Leptochiton rumani, Dell’Angelo & Sosso & Taviani, 2025

Leptochiton rumani sp. nov.

Fig. 30 View FIGURE 30

Leptochiton sp. Ruman & Hudáčková, 2015, p. 158, figs 3.2–3.6.

Type material. Holotype MSNG 62633 View Materials , intermediate valve, width 1.5 mm ( Figs 30E–G View FIGURE 30 ) . Paratype 1, MSNG 62633 View Materials , head valve from Rohožnik, width 1.5 mm ( Figs 30A–B View FIGURE 30 ) . Paratype 2, SNM Z38496/a (as Leptochiton sp. ), tail valve from Rohožnik, width 1.1 mm ( Fig. 30H View FIGURE 30 ).

Type locality. Devínska Nová Ves ( Slovenia) .

Type stage. Middle Miocene.

Etymology. The name honors Andrej Ruman (Comenius University, Bratislava, Slovakia) for his contribution to the study of fossil mollusks.

Material examined. Middle Miocene: Central Paratethys : Slovakia: Devínska Nová Ves brickyard: holotype plus 1 valve ( BD 403 ; Rohožnik–konopiská clay pit (“Hornáčková jama”): paratype plus 6 valves ( BD 404 , Figs 30C–D View FIGURE 30 ). Maximum width of valves: 1.5 mm.

Diagnosis. Valves fragile and small, head valve semicircular, intermediate valves broadly rectangular, rounded, elevated, apex inconspicuous, tail valve elliptical, mucro not prominent, in anterior position. Tegmentum surface rough, sculptured with roundish granules, arranged without pattern in HV, elliptical, narrow granules, concentrically arranged in LA, PMA, roundish granules, arranged without pattern, with generally one or two stems in apical part in CA, AMA, each granule with up to 4–5 aesthetes almost aligned in HV, LA, up to 5–7 aesthetes in CA, all more or less of same size.

Description. Valves fragile and of small size. Head valve semicircular. Intermediate valves broadly rectangular (W/L = 1.91–2.18), rounded in anterior profile, elevated (H/W = 0.51 estimated), anterior margin straight, side margins rounded, posterior margin almost straight, apex inconspicuous, lateral area slightly raised, with few concentric growth marks. Tail valve elliptical, anterior margin convex, mucro not prominent, in anterior position, without any distinct diagonal ridge.

Tegmentum surface rough, very dense but well separated granules. HV sculptured with roundish granules arranged without pattern, diameter 30–40 µm. LA and PMA sculptured with elliptical, narrow granules, concentrically arranged, long 30–40 µm. CA and AMA sculptured with roundish/polygonal granules very irregular, arranged without pattern, with generally one or two stems (or at least a hint of) in apical part, up to 65 µm long. Each granule with up to 4–5 aesthetes almost aligned in HV and LA, up to 5–7 aesthetes, both on top and peripheral margin in CA, all aesthetes more or less of same size.

Articulamentum without insertion laminae, with small apophyses, widely separated.

Remarks. The fossil record of Leptochiton rumani sp. nov. is limited to the Middle Miocene of Slovakia. This species has already been reported and figured by Ruman & Hudáčková (2015), as Leptochiton sp.

Despite the small size of the valves examined, often incomplete, the sculpture of the valves of Leptochiton rumani sp. nov. is different from that of the other species known from the Paratethys [( L. boettgeri ( Šulc, 1934) , L. sulci ( Bałuk, 1971) and L. cancellatus ( Sowerby, 1840) ], all characterized by the presence of granules arranged in radial series on HV, LA and PMA, and in longitudinal series on CA and AMA (see above and tab. 4b). Notwithstanding the incompletness of the holotype, we have estimated the dorsal elevation H/W (put in brackets in tab. 4).

The granules have a very irregular structure, even aesthetes are hardly divisible in megalaesthetes and micraesthetes. In some granules the size of the pores of the aesthetes located centrally seem slightly larger than the others, but this could be due to erosion, for which we rate aesthetes more or less of the same size.

Comparisons. The characteristics of the sculpture of Leptochiton rumani sp. nov. support its belonging to the Leptochiton tavianii group, see Tab. 4. However, all these species present a different tegmentum sculpture than the species here under study.

Distribution. Middle Miocene: Central Paratethys (Langhian-Serravallian): Slovakia: Devínska Nová Ves, Rohožník ( Ruman & Hudáčková 2015; this study).