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 Waitakia dorsogibbosa sp. nov. urn:lsid:zoobank.org:act: 946D0B8E-FDC0-4DA4-8A24-44CBBE0F9BA0 Fig. 9F–G Diagnosis OL/OH = 1.4–1.6, OsL/CaL = 0.9–1.1. Trapezoid to triangular otoliths with strong postero-dorsal angle. Anterior and posterior rims pointed. Sulcus well-divided. Ostium wide, arrow-like with low ostial lobe tilting towards antero-ventral rim. Cauda rod-like, horizontal. Etymology ‘ Dorsogibbosus , a , um ’ = ‘hump bearing on the dorsal part’. Refers to the angulous and humpy dorsal part of the otoliths. Type material examined Holotype United States of America • Left otolith ; Virginia , Pamunkey River , Hanovertown , Potapaco Member ; Fig. 9F ; IRSNB P 10755 . Paratype UNITED STATES OF AMERICA • 1 otolith : Fig. 9G ; Maryland , Piscataway Creek , Thrift Road ravine , Potapaco Member ; IRSNB P 10756 . Type locality and horizon United States of America , Pamunkey River, Hanovertown ( Virginia ), Potapaco Member. Dimensions of the holotype Length = 2.13 mm ; height = 1.37 mm ; thickness = 0.55 mm . Description This species is characterized by small, trapezoid to triangular otoliths, with dorsal and ventral rims approximately parallel to each other and oblique anterior and posterior rims. The dorsal rim is very short, bears a strong postero-dorsal angle, and its anterior part is inclined downwards. The ventral rim is gently curved and bears an angle at each end. The thickness of the otoliths is most considerable in the middle, with both the inner and outer faces being convex ( Fig. 9F 1 ). The sulcus is well-divided into ostium and cauda, marked by a constriction of the cristae in the central zone of the sulcus. The ostium is wide, arrow-like, with a low ostial lobe expanding ventrally and tilting towards the antero-ventral rim, and its anterior tip nearly reaches the anterior rim of the otolith. The cauda is rod-like, horizontal, and shows a rounded posterior end. There is no trace of a swollen collicular crest on the caudal crista inferior like in gobiids. A dorsal depression is observed above the well-developed caudal crista superior. Remarks The otoliths of W. dorsogibbosa sp. nov. resemble most to those of Waitakia beelzebub Lin & Nolf, 2022 from the middle to late Eocene (Lutetian-Bartonian) of the southern USA and other congeners from the Eocene of New Zealand . The thick profile and sulcus morphology are characteristics for assigning the new species to the fossil genus Waitakia . However, W. dorsogibbosa has the shortest dorsal rim exhibiting a triangular outline. The species may represent one of the earliest records of this extinct lineage. It is extremely rare with only two specimens in our material. Stratigraphic and geographic distribution Ypresian: Potapaco Member, Virginia and Maryland .