Citharus

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 : 69-70

“ Citharus ” varians sp. nov.

urn:lsid:zoobank.org:act:88394BA7-3F94-45EC-A7E4-B3903364E0ED

Fig. 24

Diagnosis

OL/OH = 1.03–1.33, OsL/CaL = 0.83–1.20. Circular otoliths with small, pointed but well-developed rostrum and antirostrum. Shape of posterior rim varies markedly among specimens. Sulcus well divided into ostium and cauda.

Etymology

The name alludes to the considerable intraspecific variability of the otoliths.

Material examined

Holotype UNITED STATES OF AMERICA • Right otolith; Texas, Little Brazos River, Stenzel loc.; Wheelock Member ; Fig. 24G ; IRSNB P 10145 .

Paratypes UNITED STATES OF AMERICA • 51 otoliths of which six are figured: Fig. 24A–F ; Texas, Little Brazos River, Stenzel loc.; Wheelock Member ; IRSNB P 10139–10144 • 24 otoliths; Texas, Stone City Bluff, Brazos River ; “ Stone City Beds ” • 22 otoliths; Pin Oak Creek; Landrum Member .

Type locality and horizon

United States of America, Little Brazos River, Stenzel loc. (Texas), Wheelock Member of the Cook Mountain Formation.

Dimensions of the holotype

Length = 2.28 mm; height = 2.03 mm; thickness = 0.83 mm.

Description

This species is characterized by globally circular otoliths, but with a marked rostrum, antirostrum, and a postero-dorsal angle. The dorsal and ventral rims are smoothly curved and raised in the center. The curvature is most pronounced in the ventral rim. The dorsal rim may be irregular but it is usually smooth. The configuration of the posterior rim varies greatly. It may be vertically straight ( Fig. 24D ), or pointed and extended at the lower part, as in the holotype ( Fig. 24G ). The rostrum and the antirostrum are both small, short and pointed at their tips. The tip of the rostrum is directed upwards. The excisura is not very incised, but always well-marked with its hollow shape. The inner face is more or less flat but notably elevated in the sulcus area. The outer face varies from convex to strongly convex ( Fig. 24F 1 ). The sulcus has ridge-like cristae; it is deeply incised and with elevated collum, well divided into ostium and cauda. Both are oblong, straight, and of nearly similar length. The shape of the cauda varies in left and right otoliths; in the left ones it is somewhat shorter and more rounded; in the right ones, the posterior end is very slightly inclined ventrally.

Remarks

The otoliths of this species demonstrate the great intra-specific variation in flatfishes already mentioned by Schwarzhans (1999). The dissymmetric look of the left and right otoliths further increases this variability. Furthermore, a high variability in otolith can also be observed in many of the extant pleuronectiforms illustrated in the various papers of Chaine (see Nolf et al. 2009: pls 133–149).

Stratigraphic and geographic distribution

Lutetian: “Stone City beds”, Texas. Bartonian: Cook Mountain Formation, Texas; “upper” Lisbon Formation, Alabama.

Figures

Fig. 24. Otoliths of “Citharus” varians sp. nov. from the US middle and upper Eocene; Wheelock M., Little Brazos River, Stenzel loc., Texas. A–F. Paratypes (IRSNB P 10139–10144). G. Holotype (IRSNB P 10145). 1 = ventral view; 2 = inner view. Scale bars = 1 mm.

Fig. 1. Maps showing the sampling sites on the US Gulf and eastern Atlantic Coasts (Texas, Louisiana, Mississippi,Alabama, Virginia).A. Sites 1–23 from Texas.B. Sites 25–43 from Mississippi andAlabama. 1. Pin Oak Creek. 2. Hooker Creek. 3. Burleson Bluff. 4–10. Rocky Branch, 1.5 miles SW of Stone City Bluff, samples 0–6. 11. Stone City Bluff, Brazos River. 12. Little Brazos River, under Highway 21 bridge. 13. Little Brazos River, Stenzel loc. 14. Little Brazos River, 1.5 km S of Highway 21 bridge. 15. Little Brazos River, confluence with Brazos River. 16. Dunn’s Ranch, NNE of Bryan. 17. Robbins, roadside. 18. Wall Farm 2. 19. Wall Farm 1. 20. Cedar Creek, E of Centerville. 21. Alabama Ferry, on Trinity River, North. 22. Crockett. 23. Nacogdoces Dam. 24. Copenhagen (after Nolf & Stringer 2003). 25. Cynthia, Mississippi Lite clay pit. 26. Midway, Techeva Creek. 27. Jackson, boring at the corner of Amite and Mill Streets. 28. Jackson, Town Creek. 29. Jackson, Riverside Park. 30. Newton, NE exit off Interstate 20. 31. Dobys Bluff. 32. Quitman, Archusa Water Park. 33. Chickasawhay River, Hunting Lodge. 34. Evansboro (SE of town). 35. Puss Cuss Creek. 36. Isney. 37. Melvin (SE of town). 38. Gilbertown. 39. Barrytown, County Road 21. 40. Coffeeville Landing, samples A–D. 41. Coffeeville Landing, sample S. 42. Little Stave Creek. 43. Claiborne Bluff, Gosport F. 44. Pamunkey River, Devil’s Hole. 45. Pamunkey River, 1 km E of Eanes property. 46. Pamunkey River, Horseshoe, Old Church type locality. 47. Pamunkey River, SW of Pampatike Landing.