Hanleya sossoi, Dell'Angelo, Landau, Van Dingenen & Ceulemans, 2018

Hanleya sossoi View in CoL Dell’Angelo, Landau, Van Dingenen & Ceulemans, 2018

Fig. 49 View FIGURE 49

Hanleya sossoi View in CoL Dell’Angelo, Landau, Van Dingenen & Ceulemans, 2018b, p. 23, fig. 12; Dell’Angelo et al. 2020b, p. 52, tab. 9.

Type material. Holotype MNHN.F.A67088, intermediate valve, width 4 mm ( Figs 49A–D View FIGURE 49 ) . Paratypes: MNHN. F.A67089–A67091 (3 valves, Figs 49E–G View FIGURE 49 ); NHMW 2017/0108/0016–0018 (3 valves); RGM.1008404–1008405 (2 valves) .

Type locality. Saint-Clément-de-la-Place ( France) .

Type stage. Miocene (Tortonian).

Material examined. Miocene (Tortonian): France: Saint-Clément-de-la-Place: type material plus 110 valves ( MNHN.F.A67092, Fig. 49H View FIGURE 49 , MNHN.F.A67093, NHMW 2017/0108/0019, RGM.1008351, RGM.1008406, RGM.1008431, BD 139 ), Sceaux d’Anjou, La Presselière: 1 valve ( RGM.1008446), Beugnon: 1 valve ( RGM.1310178). Maximum width of the valves: 6.1 / 6 / 7.3 mm .

Description. Head valve subovate, posterior margin widely V-shaped. Intermediate valves polygonal, width about twice length (W/L = 1.92–2.03), carinate in anterior profile, moderately elevated (H/W = 0.38), posterior margin with small projecting apex, both sides slightly concave, lateral areas not elevated. Tail valve from elliptical to circular (W/L = 1.31–1.47), anterior margin convex, posterior margin rounded, mucro central, strongly elevated, prominent, antemucronal slope slightly convex, postmucronal slope decidedly concave directly behind mucro, straightening near posterior margin.

Tegmentum surface smooth, granules more spaced from each other, there are no aesthetes among granules. HV, LA and PMA uniformly sculptured with roundish to elongate granules, arranged without pattern, roundish in HV (diameter ca. 100 μm towards margin, progressively smaller towards apex), roundish to slightly elongate in PMA (up to 140 μm long), elongate in LA (up to 130 μm long). CA and AMA with slight radial depression, sculptured with elongate, elevated granules irregularly arranged, but giving the impression of a very irregular longitudinal arrangement, more oblique towards lateral areas, up to 175 μm long in CA, up to 220 μm long in AMA. Variable number of megalaesthetes and microaesthetes, all of same size, up to 30–35 irregularly disposed in CA, 3–5 megalaesthetes in central position and up to 20–25 microaesthetes or more irregularly disposed along margin in AMA, 20 or more irregularly distributed in HV, 10–15 in LA, 2–4 megalaesthetes in central position and up to 12 microasthetes irregularly disposed along margin in PMA; all aesthetes of same size, no aesthetes among granules.

Articulamentum solid, apophyses wide, long, connected to primordium of insertion plates in intermediate valves, insertion plates well developed both on head and tail valves, pectinated on tail valve, muscle scars particularly prominent on tail valves.

Remarks. The fossil record of Hanleya sossoi Dell’Angelo, Landau, Van Dingenen & Ceulemans, 2018 is limited to the Miocene (Tortonian) of the northwestern France. The material from the Miocene (Tortonian) of Saint-Clément-de-la-Place consists mostly of incomplete and poorly preserved valves, especially the characters of the articulamentum are sometimes scarcely visible. The shape and size of the granules is variable on the different areas of the valves, but are similar in PA and JA of intermediate and tail valves. The number and position of microaesthetes is also variable.

Comparisons. Hanleya sossoi can be compared with the other Hanleya spp . with a tegmental sculpture characterized by granules irregularly arranged without pattern ( H. mediterranea Sirenko, 2014 , H. schwabei Dell’Angelo, Sosso & Taviani, 2024, and H. sirenkoi sp. nov.). Hanleya sossoi is the species that has larger (up to 220 μm long) and more spaced from each other granules, and also the greatest number of aesthetes (up to 30–35).

Distribution. Upper Miocene: northeastern Atlantic (Tortonian): Ligerian Basin, France: Beugnon, Saint-Clément-de-la-Place, Sceaux d’Anjou, La Presselière ( Dell’Angelo et al. 2018b).