Leptolepis curvisulcatus ( Schroeder , 1956)

Schwarzhans, Werner & Keupp, Helmut, 2022, Early teleost otolith morphogenesis observed in the Jurassic of Franconia, Bavaria, southern Germany, Zitteliana 96, pp. 51-67 : 51

Leptolepis curvisulcatus ( Schroeder, 1956)

Plate 1, figs 15-19

Otolithus curvisulcatus 1956 Otolithus curvisulcatus - Schröder: pl. 7, figs 25-27.

Otolithus opalini 1956 Otolithus opalini - Schröder: pl. 6, figs 7-8 (non fig. 9).

Otolithus schattenbergi 1956 Otolithus schattenbergi - Schröder: pl. 6, figs 10-12.

Leptolepis ornatus 2018 Leptolepis ornatus (Weiler, 1953) - Schwarzhans: fig. 1I-J, ?K.

Material.

15 specimens from Schröder’s collection from the late Toarcian to early Aalenian: holotype of Ot. curvisulcatus from Kremmeldorf (SNSB-BSPG 2022 III 42, Plate 1 , fig. 16) and 3 paratypes of Ot. curvisulcatus , thereof 2 from Kremmeldorf and 1 from Freiahorn (SNSB-BSPG 2022 III 43-45), holotype of Ot. opalini from Kremmeldorf (SNSB-BSPG 2022 III 16, Plate 1 , fig. 19) and 3 paratypes of Ot. opalini from Kremmeldorf (SNSB-BSPG 2022 III 17-19, Plate 1 , fig. 15), holotype of Ot. schattenbergi from Kremmelsdorf (SNSB-BSPG 2022 III 2, Plate 1 , fig. 17), 6 paratypes of Ot. schattenbergi with 5 from Kremmelsdorf (SNSB-BSPG 2022 III 3-5, 47-48, Plate 1 , fig. 18) and 1 from Peulendorf (SNSB-BSPG 2022 III 46).

Differential diagnosis.

Leptolepis curvisulcatus is slightly more elongate than L. normandica with an OL:OH ratio of 1.4-1.6 (vs. 1.25-1.45), which is mainly caused by a relatively low postdorsal rim, which is also more rounded. Other proportions and characteristics are shared with L. normandica . Leptolepis curvisulcatus also differs from L. normandica in its longer ostium as compared to the length of its cauda, but because of the gradual transition from ostium to cauda, this feature cannot be measured unequivocally. The rounded and short postdorsal rim distinguishes L. curvisulcatus from the coeval L. kremmeldorfensis .

Discussion.

The distinctions among the three nominal late Toarcian to Aalenian species L. normandica , L. curvisulcatus , and L. kremmeldorfensis are all very subtle and it is possible that with more material becoming available from this time interval their nature and validity may have to be revised again. This is also because most specimens so far known from L. curvisulcatus and L. kremmeldorfensis are smaller than 1.5 mm in length and, therefore, cannot be considered morphologically mature. Schröder (1956) mentioned that the slightly curved shape of the sulcus (cauda) is a distinctive character of the species (hence the name curvisulcatus). However, this character does not seem to be reliable for its distinction from otoliths of L. normandica , and we therefore consider it to reflect a degree of variability.

The best-preserved and largest specimen that we attribute to L. curvisulcatus is a paratype of Schröder’s Otolithus opalini of 2.55 mm in length (Plate 1 , fig. 16), while the specimen selected as holotype represents a small and poorly preserved otolith of 1.25 mm in length (Plate 1 , fig. 19). The holotype of L. curvisulcatus is the next best-preserved specimen of 2.25 mm in length, and we have thus chosen this name to represent this nominal species. Schwarzhans (2018) could not review Schröder’s specimens and attributed similar specimens from the same stratigraphic interval to L. ornatus (Weiler, 1953). Unfortunately, Weiler’s type-material has not been located and is not available for revision. His documentation is rather indistinct, so we therefore propose no longer using this name and instead refer to L. curvisulcatus .

Figures

Plate 1. Otoliths of Leptolepis normandica and L. curvisulcatus. figs 1 - 15: Leptolepis normandica Nybelin, 1962; 1 - 11: From late Pliensbachian of Buttenheim, 1 - 8, 11: EPH horizon (SNSB-BSPG 2022 IV 3); 9: " Quellhorizon " (SNSB-BSPG 2022 IV 2); 10: Apyrenum subzone (SNSB-BSPG 2022 IV 1); 12: paratype of Ot. cristatus Schroeder, 1956 from Kremmeldorf (SNSB-BSPG 2022 III 5); 13: paratype of Ot. opalini Schroeder, 1956 from Kremmeldorf (SNSB-BSPG 2022 III 20); 14: paratype of Ot. vastus Schroeder, 1956 from Kremmelsdorf (SNSB-BSPG 2022 III 34); 15: holotype of Ot. vastus from Peulendorf (SNSB-BSPG 2022 III 30). figs 15 - 19 Leptolepis curvisulcatus (Schroeder, 1956); 15: paratype of Ot. opalini Schroeder, 1956 from Kremmeldorf (SNSB-BSPG 2022 III 17); 16: holotype of Ot. curvisulcatus Schroeder, 1956 from Kremmeldorf (SNSB-BSPG 2022 III 42); 17: holotype of Ot. schattenbergi Schroeder, 1956 from Kremmelsdorf (SNSB-BSPG 2022 III 2); 18: paratype of Ot. schattenbergi Schroeder, 1956 from Kremmelsdorf (SNSB-BSPG 2022 III 47); 19: holotype of Ot. opalini Schroeder, 1956 from Kremmeldorf (SNSB-BSPG 2022 III 16).