Lactarius kokeni Frizzell & Dante, 1965

Ebersole, Jun A., Cicimurri, David J. & Stringer, Gary L., 2019, Taxonomy and biostratigraphy of the elasmobranchs and bony fishes (Chondrichthyes and Osteichthyes) of the lower-to-middle Eocene (Ypresian to Bartonian) Claiborne Group in Alabama, USA, including an analysis of otoliths, European Journal of Taxonomy 585, pp. 1-274 : 205-207

Lactarius kokeni Frizzell & Dante, 1965

Fig. 71 A–B

Brazosiella kokeni Dante & Frizzell in Frizzell & Dante, 1965: 700–701 , pl. 87, figs 25, 30, 32–34, 36.

Lactarius kokeni – Nolf 1985: 84 ; 2013: 101, pl. 252. — Breard & Stringer 1999: 135. — Müller 1999: 151–152, pl. 32, figs 12–16.

Material examined

UNITED STATES OF AMERICA – Alabama • 48 otoliths; GLS otolith comparative collection (47 specimens), MSC 39058 .

Description

Shape of sagittae primarily elliptical (sensu Smale et al. 1995); height/length ratios moderately high at 68–76%. Small, juvenile specimens with finely scalloped margins; larger and adult specimens with smooth margins. Prominent, blunt rostrum with small antirostrum and excisura characterize anterior margin. Anterodorsal slope straight, fairly short. Dorsal margin nearly straight, longer than anterodorsal and posterodorsal slopes. Posterodorsal slope straight and gentle. Posterior broadly rounded on small specimens, narrowly rounded for larger specimens. Ventral margin broadly and unevenly curved. Inner face slightly convex, with prominent sulcus and depressed area above sulcus. Sulcus divided (heterosulcoid type), quite long (about 90% of total otolith length), well excavated. Ostium almost equal in length to cauda, but with markedly greater width. Ostium has elongated subquadrate shape, slants upward slightly.Anterior portion of ostium opens onto anterior margin, small antirostrum present. Cauda, narrower than ostium, has subparallel margins. Posterior of cauda very slightly flexed downward. End of cauda rounded, well separated from posterior margin. Distinct crista superior occurs below strongly depressed area, which is located above most of ostium and cauda. Ventral furrow absent or poorly developed. Outer face irregularly and slightly convex, becoming concave near anterior margin.

Remarks

Lactarius kokeni is common in many of the formations of Claibornian age occurring in Texas and Louisiana ( Frizzell & Dante 1965; Stringer & Breard 1997; Breard & Stringer 1999). The species has been previously reported from the Lisbon Formation in Monroe and Choctaw counties in Alabama ( Frizzell & Dante 1965). Our analysis showed that L. kokeni is one of the most common species in the Claiborne Group of Alabama, with 48 identified specimens available to us for study.

Stratigraphic and geographic range in Alabama

Lactarius kokeni specimens were found in the “upper” Lisbon Formation at site ACh-8 and the Gosport Sand at site ACl-4. Bartonian, zones NP16 and NP17.

Figures

Fig. 71. Claiborne Group, “upper” Lisbon Formation, otoliths. A–B. Lactarius kokeni Frizzell & Dante, 1965, MSC 39058. A. Inner face (right sagitta). B. Dorsal view. —C–D. Lactarius amplus Pomerol, 1973, MSC 39059. C. Inner face (left sagitta). D. Dorsal view. — E–F. Malacanthus? sulcatus (Koken, 1888), MSC 39061. E. Inner face (left sagitta, cauda worn). F. Dorsal view. — G–H. Orthopristis burlesonis Frizzell & Dante, 1965, MSC 39060. G. Inner face (left sagitta). H. Dorsal view. — I–J. Haemulon? obliquus (Müller, 1999), MSC 39062. I. Inner face (left sagitta). J. Dorsal view. — K–L. Anisotremus? sp., MSC 42236. K. Inner face (right sagitta). L. Dorsal view. — M–N. Percoidei, indet. 1, MSC 39063. M. Inner face (right sagitta). N. Dorsal view. — O–P. Sciaena intermedius (Koken, 1888), MSC 39050. O. Inner face (left sagitta). P. Dorsal view. — Q–R. Jeftichia copelandi Frizzell & Dante, 1965, MSC 39053. Q. Inner face (right sagitta, worn, especially anterior margin). R. Dorsal view. Scale bars: A–J, O–P=2 mm; K–L, Q–R =5 mm; M–N= 1 mm.