Early Eocene fish otoliths from the eastern and southern USA Author Lin, Chien-Hsiang 50EBAA8C-3EE0-4655-A0BB-694D9A8F49BA Biodiversity Research Center, Academia Sinica, 128 Academia Road, Seca 2, Nankang, Taipei 11529, Taiwan. chlin.otolith@gmail.com Author Steurbaut, Etienne 9A884B23-5D05-4D6C-92B8-08B321D16845 Royal Belgian Institute of Natural Sciences, 29 Vautier Street, 1000 Brussels, Belgium. & Department of Earth and Environmental Sciences, KU Leuven, Celestijnenlaan 200 E, 3001 Leuven, Belgium. etienne.steurbaut@naturalsciences.be Author Nolf, Dirk 6BCC71A0-1BEE-4BC0-BDFC-D070609DEFAB Royal Belgian Institute of Natural Sciences, 29 Vautier Street, 1000 Brussels, Belgium. dirk.nolf@scarlet.be text European Journal of Taxonomy 2024 2024-06-04 935 203 240 https://europeanjournaloftaxonomy.eu/index.php/ejt/article/download/2557/11559 journal article 298344 10.5852/ejt.2024.935.2557 b9f405d9-04c7-4cfe-9f28-b6edc3416cb0 2118-9773 11526096 6C66A1E4-7EA4-45B7-B261-5D3ED749568E “ Conger ” biaculeatus sp. nov. urn:lsid:zoobank.org:act: 644AE8C1-D8E8-471A-B0AC-054551C98BF0 Fig. 4D–H Diagnosis OL/OH = 1.8–1.9, OsL/CaL = 0.4–0.9. Small oval otoliths with salient and pointed rostrum and posterior rim. Wide sulcus, ostium opens widely to the antero-dorsal rim, cauda straight. Large colliculum visible in cauda. Etymology The species name biaculeatus alludes to the acuminated anterior and posterior rims of the otoliths. Fig. 4. Fish otoliths from the US lower Eocene formations. A . Ariosoma sp. , Meridian, Red Hot Truck Stop, Bashi Fm., Mississippi (IRSNB P 10717). B–C . Paraconger meridies ( Frizzell & Lamber, 1962 ) , Rappahannock River, Potapaco Member, Virginia (IRSNB P 10718, P 10719). D–H . “ Conger ” biaculeatus sp. nov., Ozark, Bashi Fm., Alabama. D . Holotype (IRSNB P 10720). E–H . Paratypes (IRSNB P 10721 to P 10724). 1 = ventral view; 2 = inner view. Scale bars = 1 mm. Type material examined Holotype UNITED STATES OF AMERICA • Left otolith; Alabama , Ozark , Bashi Formation ; Fig. 4D ; IRSNB P 10720. Paratypes ( 13 in total) UNITED STATES OF AMERICA • 13 otoliths of which four are figured: Fig. 4E–H ; same collection data as for holotype; IRSNB P 10721 to P 10724 . Type locality and horizon United States of America , Ozark ( Alabama ), Bashi Formation. Fig. 5. Fish otoliths from the US lower Eocene formations. A . “ Conger ” websteri (Frost, 1933), Meridian, Red Hot Truck Stop, Bashi Fm., Mississippi (IRSNB P 10725). B . Saurida sp. , Cave Branch, Bashi Fm., Alabama (IRSNB P 10726). C . Myripristinae indet., Ridge Creek, Reklaw Fm., Texas (IRSNB P 10727). D . “ Merluccius ” papillosus ( Stinton, 1966 ), Rappahannock River, Potapaco Member, Virginia (IRSNB P 10728). E . Genartina bambergi ( Priem, 1913 ) , Meridian, Red Hot Truck Stop, Bashi Fm., Mississippi (IRSNB P 10729). F . Ariidae indet., Ridge Creek, Reklaw Fm., Texas (IRSNB P 10730). 1 = dorsal view; 2 = ventral view. Scale bars = 1 mm. Dimensions of the holotype Length = 2.69 mm ; height = 1.47 mm ; thickness = 0.69 mm . Description The newly described species “ C. ” biaculeatus sp. nov. is characterized by oval-shaped otoliths with pointed anterior and posterior rims. The otoliths are moderately thick and have smooth margins, with slightly convex inner and outer faces. The deepest part of the otoliths is in their central part, where the ventral rim is slightly angled. The sulcus is wide and not well-divided into ostium and cauda, opening antero-dorsally on the anterior rim. A large colliculum fills the sulcus, which is more visible in the cauda. The ostial crista superior curves markedly upwards, and the caudal cristae are well-developed. The cauda is short, straight, and ends well before the posterior rim, while the crista inferior is almost straight without constriction. The size of the ventral area is comparable to the dorsal one. Remarks The sulcus type of “ C. ” biaculeatus is similar to that of other species under the incertae sedis genus, such as “ C. ” prolatus and “ C. ” websteri in Lin & Nolf (2022 : figs 12d–g, 13a–c), which suggests that it may belong to an extinct taxon within the family Congridae . Stratigraphic and geographic distribution Ypresian: Bashi Formation, Alabama .