Sciaena? radians ( Koken, 1888 )

Sciaena? radians ( Koken, 1888)

Fig. 26 View Fig BB–CC

Otolithus (Sciaenidarum) radians Koken, 1888: 280 .

Material examined

UNITED STATES OF AMERICA – Mississippi • 3 sagittae; Catahoula Formation ; MMNS VP-8934 , MMNS VP-12076 ( Fig. 26 View Fig BB–CC), SC 2013.28.763 .

Description

The outline of the sagitta is somewhat rectangular (sensu Smale et al. 1995), but the anterior, dorsal, and ventral margins are slightly convex and rounded to various degrees ( Fig. 26 View Fig BB). The margins are typically smooth, and there is a highly characteristic inframedian tip on the posterior margin. The inner face is moderately convex ( Fig. 26 View Fig CC) and characterized by a very large and prominent heterosulcoid-type sulcus. The ostium is noticeably large in its length and height. The ostium extends from near the anterodorsal margin well into the ventral field and is largest at the posterior portion. The ventral margin of the ostium curves distinctly upward toward the anterior margin and is subparallel to the anteroventral margin. The posteroventral portion of the ostium extends conspicuously underneath the cauda, especially on larger specimens. The height of the cauda is about 30% of the height of the ostium. The cauda has a characteristic horizontal and downturned component. The horizontal and downturned portions are of similar length, but the downturned portion is usually slightly longer on the larger specimens ( Nolf 2003: pl. 4 figs 1–3). The outer face becomes somewhat more irregular on larger specimens. The outer face is nearly flat on small specimens but is more convex on larger specimens, although it is not nearly as convex as the inner face.

Remarks

Koken (1888) originally named Otolithus (Sciaenidarum) gemma based on specimens labeled only as “Vicksburg” from Mississippi, USA. Unfortunately, Koken’s type suite actually contained three different species, including Sciaena? radians , S.? pseudoradians , and Aplodinotus gemma (see discussion in Nolf 2003). Only three specimens of Sciaena? radians were recovered from the Catahoula Formation (less than 1% of the total specimens), and the species is the least common of the sciaenids within the otolith assemblage. Although “ S.? ” radians is widespread in the Gulf Coastal Plain and is known from many Oligocene formations in Mississippi, Louisiana, and Alabama ( Nolf 2003, 2013; Stringer & Worley 2003; Worley 2004; Stringer et al. 2020c), the species is similarly rare in those assemblages.