Patelloida parva, Paran & Sasaki & Asakura & Nakano, 2025

Genus Patelloida Quoy & Gaimard, 1834 View in CoL

Patelloida parva n. sp. ( Figs. 3 View Fig ; S 2 View Fig ) urn:lsid:zoobank.org:pub:

Patelloida sp. — Sasaki, 1999:39.

Type material: Holotype: University Museum , The University of Tokyo ( UMUT)- RM34074 View Materials (see Fig. 3p View Fig ), Shionomisaki, Kushimoto, Wakayama., Japan.

Selected paratypes: Paratype 1 ( UMUTRM 34046), Shionomisaki, Kushimoto, Wakayama., Japan. Paratype 2 ( UMUT-RM 34048), Shionomisaki, Kushimoto, Wakayama., Japan. Paratype 3 ( UMUT-RM 34061), Kashiwajima, Kochi., Japan. Paratype 4 ( UMUT-RM 34062), Kashiwajima, Kochi., Japan. Paratype 5 ( UMUT-RM 34049), Shionomisaki, Kushimoto, Wakayama., Japan. Paratype 6 ( UMUT-RM 34065), Shionomisaki, Kushimoto, Wakayama., Japan.

Type locality: Ogokuda Beach, Cape Shionomisaki, Kushimoto, Wakayama Prefecture, Japan.

Description: Shell ( Fig. 3 View Fig ) conical. Sculpture consists usually of 8–12 radial ribs, highly variable in thickness. The major ribs are thicker, while thinner secondary ribs intersperse between the primary ones. The apex is positioned anteriorly, projecting ribs in a distinctive stellate pattern. External shell coloration ranges from greyish blue to brown reticulate markings, complemented by a whitish eroded apex.

Ventral view reveals a smooth and lustrous interior, featuring blue and yellow shadings on the apex, along with white or blue projections in the ribs. Dark blue to black margins encircle the shell. Measurements indicate variations in shell length ( 9.4–16.5 mm), width ( 6.6–12.8 mm), and height ( 1.8–6.7 mm) ( Table S1).

Radula morphology: The radular structure of Patelloida parva n. sp. is docoglossate, featuring three pairs of lateral teeth and two pairs of marginal teeth, as illustrated in figure 4a. The first lateral teeth exhibit tapering stalks culminating in triangular pointed ends. The second lateral teeth are distinctive, extending prominently with a curved, kite-like tongue, featuring a deeply dented base. Notably, the third lateral teeth are notably thin and pointed, positioned on the sides of the second lateral teeth. Stacked on the upper portion of each other, the marginal teeth share a high degree of similarity, characterized by narrow stalks and rounded cusps.

The radula sac comprises approximately 50 rows of teeth ( Fig. 4b View Fig ), with Row 1 representing the oldest set of teeth located in the mouth. Rows 1–30 are characterized by substantial mineralization and exhibit minimal variation. In contrast, Rows 31–50 show weaker mineralization and display observable variation in size and shape. The radula ribbon, maintaining a copper-like hue, gradually lightens towards the younger, posterior end.

Etymology: The specific name parva is derived from the Latin word parvus, meaning “small,” in reference to the diminutive size of the species compared to its genetically closest relative, Patelloida saccharinoides , and the morphologically similar species, Patelloida saccharina and Patelloida lanx .

Distribution: Patelloida parva n. sp. is limited to the intertidal zones in the southernmost parts of Kochi and Wakayama Prefectures, Japan facing the Pacific Ocean. Museum archives have recorded its occurrence in Amami-Oshima Island in the Ryukyu Archipelago.