Parascombrops yanceyi, Lin & Nolf & Steurbaut, 2022

Lin, Chien-Hsiang & Nolf, Dirk, 2022, Middle and late Eocene fish otoliths from the eastern and southern USA, European Journal of Taxonomy 814, pp. 1-122 : 75-77

Parascombrops yanceyi sp. nov.

urn:lsid:zoobank.org:act:12B10CEA-D774-4789-98B9-4A425D01D565

Fig. 26

Diagnosis

OL/OH = 1.71–1.94, OsL/CaL = 0.77–1.00. Elongate otoliths with large rostrum and blunt posterior rim. Oval ostium with oblong colliculum. Elongate and narrow cauda of over ½ OL, with crest-like crista superior.

Etymology

This species is dedicated to Thomas Yancey for his much appreciated support during our field work in the Brazos River area.

Material examined

Holotype UNITED STATES OF AMERICA • Left otolith; Texas, Alabama Ferry; “ Stone City Beds ”; Fig. 26A ; IRSNB P 10157 .

Paratypes UNITED STATES OF AMERICA • 11 otoliths, of which one is figured: Fig. 26B ; Texas, Little Brazos River, confluence with Brazos River; Wheelock Member ; IRSNB P 10158 • 66 otoliths, of which six are figured: Fig. 26C–H ; Texas, Stone City Bluff; “ Stone City beds”; IRSNB P 10159–10164 • 6 otoliths; Texas, Pin Oak Creek; Landrum Member .

Type locality and horizon

United States of America, Alabama Ferry (Texas), “Stone City beds”.

Dimensions of the holotype

Length = 6.85 mm; height = 3.85 mm; thickness = 1.01 mm.

Description

This species is characterized by elongated otoliths with a well-marked rostrum and a more blunt posterior end. The dorsal rim bears a marked postero-dorsal angle and a subtle antero-dorsal angle which is located at a slightly raised part of the dorsal rim. The ventral rim is smoothly curved with its deepest part in the middle, or slightly to the anterior part of the otolith. The posterior rim is oblique after the posterior-dorsal angle and provides a sharp to nearly vertical posterior end to the otolith. The anterior rim looks triangular, with a pointed tip which forms an evident rostrum. The margins of the otoliths vary: they are smooth in larger specimens, and lobed in juveniles. The otoliths are thin; the inner face is convex and the outer face is slightly concave. The sulcus is well-developed and moderately incised, with a wide and oblong ostium and long and narrow cauda. The ostium opens widely on the antero-dorsal side and is completely filled with a colliculum. The cauda is straight for about two-thirds of its length, and its posterior part is bent in a ventral direction. The cristae are well-developed and near the collum, the crista superior is ridge-like. The ostial crista superior curves towards the dorsal rim. The ventral area is wide and has about the same height as the dorsal one.

Remarks

The shape of the otoliths of the species demonstrate some similarities to those of moronids, but the relatively flat inner face, shorter cauda and slightly upwards oriented ostium strongly suggest that this species must be an acropomatid. A critical review on the taxonomy and the otoliths of acropomatids is provided by Schwarzhans & Prokofiev (2017), in which they also stated that fossil otoliths of acropomatids may have been more widely distributed.

Stratigraphic and geographic distribution

Lutetian: “Stone City beds”, Texas. Bartonian: Cook Mountain Formation, Texas.

Figures

Fig. 26. Otoliths of Parascombrops yanceyi sp. nov. from the US middle and upper Eocene. A. “Stone City beds”, Alabama Ferry, on Trinity River, North, Texas, holotype (IRSNB P 10157). B. Wheelock M., Little Brazos River, confluence with Brazos River, Texas, paratype (IRSNB P 10158). C–H. “Stone City beds”, Stone City Bluff, Brazos River, Texas, paratypes (IRSNB P 10159–10164). C–D. Sample 5 from bed S (IRSNB P 10159–10160). E–H. Bed P (IRSNB P 10161–10164). 1 = ventral view; 2 = inner view. Scale bars = 1 mm.