Ischnochiton loureiroi, Dell'Angelo, Landau, C. M. D. Silva & Sosso, 2022

Ischnochiton loureiroi View in CoL Dell’Angelo, Landau, Silva & Sosso, 2022

Fig. 66 View FIGURE 66

Ischnochiton loureiroi View in CoL Dell’Angelo, Landau, Silva & Sosso, 2022, p. 10, figs 7.1–7.6.

Type material. Holotype RGM 1364007, intermediate valve, width 3.4 mm ( Figs 66A–C View FIGURE 66 ). Paratype RGM 1364008, intermediate valve ( Figs 66D–E View FIGURE 66 ).

Type locality. Vale de Freixo site, near the village of Carnide, Pombal municipality (central-west Portugal) .

Type stage. Pliocene ( upper Zanclean to lower Piacenzian), Carnide Sandstone Formation .

Material examined. Pliocene: Portugal: Vale de Freixo : type material plus one intermediate valve (width 3.8 mm, valve lost, Figs 66F–H View FIGURE 66 ) .

Description. Head and tail valves unknown. Intermediate valves broadly rectangular, width four times length or a little more (W/L = 4.00–4.10), slightly elevated (H/W = 0.20–0.24), carinate in anterior profile, anterior margin straight, side margins rounded, posterior margin straight on both sides of prominent apex, lateral areas poorly elevated, sharply delimited,

Tegmentum with microgranulose sculpture. LA sculptured with 3 radiating irregular granulose ribs originating at apex, some ribs splitting towards anterior margin, with scattered elevated granules irregularly distributed on striae. CA sculptured with longitudinal irregular granulose ribs (9–11 on each side), with granules coalescent forming uninterrupted ribs, interstices smooth, equal in width to ribs, ribs not reaching anterior margin near JA, large smooth triangular JA, weak growth lines.

Articulamentum with large, triangular apophyses, insertion plate short with a single slit, slit rays scarcely visible.

Remarks. Ischnochiton loureiroi Dell’Angelo, Landau, Silva & Sosso, 2022 is only known from the original material, based on a few and poorly preserved intermediate valves from the Pliocene of Portugal, but the sculpture of the valves is different from that of any other Ischnochiton spp. recorded from the European Neogene.

Comparisons. The only other species with a carinated profile, among the Ischnochiton spp. with granulose ribs from the NE Atlantic area discussed here, are I. zbyi Dell’Angelo & Silva, 2003 and I. renardi Dell’Angelo, Lesport, Cluzaud & Sosso, 2018. Ischnochiton loureiroi markedly differs from I. zbyi by the shape and the different sculpture of the intermediate valves, and from I. renardi by the different sculpture of CA and LA (see Tab. 9).

Distribution. Lower to upper Pliocene: northeastern Atlantic, Mondego Basin, Portugal: Vale de Freixo

( Dell’Angelo et al. 2022).