Stenoplax paviai, Dell'Angelo, Giuntelli, Sosso & Zunino, 2014

Stenoplax paviai View in CoL Dell’Angelo, Giuntelli, Sosso & Zunino, 2014

Fig. 72 View FIGURE 72

Stenoplax paviai View in CoL Dell’Angelo, Giuntelli, Sosso & Zunino, 2014, p. 49, pl. 1, figs 1–9; Dell’Angelo et al. 2015a, p. 234, pl. 5, figs 12–17; Dell’Angelo et al. 2016, p. 97; Cherns & Schwabe 2019, p. 8; Dell’Angelo et al. 2018b, p. 29, fig. 15.

Type material. Holotype: MGPT PU 108791 (tail valve) . Paratypes: MGPT PU 108792–108795 : 4 valves ( Fig. 72J View FIGURE 72 ); MSNG 57252 View Materials : 2 valves; ZISP 2199–2200 View Materials : 2 valves; MZB 60085–60087: 3 valves ( Figs 72I, 72K–L View FIGURE 72 ); NHMW 2013/0272/0001: 2 valves .

Type locality. Rio di Bocca d’Asino , Alessandria ( Italy) .

Type stage. Miocene (Tortonian).

Material examined. Middle Miocene (Langhian): Italy: Albugnano : 1 valve ( MZB 32030 ) . Upper Miocene ( Tortonian) : Italy: Borelli : 1 valve ( MGPT PU 135042 ) , Rio di Bocca d’Asino : type material plus 37 valves ( BD 542 , PG, MZB 32031–32032 ) , Villa Monti : 1 valve ( MZB 32052 ) . France: Beugnon : 8 valves ( RGM.1310172, RGM.1310175, RGM.1310179), Renauleau: 5 valves ( BD 144 , MNHN.F.A67107), Saint-Clément-de-la-Place: 347 valves ( BD 143 , MNHN.F.A67103–A67106, Figs. 72A–H View FIGURE 72 , NHMW 2017/0108/0027, RGM.1008353, RGM.1008382, RGM.1008433). Maximum width of the valves: 7 / 8.8 / 5.7 mm .

Description. Head valve semicircular, posterior margin widely V-shaped. Intermediate valves broadly rectangular (W/L = 2.27), moderately elevated (H/W = 0.38), rounded in anterior profile, anterior margin straight between apophyses, side margins rounded, posterior margin about straight, apex not indicated, lateral areas little raised, poorly defined. Tail valve semicircular, depressed (W/L = 1.52–1.66), anterior margin straight, mucro subcentral, weak indicated, antemucronal and postmucronal slopes almost straight.

HV, LA and PMA sculptured with many close-set, irregularly undulate concentric grooves, better defined towards periphery. CA and AMA smooth, with some longitudinal grooves (that continue without interruption concentric grooves) towards the margins, slightly obliquely directed.

Articulamentum with apophyses triangular, widely separated by straight sinus, insertion plates short, slit formula 10–13 / 2 / 14, slit rays neatly indicated by distinct rays of pores, teeth sharp, eaves narrow.

Remarks. Stenoplax paviai Dell’Angelo, Giuntelli, Sosso & Zunino, 2014 was originally described on a few valves from the Miocene (Tortonian) of Rio di Bocca d’Asino, complete intermediate valves were not present, and some important characters were unknown. New and abundant material found in recent years from the Miocene (Tortonian) of Saint-Clément-de-la-Place allowed to complete the description also for the intermediate valves and to better define some specific characters ( Dell’Angelo et al. 2018b). The fossil record was also extended to the Miocene (Langhian) of N. Italy ( Dell’Angelo et al. 2015a).

Comparisons. Stenoplax paviai Dell’Angelo, Giuntelli, Sosso & Zunino, 2014 differs from S. veneta Dell’Angelo & Palazzi, 1992 by the different sculpture, fully covered by small granules in S. veneta . Stenoplax paviai is superficially like Tegulaplax hululensis (E.A. Smith, 1903) , a living species with a widespread distribution in the Indo-Pacific, and also in the Mediterranean coast of Israel, from which it differs by the different shape of the valves, the sculpture CA and AMA, the pectinate teeth ( Kaas et al. 2006).

Distribution. Lower Miocene: Proto–Mediterranean Sea (Langhian): N. Italy: Albugnano ( Dell’Angelo et al. 2015a). Upper Miocene: northeastern Atlantic: Ligerian Basin, France: Beugnon, Renauleau, Saint-Clément-de-la-Place ( Dell’Angelo et al. 2018b); Proto–Mediterranean Sea: Po Basin, N. Italy: Borelli, Rio di Bocca d’Asino, Villa Monti ( Dell’Angelo et al. 2014, 2015a).