Waitakia dorsogibbosa, Lin & Steurbaut & Nolf, 2024

Lin, Chien-Hsiang, Steurbaut, Etienne & Nolf, Dirk, 2024, Early Eocene fish otoliths from the eastern and southern USA, European Journal of Taxonomy 935, pp. 203-240 : 224-225

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.

Figures

Fig. 9. Fish otoliths from the US lower Eocene formations. A–C. Preophidion arcuatus (Stinton, 1966), Cave Branch, Bashi Fm.,Alabama (IRSNB P 10750 to P 10752). D. Centroberyx sp., Hatchetigbee Bluff, Hatchetigbee Fm., Alabama (IRSNB P 10753). E. Bothidae indet., Ridge Creek, Reklaw Fm., Texas (IRSNB P 10754). F–G. Waitakia dorsogibbosa sp. nov. F. Pamunkey River, Hanovertown, Potapaco Member, Virginia, holotype (IRSNB P 10755). G. Piscataway Creek, Thrift Road ravine, Potapaco Member, Maryland, paratype (IRSNB P 10756). 1 = ventral view; 2 = inner view. Scale bars = 1 mm.

Fig. 1. Maps showing the sampling sites on the US Gulf Coastal Plain (Texas, Mississippi, and Alabama) and Atlantic Coastal Plain (A = Virginia and Maryland). 1. Ridge Creek. 2–4. Taylor’s Branch of Two Mile Creek, samples 1–3. 5. Meridian, Gallagher Creek. 6. Meridian, Red Hot Truck Stop. 7. Hatchetigbee Bluff. 8. Cave Branch. 9. Elba Dam on Pea River. 10. Ozark. 11. Pamunkey River, E of Hanover School for boys. 12. Pamunkey River, Hanovertown. 13. Pamunkey River, 1 km W of Hunters Club. 14. Pamunkey River, Hunters Club. 15. Rappahannock River. 16. Loyola Retreat House, N of Popes Creek. 17. Popes Creek, South. 18. Piscataway Creek, Thrift Road ravine.