Lactarius amplus Pomerol, 1973

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 : 207-208

Lactarius amplus Pomerol, 1973

Fig. 71 C–D

Brazosiella moseleyi Dante & Frizzell in Frizzell & Dante, 1965: 701–702 , pl. 87, figs 21, 27.

Lactarius amplus Pomerol 1973: 122 , fig. 8. — Nolf 1974: 150, pl. 1, fig. 16; 1985: 84; 2013: 101, pl. 252. — Stinton 1978: 181–182, pl. 12, figs 11–16. — Müller 1999: 152–153, pl. 32, figs 6–11.

Material examined

UNITED STATES OF AMERICA – Alabama • 34 otoliths; GLS otolith comparative collection (31 specimens), MSC 39059, WSU CC 474.3 , WSU CC 475.1 .

Description

Sagittae primarily oval in shape (sensu Smale et al. 1995); height/length ratios 82–92%. Large specimens tending to somewhat angular on dorsal margins. Small, juvenile specimens exhibit finely crenulated margins; larger and adult specimens generally have smoother margins with some lobes. Anterior margin characterized by fairly prominent, blunt rostrum with a small antirostrum and excisura. Anterodorsal slope fairly steep, varies from almost straight to slightly rounded. Dorsal margin tending to rounded, may also slope toward posterior. Posterodorsal slope tending to fairly steep. Posterior margin short, usually slightly rounded and steep. Ventral margin broadly and mainly evenly curved. Inner face convex, with prominent sulcus and fairly broad, elliptical-shaped, depressed area above sulcus. Sulcus divided (heterosulcoid type), quite long (about 90% of total otolith length), fairly well excavated. Ostium approximately 60% of cauda length, but of greater width. Ostium has elongated subquadrate shape, slants upward slightly. Anterior portion of ostium opens onto anterior margin; small antirostrum is present. Cauda narrower than ostium, margins almost parallel. Posterior of cauda very slightly flexed downward. End of cauda tapering but rounded, well separated from posterior margin. Distinct crista superior located below depressed area, extending across much of ostium and cauda. Ventral furrow generally poorly developed. Outer face irregularly and slightly concave.

Remarks

Nolf was one of the first to recognize that the fossil genus Brazosiella was actually the Recent genus Lactarius ( Nolf 1974, 1980, 1985), and Müller (1999) presented evidence that Brazosiella moseleyi should be referred to as Lactarius amplus . There has been considerable debate about Brazosiella mosleyi since its original description by Frizzell & Dante (1965). The original description of the species was based on a suite of specimens rather than the holotype, which was broken and worn, and many of the specimens in the suite were juveniles. Additionally, the holotype was not figured in the original description. Rather, the paratype was figured showing the inner and outer faces, and the image of the inner face was indistinct. Therefore, it has been difficult to evaluate the validity of the species ( Nolf 1985, 2013). A careful study of specimens of Lactarius from various middle Eocene sites does seem to indicate that there is another distinct species in addition to L. kokeni (see above). Based on Müller’s (1999) findings, we utilize the species L. amplus in this study. Interestingly L. amplus shares many features with the Recent species L. lactarius (see Nolf 1985: fig. 63d).

Müller (1999) described L. amplus from the middle Eocene Piney Point Formation of Virginia. His description was based on 117 specimens. Like L. kokeni , otoliths of L. amplus are common in many of the Claiborne formations in Alabama, Louisiana, and Texas ( Frizzell & Dante 1965; Stringer & Breard 1997; Breard & Stringer 1999; Müller 1999).

Stratigraphic and geographic range in Alabama

All the specimens of Lactarius amplus were found in the “upper” Lisbon Formation at site ACh-8. 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.