Sanyuania sp.

Figs 14, 15, 16

Material.

Single male specimen; BA19005-8.

Dimensions.

L = 245 μm, H = 116 μm, W ≈ 120 μm .

Description.

Carapace (Figs 14A-E, 16A, C) small subtriangular shape in lateral view. Greatest height at ¼ of length. Anterior margin broadly rounded. Posterior margin narrowly rounded. Dorsal margin straight, moderately sloping down from the greatest height to the posterior margin. Ventral margin straight in middle part in both valves, with slightly concave regions in the very middle, forming distinct flaps as an area of valve overlap (LV>RV) (Fig. 16A). From posterior third, ventral margin ascending towards posterior end. Carapace in dorsal view elliptical, with posterior and anterior part compressed and central region strongly protruding. The valve’s lateral surface punctate in the flat anterior and posterior marginal regions, while pitted (i.e., covered with wider and deeper depressions) in the central region and dorsally. Valves thick in cross section (Fig. 16C). Inflated central region with distinct sulcus mid-dorsally. Inner calcified lamella wide. Central muscular scar pattern, pore morphology and detailed hinge elements not preserved.

Soft parts almost all preserved, but with a low degree of detail.

A1 (Figs 14F, G, 15A, 16D) rod-shaped. Segmentation and setation not preserved.

A2 (Figs 14H, I, 15B, 16D) more robust than A1, number of segments unknown. With prominent knee between protopodite and endopodite, close to which the spinneret seta (exopodite) originates, the only preserved setation of both A2 in this specimen.

Between the right A2 and the internal side of RV, a roundish, disk-shaped body is preserved, which we tentatively interpret as the sac of the spinneret gland containing the secretion (Fig. 16D).

Md (Figs 14J, K, 15E, 16B, E) Masticatory process of coxa preserved, reaching into the oral opening, but teeth only weakly preserved. The palp’s segmentation and setation not preserved. Vibratory plate not preserved.

Mxl (Figs 14L, M, 15C, 16B) Protopod with three masticatory lobes (endites 1-3) and two-segmented palp, without any claws/setae preserved; branchial plate preserved.

L5 (Figs 14N, O, 15F, 16F) Walking leg, elongate, with long endopodite consisting of indeterminate number of segments.

L6 (Figs 14P, Q, 15G, 16F) Presumed walking leg, protopodite elongate, endopod not well preserved.

L7 (Figs 14R, 15H) Walking leg, elongate protopodite and long endopodite, the latter with at least three segments.

HP (Figs 15D, 16F, G) almost triangular in shape, apically forming distinct tip, shaped like an arrowhead.

Remarks.

We assign the studied specimen to the genus Sanyuania within the Loxoconchidae, mainly based on shape, ornamentation and morphology of its carapace. Preserved soft parts, although with little detail, and without genus-specific features being observable, at least do not oppose this assignment. The morphology of the preserved hemipenes is clearly in line with Hartmann’s (1966: 758) description of hemipenes typical of Loxoconchinae as consisting of a voluminous capsule and a triangular, distally rounded top piece. A direct comparison of our specimens’ hemipenis with that of Sanyuania segersi Savatenalinton & Martens, 2009a shows a high degree of similarity (Savatenalinton and Martens 2009a: fig. 5A) with its triangular (arrow-head-like) distal tip on a broad, rounded main body. Regarding the shape of the carapace, as well as the flattened anterior and posterior margins, our specimen is most similar to S. cuneata Zhao & Whatley, 1992. However, the surface ornamentation of the valves with broader pits centrally and smaller ones marginally, comes closer to that of S. wangi Zhao & Whatley, 1992. None of the known Sanyuania species, however, possess the mid-dorsal sulcus featured in our specimen. Clearly our data on this single specimen are too limited for more certainty; more specimens are needed for a full taxonomic assessment. We therefore present this specimen in open nomenclature here.