Otolithus thevenini, (Priem, 1906)

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 : 27

Muraenanguilla aff. thevenini (Priem, 1906)

Fig. 38H

Otolithus (Trachini) thevenini Priem, 1906: 273 , figs 30–31.

Gymnothorax diagonalis Stinton & Nolf, 1970: 220 , pl. fig. 3.

Muraenanguilla balegemensis Schwarzhans 2019a: 26–27 , fig. 13.13–16.

“genus Congridarum ” aff. diagonalis – Müller 1999: 84, fig. 21/10.

“genus Congridarum ” aff. thevenini – Nolf & Stringer 2003: 5, pl. 2 fig. 15.

Remarks

The fossil genus Muraenanguilla was recently established by Schwarzhans (2019a) for otoliths that were variously attributed to muraenids, congrids and ophichthids and is based on the type species Otolithus (Trachini) thevenini Priem, 1906 . It is known from many European Paleocene and Eocene localities and is probably represented only by a single species in Europe. The taxon was cited often as “genus Congridarum ” diagonalis but was originally described as a muraenid, under the name Gymnothorax diagonalis . It was even considered as possibly belonging to the family Ophichthidae by Nolf & Lapierre (1979: 88). Although the general look of these rather robust otoliths resembles otoliths of congrids, the deep ostium that opens widely on the anterior rim and the crista inferior ending on a little rostrum are not congrid features. Therefore, we agree with Schwarzhans’ solution to consider it as an incertae sedis anguilliform. The holotype of Muraenaguilla thevenini was considered of doubtful quality by Nolf (1985: 132), but the numerous topotypes from Hérouval that are now available leave no doubt about the identity of the holotype ( Nolf 2013). After his discussion on Muraenanguilla, Schwarzhans (2019a) also introduced a new species, M. balegemensis , based on small specimens. These are no more than the juveniles of M. thevenini , and both otolith types are always found together in any sample from the Sands of Lede containing sufficient otoliths (collection IRSNB). An ontogenetic series of Muraenanguilla thevenini is figured by Nolf (2013: pl. 27, as “ Congrida ” thevenini ), and shows that larger otoliths gradually take a more elongate form and a less salient posterodorsal angle.

Stratigraphic and geographic distribution

In the American Eocene, the taxon is only known by a single specimen from the Lutetian Piney Point Formation, mentioned by Müller (1999), and by the single specimen from the Yazoo Clay, mentioned by Nolf & Stringer (2003) and refigured here ( Fig. 38H ). Some otoliths from the late Cretaceous of Mississippi may belong to the same taxon (Nolf & Stringer 1996: 441). It is also widely distributed in the Eocene of Europe, Pakistan (Nolf 1991), India and Java ( Nolf & Bajpai 1992).

Figures

Fig. 38 (opposite page). Fish otoliths from the US middle and upper Eocene. A. “Ophichthus” brevior (Koken, 1888), holotype (ZMB Ot. 26), “Jackson Beds”, Mississippi (?). B. Gnathophis dissimilis (Frizzell & Lamber, 1962), Moodys Branch F., Town Creek, Jackson, Mississippi (IRSNB P 9038). C. Paraconger solidus Müller, 1999, holotype (coll. Institut für Geowissenschaften, University of Leipzig, Nr. 10/P67), Piney Point F., loc. 24 (Horseshoe) of Müller, 1999, Virginia. D–G. Paraconger yazooensis Nolf & Stringer, 2003, Yazoo Clay, Tullos M., Copenhagen, Louisiana. D. Holotype (IRSNB P 6962). E–G. Paratypes (IRSNB P 6963–6965). H. Muraenanguilla aff. thevenini (Priem, 1906), Yazoo Clay, Copenhagen, Louisiana (IRSNB P 6966). I. Signata nicoli Dante & Frizzell, 1965, Weches F., Pleasanto, Atascosa County, Texas, holotype (USNM 23370). J. Xenosirembo decipiens (Koken, 1888), lectotype (ZMB Ot. 135), middle Eocene, “Clayborne Group”, southern USA. K. Brotula aquitanica Nolf, 1980, Yazoo Clay, Tullos M., Copenhagen, Louisiana (IRSNB P 7419). L–O. Aequalobythites aequaloides (Nolf & Stringer, 2003), Yazoo Clay, Copenhagen, Louisiana.L. Holotype (IRSNB P 6977). M–O. Paratypes (IRSNB P 6978–6980). 1 = ventral view; 2 = inner view. Scale bars = 1 mm.