Sciaenidae

Schwarzhans, Werner W., Aguilera, Orangel A., Scheyer, Torsten M. & Carrillo-Briceño, Jorge D., 2022, Fish otoliths from the middle Miocene Pebas Formation of the Peruvian Amazon, Swiss Journal of Palaeontology (2) 141 (1), pp. 1-15 : 7-9

Family Sciaenidae

Te morphometric measurements in the following descriptions of sciaenid otoliths follow that established in Aguilera et al. (2016).

Genus Pebasciaena n. gen.

Type species: Pebasciaena amazonensis n. sp.

Etymology. Combination of the formation name Pebas and the Pebas Wetland System with the type genus name Sciaena .

Diagnosis. An otolith-based genus of the family Sciaenidae with a typical sciaenid-type sulcus characterized by a wide and shallow ostium and a steeply curved, narrow, and somewhat deepened cauda. Morphometric key ratios: OL:OH = 1.35, OsL:OsH = 1.15; caudal curvature index = 0.7; ostial–caudal interspace = 23% of SuL. Ostium with distinct postostial lobe and predorsal depression. Vertical section of cauda bent forward at its lower portion. Ventral rim with midventral angle. No distinct umbo on outer face.

Discussion. Pebasciaena shows a highly diagnostic otolith morphology that clearly differs from that of other freshwater sciaenid taxa. For example, it differs from otoliths of Plagioscion in the deep ventral rim, the lack of an umbo on the outer face, and the shape of the very wide ostium with a strong postostial lobe and predorsal depression (vs. spatulate ostium shape). It shares with Pachypops and Pachyurus (see Schwarzhans, 1993 for figures) the lack of an umbo on the outer face, the more deeply curved ventral rim, and the general shape of the ostium but differs in the much larger and wider ostium and the narrower ostial–caudal interspace (23% vs. 35–40% of SuL). Te origin and relationships of the genus are unresolved. It could be related to Pachypops but also shows some resemblance to otoliths of certain marine sciaenids, such as Umbrina , Polycirrhus , and the extinct genus Frizzellithus . Pebasciaena differs from Umbrina and Polycirrhus otoliths in the cauda, which extends much below the limit of the ostium and the shape of the ventral rim. It differs from Frizzellithus in the less compressed shape (OL:OH = 1.35 vs. 1.05–1.15), the less strongly widened ostium, and the slightly larger ostial–caudal interspace (23% vs. 17–22% of SuL). For comparative extant and fossil otoliths of the mentioned genera, see Schwarzhans (1993) and Aguilera et al. (2016).

Species. Established as monospecific genus: Pebasciaena amazonensis n. sp.