Leptolepis steberae, Schwarzhans & Keupp, 2022

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 steberae sp. nov.

Plate 2, figs 8-12

Etymology.

Named after Birgit Steber (Leibersdorf), who has intensely collected from the Buttenheim clay pit and provided specimens of this species which were instrumental for its recognition.

Holotype.

SNSB-BSPG 2022 IV 13 (Plate 2 , fig. 8), Clay pit near Buttenheim, upper Pliensbachian, Hawkerense subzone, EPH horizon.

Paratypes.

9 specimens same data as holotype (SNSB-BSPG 2022 IV 14, Plate 2 , figs 9-12).

Diagnosis.

OL:OH = 1.1-1.25. Rostrum short, its length 12-25% of OL. Ventral and dorsal rims regularly curving. Ventral rim of ostium shallow, often fading, no or very weak distinction of ostium and cauda.

Description.

Nearly round, thin otoliths up to 2.5 mm in length (holotype 2.2 mm); OH:OT = 3.5-4.5. Ventral rim deeply and regularly curved, and smooth or intensely and finely crenulated. Rostrum short, blunt. Dorsal rim behind ostial relatively long, elevated, rounded, broad and irregularly undulating. Posterior rim broadly rounded.

Inner face distinctly bent with slightly supramedian sulcus. Ostium short, indistinctly separated from cauda, slightly expanding backward from rostrum and antirostral notch, about as long as cauda. Ventral margin of sulcus often indistinct, gradual, relatively straight with no or very feeble indication of differentiation into ostium and cauda. Cauda straight, terminating close to posterior tip of otolith. Dorsal depression very small, restricted to position above anterior part of cauda. No ventral furrow. Outer face flat to slightly concave, with many short radial furrows particularly along ventral margin of otolith. No or very feeble postcentral umbo.

Discussion.

Leptolepis steberae is a relatively rare and small species in the late Pliensbachian of Buttenheim. It is recognized by its compressed, rounded outline with only a moderately projecting and rather blunt rostrum. Its OL:OH ratio is less than in contemporaneous congeners (1.1-1.25 vs. 1.25-175). The rostrum is shorter than in coeval Leptolepis species (12-25% of OL vs. 30-45%). Another typical characteristic is the nearly straight ventral margin of the sulcus, which is also often rather gradational.

Figures

Plate 2. Otoliths of Leptolepis buttenheimensis and L. steberae. figs 1 - 7 Leptolepis buttenheimensis sp. nov. from the late Pliensbachian of Buttenheim; 1: holotype SNSB-BSPG 2022 IV 4, EPH horizon; 2 - 7: paratypes SNSB-BSPG 2022 IV 5 - 6; 2 - 5, 7: EPH horizon; 6: Apyrenum subzone. figs 8 - 12: Leptolepis steberae sp. nov. from the Pliensbachian of Buttenheim, EPH horizon; 8: holotype SNSB-BSPG 2022 IV 13; 9 - 12: paratypes SNSB-BSPG 2022 IV 14.