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 Symmetrosulcus virginicus sp. nov. urn:lsid:zoobank.org:act: 72E254E4-1823-4F6B-9E38-3C7F45389634 Fig. 7C–F Diagnosis OL/OH = 1.7–1.8, OsL/CaL = 1.0–1.4. Elliptic otoliths with angled posterior rim. Concave postero-ventral rim. Dorsal and ventral rims gently curved. Anterior rim blunt. Sulcus very wide and elongate. Ostium slightly longer than cauda, similar width, each filled with colliculum. Fig. 7. Fish otoliths from the US lower Eocene formations. A . Glyptophidium polli (Casier, 1946) , Pamunkey River, Hanovertown, Potapaco Member, Virginia (IRSNB P 10738). B . “ Neobythites ” constrictus Stinton, 1977 , Rappahannock River, Potapaco Member, Virginia (IRSNB P 10739). C–F . Symmetrosulcus virginicus sp. nov. , Pamunkey River, Hanovertown, Potapaco Member, Virginia. C . Holotype (IRSNB P 10740). D–F . Paratypes (IRSNB P 10741 to P 10743). G . “ Neobythites ” pamunkeyensis sp. nov., Pamunkey River, Hanovertown, Potapaco Member, Virginia, holotype (IRSNB P 10744). 1 = ventral view; 2 = inner view. Scale bars = 1 mm. Etymology ‘ Virginicus , a , um ’ = ‘from Virginia’. The name alludes to the state, where the holotype was collected. Type material examined Holotype UNITED STATES OF AMERICA • Left otolith ; Virginia , Pamunkey River , Hanovertown , Potapaco Member ; Fig. 7C ; IRSNB P 10740 . Paratypes ( 51 in total) United States of America • 44 otoliths of which three are figured: Fig. 7D–F ; same collection data as for holotype; IRSNB P 10741 to P 10743 • 3 otoliths ; Alabama , Hatchetigbee Bluff, Hatchetigbee Formation ; IRSNB • 1 otolith ; Maryland , Loyola Retreat House , N of Popes Creek , Woodstock Member; IRSNB • 3 otoliths ; Maryland , Piscataway Creek , Thrift Road ravine, Potapaco Member; IRSNB . Type locality and horizon United States of America , Pamunkey River, Hanovertown ( Virginia ), Potapaco Member. Dimensions of the holotype Length = 3.41 mm ; height = 1.96 mm ; thickness = 1.38 mm . Description The otoliths of this new species are elliptical in shape, with a blunt anterior rim and a well-marked posterior angle. The dorsal and ventral rims are gently curved, and their deepest part is in the middle of the otoliths, giving them a regular, rounded appearance.All margins are smooth, and the otoliths are considerably thick, with both the inner and outer faces being convex ( Fig. 7C 1 ). A straight, wide, and well-divided sulcus occupies nearly the entire length of the inner face and is located in the central zone of the otoliths. The ostial and caudal parts are each fully filled by a colliculum. The ostium reaches the anterior margin, while the cauda extends backward to the origin of the posterior angle but does not reach the posterior margin. The cauda is slightly shorter than the ostium. The ventral area is of similar size as the dorsal one. Remarks The general shape of the otoltihs and the caudal type of this new species are similar to those of Symmetrosulcus meyeri ( Koken, 1888 ) (see Lin & Nolf 2022 : fig. 18a–f), whereas the thickness of the otoliths is similar to that of the otoliths of Preophidion , such as P. elevatus ( Koken, 1888 ) and P. granus ( Müller, 1999 ) . However, the otoliths of the new species exhibit a concavity on the postero-ventral rim, and its sulcus is much wider than that of S. meyeri . On the other hand, the cauda of the new species does not bend as strongly as that of Preophidion . The sulcus of the new species suggests that it is more similar to Symmetrosulcus than to Preophidion . Stratigraphic and geographic distribution Ypresian: Hatchetigbee Formation, Alabama ; Potapaco Member, Virginia and Maryland ; Woodstock Member, Maryland .