Neoopisthopterus weltoni, 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 : 42-43

Neoopisthopterus weltoni sp. nov.

urn:lsid:zoobank.org:act:023E1875-E9C9-4E5A-A087-E1F1DF4FF1C4

Fig. 13E–F

Diagnosis

OL/OH = 1.64–1.68, OsL/CaL = 1.00–1.07. Otoliths trapezoid, thin, with large rostrum. Sulcus wide and shallow. Ostium opens widely. Cauda straight and wide.

Etymology

This species is dedicated to Bruce Welton, who provided us a lot of otoliths, and as an appreciation of his extensive work on the fossil shark teeth from the Gulf Coast area.

Material examined

Holotype UNITED STATES OF AMERICA • Left otolith; Texas, Crockett; Landrum Member of the Cook Mountain Formation ; Fig. 13E ; IRSNB P 10018 .

Paratypes UNITED STATES OF AMERICA • 2 otoliths, of which one is figured: Fig. 13F ; Texas, Stone City Bluff, Brazos River ; “ Stone City beds”; IRSNB P 10019 .

Type locality and horizon

United States of America, Crockett (Texas), Landrum Member of the Cook Mountain Formation.

Dimensions of the holotype

Length = 1.13 mm; height = 0.94 mm; thickness = 0.32 mm.

Description

This species is characterized by rectangular to trapezoid otoliths. The dorsal rim is more or less straight. The posterior rim is gently curved, forming rounded junctions with the dorsal and ventral rims. The ventral rim varies, which partly resulted from its preservation status; it is slightly irregular in the holotype ( Fig. 13E ), but largely undulated in the figured paratype. The anterior portion is characterized by a large, robust, and extended rostrum with a small but notable excisura. The otoliths are nearly flat on both faces. The sulcus is not deep but very wide and clearly divided into ostium and cauda. No collicula are visible. The ostial crista inferior curves somewhat upwards anteriorly and the ostium opens widely antero-dorsally. The cauda is straight and wide. At its posterior end, the cristae are indistinct. The dorsal area is somewhat hollowed out.

Remarks

Neoopisthopterus weltoni sp. nov. is a rare species; only three specimens are currently known: two from the Cook Mountain Formation and one from the “Stone City beds”, both in Texas. The above diagnosis allows us to assign this new species to the Recent genus Neoopisthopterus (see Nolf & Aguilera 1998: pl. 2 fig. 11 for an illustration of an otolith of the Recent N. tropicus ).

Stratigraphic and geographic distribution

Lutetian: “Stone City beds”, Texas. Bartonian: Landrum Member, Texas.

Figures

Fig. 13. Fish otoliths from the US middle and upper Eocene. A–C. “Conger” websteri (Frost, 1933), Piney Point F., Pamunkey River, 1 km E of Eanes property, Virginia (IRSNB P 10014–10016). D. “Osteoglossum” aff. rhomboidalis (Stinton, 1977), “Stone City beds”, Stone City Bluff, Brazos River, sample 2 from bed P, Texas (P 10017). E–F. Neoopisthopterus weltoni sp. nov. E. Landrum M., Crockett, Texas, holotype (IRSNB P 10018). F. “Stone City beds”, Stone City Bluff, Brazos River, bed I, Texas, paratype (IRSNB P 10019). G. Sardinops sp., Landrum M., Crockett, Texas (IRSNB P 10020). H. Clupeidae indet., Landrum M., Crockett, Texas (IRSNB P 10021). I–J. Plotosus sp., Wheelock M., Little Brazos River, confluence with Brazos River, Texas (P 10022–10023). 1 = ventral view; 2 = inner view; 3 = anterior view. Scale bars = 1 mm.