Malacanthus ?sulcatus Cuvier 1829

Malacanthus ? sulcatus (Koken, 1888)

Fig. 71 E–F

Otolithus (Cottidarum) sulcatus Koken, 1888: pl. 18, fig. 12.

“genus Malacanthidarum ” sulcatus – Nolf 2003: 6, pl. 1, figs 14a–b. — Nolf & Stringer 2003: 4, pl. 5, figs 3a–8b.

“ Malacanthida ” sulcata – Nolf 2013: 98, pl. 238.

Material examined

UNITED STATES OF AMERICA – Alabama • 15 otoliths; GLS otolith comparative collection (14 specimens), MSC 39061.

Description

Sagittae primarily elliptical (sensu Smale et al. 1995); height/length ratios range from approximately 49– 60%. Dorsal margin with fairly coarse lobes; ventral margin fairly smooth or with much smaller lobes. Anterior margin characterized by usually bluntly tapered rostrum. Anterodorsal slope fairly steep, varies from almost straight to slightly rounded. Dorsal margin tending to rounded and lobed. Posterodorsal slope generally fairly steep; slope sometimes almost straight. Posterior margin short, usually steep, slightly rounded. Ventral margin not very deep, only slightly curved. Inner face convex, with prominent sulcus and irregularly shaped depressed area above sulcus. Sulcus divided (heterosulcoid type), quite long (about 85% of total otolith length), fairly well excavated. Ostium approximately 60% of cauda length, about same width as anterior portion of cauda. Ostium has elliptical shape. Anterior portion of ostium opens onto anterior margin. Anterior portion of cauda about the same width as ostium; width of cauda increases posteriorly. Posterior of cauda noticeably round, very slightly flexed downward. Posterior end of cauda well separated from posterior margin. Ventral furrow generally poorly developed. Outer face only slightly concave.

Remarks

Although fairly numerous at 15 specimens, the species was found at only one Claiborne Group site in Alabama (site ACh-8). The species has been reported (under the name “ Malacanthida ” sulcata) from the middle Eocene (Bartonian) Moodys Branch Formation in Mississippi (Nolf 2013). The taxon was found to be fairly common, with 57 specimens (identified as “genus Malacanthidarum ” sulcata), in the upper Eocene Yazoo Clay of Louisiana (Nolf & Stringer 2003). Like the Yazoo Clay specimens, the Claiborne Group Malacanthus ? sulcatus otoliths tended to be fairly small, with the largest being less than 4 mm in length. The otoliths of Malacanthus ? sulcatus compare very well with Recent species of Malacanthus, like M. brevirostris (see Nolf & Stringer 2003: pl. 5, figs 3–6).

Stratigraphic and geographic range in Alabama

All of the specimens were recovered from the “upper” Lisbon Formation at site ACh-8. Bartonian, zones NP16 to NP17.