Ennucula ipepa, Simone, 2024

Genus Ennucula Iredale, 1931 View in CoL Ennucula ipepa , new species

( Fig. 39 View Figure 39 ) https://zoobank.org/ D91C55F5-3B23-4C4A-B4A5-AD0A130D1826

Types: Holotype MZSP 166732 View Materials , shell . Paratypes: MZSP 166733, 1 shell, MZSP 166629, 12 shells, 58 valves, MNRJ, 2 shells + 3 valves, MNHN-IM-2000-39810, 1 shell + 9 valves, all from type locality.

Type locality: BRAZIL. Espírito Santo ; ItaÚnas, off, Abrolhos slope, 19°40.6′S 37°48.1′W, 790-940 m [ MD55 sta. CB77 , 27.v.1987] GoogleMaps .

Diagnosis: Species from off SE Brazil of ~ 5 mm, with almost central umbo. Ligament almost perpendicular. Hinge with 11-12 anterior and 8-9 posterior teeth.

Description: Shell of ~ 5 mm; outline rounded; ~1.2 times longer than heigh; walls slightly thin. Umbo relatively blunt, slightly prominent; almost central slightly dislocated anteriorly, with umbonal angulation of ~110°. Anterior and posterior umbonal edges almost symmetrical, both convex, flattened in edges, almost wing-like; posterior edge slightly shorter and more vertical; anterior edge longer and slightly more convex; ventral edge widely rounded ( Fig. 39 View Figure 39 A-B, D-G, J-M) with weak, blunt posterior beak. Very weak, oblique anterior carina. Maximum inflation ~50% of length ( Fig. 39C View Figure 39 ). outer surface glossy, shining; sculpture commarginal, narrow, uniform cords,from umbo up to edges ( Fig.39A,B,D,E View Figure 39 );interspaces equivalent to each cord width. Periostracum heavy, brown ( Fig. 39 View Figure 39 A-E); when absent, color white ( Fig. 39J, L View Figure 39 ). Ligament with inner portion thick, guttiform, restricted to sub-umbonal region, angulation ~30° in relation to dorso-ventral axis ( Fig. 39F View Figure 39 , G-I, K, M). Hinge occupying entire dorsal edge ( Fig. 39F, G, K, M View Figure 39 ), thicker regions occupying ~15% of shell height; teeth reaching ligamental area; from this region both anterior and posterior series of teeth gradually growing towards edges, becoming wider in subterminal region in both sides, mainly in anterior set, with very broad subterminal stretch; 11-12 teeth in slightly curved, longer anterior set; 8-9 teeth in slightly shorter, also weakly curved posterior set. Both set of teeth with very tall, triangular, pointed teeth ( Fig. 39H, I View Figure 39 ). Both adductor muscle scars rounded, located ventrally to both ends of hinge, anterior scar slightly larger ( Fig. 39G View Figure 39 ); pallial line weakly visible parallel to ventral edge ( Fig. 39G, K View Figure 39 ).

Etymology: The specific epithet is based on the Guarani language word ipepo, meaning wing, an allusion to the expansions in both sides of the umbo.

Distribution: Off Espírito Santo, continental slope of Abrolhos.