Leptochiton uhligi ( Koenen, 1892 )

Leptochiton uhligi ( Koenen, 1892) View in CoL

Fig. 36 View FIGURE 36

Chiton uhligi Koenen, 1892, p. 973 , pl. 59, figs 24a–c, 25a–b.

Lepidopleurus uhligi ; Janssen 1978, p. 217, pl. 14, figs 1–2; Gürs 1995, p. 23, pl. 1, figs 5–7.

Lepidopleurus ( Leptochiton) uhligi ; Dell’Angelo & Palazzi 1989, p. 70, pl. 22, figs 3–4.

Leptochiton uhligi View in CoL ; Van Belle 1981, p. 78; Dell’Angelo et al. 2011, p. 953, Appendix 2.

Type material. Lectotype SMF 250010, designated by Janssen (1978), tail valve figured by Koenen (1892: figs 24a–c) and Janssen (1978: pl. 14, fig. 1), Fig. 36A View FIGURE 36 ; Paralectotype, tail valve figured by Koenen (1892: figs 25a–b).

Type locality. Brandhorst ( Westphalia, Germany) .

Type stage. Lower Oligocene (Rupelian) .

Material examined. No actual material available, only descriptions and illustrations from the literature.

Description. Head valve semicircular, posterior margin widely V-shaped.Intermediate valve broadly rectangular, anterior margin straight, rounded in anterior profile, side margins slightly rounded, posterior margin straight, apex not developed, lateral areas not raised, barely differentiated from central area. Tail valve semicircular, anterior margin straight, mucro in central position, just prominent.

HV and PMA sculptured with radial striae of roundish granules on head valve and postmucronal area of tail valve, LA finely granulated such as to appear almost smooth. CA and AMA sculptured with longitudinal granular striae of roundish granules.

Articulamentum without insertion laminae, apophyses small, widely spaced.

Remarks. The descriptions by Koenen (1892) and Janssen (1978) are based only on intermediate and tail valves. Gürs (1995: pl. 1, fig. 5–7) illustrates three valves ( Figs 36B–D View FIGURE 36 ), also including a head valve ( Fig. 36B View FIGURE 36 ).

Comparisons. The characteristics of the sculpture of Leptochiton uhligi ( Koenen, 1892) agree with the belonging of the species to the Leptochiton cancellatus group, see Tab. 2, albeit with some doubts. The sculpture of lateral areas of intermediate valves is not so clear seeing Fig. 36C View FIGURE 36 , Janssen (1978) reports areas finely granulated such as to appear almost smooth, and this raises some doubts about the presence of radial striae of granules.

Leptochiton uhligi differs from other Leptochiton species by the particularly pronounced central area, the lateral areas barely differentiated, and the mucro of the tail valve just prominent ( Janssen 1978).

Distribution. Lower Oligocene: North Europe, Germany: Böseberg, Brandhorst ( Janssen 1978).

Genus Belknapchiton Sirenko, Saito & Schwabe, 2022

Type species. Leptochiton belknapi Dall, 1878 View in CoL by original designation.

Distribution. Belknapchiton is known from the Pliocene to the Recent. To date there are 22 Recent species known, the vast majority of which inhabit the deep waters of the Pacific Ocean and only B. alveolus (M. Sars MS, Lovén, 1846) is known from the Atlantic Ocean. The fossil record includes the Pliocene to Pleistocene of Italy ( Dell’Angelo et al. 2013, 2021b; Taviani et al. 2023).

Remarks. The genus Belknapchiton was recently established by Sirenko et al. (2022), and contains a widespread group of species conventionally assigned to Leptochiton . The new genus differs from other representatives of the family Leptochitonidae by having an elongate oval shape of body, small rather narrow, sharply pointed scales and scattered long, smooth, needles, the combination of a wide central tooth with short first lateral teeth, and large head of major lateral teeth of radula occasionally with an additional small denticle-like appendage at inner edge.

The main morphological characters of Belknapchiton alveolus are reported in Tab. 5, for ease of comparison with other spp. of Leptochiton showing similar features.