Hanleya glimmerodensis Janssen, 1978

Hanleya glimmerodensis Janssen, 1978 View in CoL

Fig. 42 View FIGURE 42

Hanleya glimmerodensis Janssen, 1978, p. 222 View in CoL , pl. 15, figs 28–30; Van Belle 1981, p. 41; Gürs 1995, p. 25; Dell’Angelo et al. 2011, p. 953; Sirenko 2014, p. 2930; Dell’Angelo et al. 2018a, p. 22, figs 4M–U.

Type material. Holotype SMF 250038 About SMF , a tail valve Fig. 42C View FIGURE 42 . Paratypes SMF 250040 About SMF , a head valve Fig. 42A View FIGURE 42 and SMF 250039 About SMF , an intermediate valve Fig. 42B View FIGURE 42 .

Type locality. Höllkopf near Glimmerode ( Germany) .

Type stage. Oligocene (Chattian).

Material examined. Lower Oligocene: France: Gaas (Espibos): 6 valves ( DA, Figs 42D, 42I–L View FIGURE 42 ); Gaas (Lagouarde): 1 valve ( DA). Oligocene, Chattian: Germany: Kassel, Glimmerode: 3 valves ( BD 423, Figs 42E–H View FIGURE 42 ). Maximum width of the valves: 2.2 / 4.7 / 3.7 mm.

Description. Head valve nearly semicircular, highly arched, slightly bent in middle. Intermediate valve broadly rectangular (W/L = 1.72–2.28), semicarinate in anterior profile, moderately elevated (H/W = 0.40–0.48), anterior margin slightly convex, side margins rounded, posterior margin straight with apex not evident, lateral areas not raised, only marked by a difference in sculpture. Tail valve elliptical, mucro subcentral, blunt, clearly highlighted, antemucronal slope slightly convex, postmucronal slope concave.

Tegmentum surface rough. HV, LA and PMA uniformly sculptured with numerous roundish granules, unclearly arranged concentric rows. CA and AMA sculptured with longitudinal striae of roundish to oval granules (ca 10 on each PA, ca 40 in whole CA), straight or slightly obliquely running, finer, more irregular and close set on JA.

Articulamentum with apophyses wide, rounded, widely projecting.

Remarks. The fossil record of Hanleya glimmerodensis Janssen, 1978 is limited to the Oligocene of the Aquitaine Basin (Rupelian) and of the Mainz Basin (Chattian). The only differences highlighted between the valves from Gaas and those from Germany regards the sculpture of tegmentum in JA, well evident in the material from Gaas, more insubstantial or less defined in the material from Germany, and the more elevated intermediate and tail valves from Gaas compared to the German ones (e.g., H/W = 0.43–0.48 vs. 0.40).

Comparisons. This species is similar to Hanleya hanleyi (Bean in Thorpe, 1844) and H. multigranosa ( Reuss, 1860) , with which it shares the same type of tegmental sculpture, and from which it differs by slight differences in the valves shape and by the different geographic and stratigraphic range, from extant Mediterranean Sea and Atlantic Ocean up to the upper Miocene of North Italy for H. hanleyi, Middle Miocene of Paratethys for H. multigranosa , and Oligocene of France and Germany for H. glimmerodensis Janssen, 1978 .

Distribution. Lower Oligocene: northeastern Atlantic (Rupelian): Aquitaine Basin, France: Gaas ( Dell’Angelo et al. 2018a); Upper Oligocene: North Europe: Mainz Basin, Germany: Glimmerode, Freden, Söllingen, Doberg ( Janssen 1978).