Pterothrissus umbonatus

Pterothrissus umbonatus (Koken, 1884)

Fig. 8I–L

Otolithus (incertae sedis) umbonatus Koken, 1884: 557, pl. 12 fig. 12.

Otolithus (inc. sedis) aff. umbonato – Koken 1888: 294, pl. 17 fig. 12a.

Pterothrissus umbonatus – Weiler 1958: 325, pl. 1 fig. 1. — Nolf 1985: 40 fig. 35d; 2013: 33, pl. 15.

Pterothrissus sp. – Nolf & Stringer 2003: pl. 1 fig. 1.

Remarks

The otoliths of P. umbonatus are characterized by a large and elliptic ostium and nearly straight cauda, typical of Pterothrissus. These otoliths show a marked ontogenetic change in the development of the ventral area, whose anterior part becomes much deeper in larger specimens. The species can be found in all regions studied here, but is more abundant at the Texas localities (Table 1). In particular, we note that the species also comprised a significant percentage (over 13%) of the Cane River Formation (Louisiana) otolith assemblage (Stringer & Breard 1997). The otoliths show little difference both in time and space. They have a remarkable distribution ranging in age from the middle Eocene to the middle Miocene (Schwarzhans 2010) and can be found at both European and North American localities.

Stratigraphic and geographic distribution

Lutetian: Weches Formation and “Stone City beds”, Texas; Cane River Formation, Louisiana; Piney Point Formation, Virginia. Bartonian: Cook Mountain Formation, Texas and Mississippi; “upper” Lisbon Formation, Alabama. Priabonian: Yazoo Clay, Louisiana and Mississippi. In Europe, the species is known from the Lutetian till the end of the Oligocene.