and a wide base. The shell has a white background with patches of brown to dark brown. The third spiral cord on the teleconch whorls is more brightly colored than the first and second spiral cords (Fig. 1, 3).

The discovery of these two new gastropod species contributes to the expanding inventory of marine mollusks both globally and within Vietnam. It also underscores the importance of continued research aimed at uncovering the biodiversity of offshore marine ecosystems.

Fig. 1. A–B. Viriola abbotti (Baker & Spicer, 1935), C–E. V. namyitensis n. sp., F–G. V. bayani Jousseaume, 1884, H–I. V. intergranosa (Hervier, 1898), J–P. V. thochuensis n. sp.

Fig. 2. Viriola namyitensis, A. Front view. B. Dosal view. C. Last whorl. D. Peristome. E. Teleoconch microsculpture. F. Protoconch. G. First protoconch whorl.

Fig. 3. Viriola thochuensis, A. Front view. B. Dorsal view. C. Last whorl. D. Peristome. E. Teleoconch microsculpture. F. Protoconch. G. First protoconch whorl.

Source: Tai-Tu NGUYEN, Duong T.T. HOANG (2025). Description of new species of the genus Viriola Jousseaume, 1884 (Gastropoda: Triphoridae) from Vietnam, Ruthenica, 2025, vol. 35, No. 2: 53-64.

Author: Nguyen Tai Tu (Institute of Tropical ecology)

Ngoc Nguyen translated