Lingulina seminuda Hantken, 1875

Bergh, Eugene W. & Compton, John S., 2022, Taxonomy of Middle Miocene foraminifera from the northern Namibian continental shelf, Zootaxa 5091 (1), pp. 1-55 : 12

Lingulina seminuda Hantken, 1875

Pl. 1, fig. 20

Lingulina costata var. seminuda Hantken, 1875, p. 41 –42, pl. 4, fig. 8a–b.

Lingulina seminuda Cushman & Jarvis, 1930, p. 361 , pl. 33, fig. 3a–b; LeRoy & Levinson, 1974, p. 8, pl. 4, fig. 10–11; Cicha et al, 1998, p. 111, pl. 22, fig. 2; Horváth, 2003, p. 13, pl. I, fig, 13, pl. II, fig, 13.

Description: The test wall is calcareous, smooth and finely perforate. The test is large, biconvex, ovate in outline, uniserial and rectilinear. The length of the test is slightly greater than the width. Three distinct chambers can be seen rapidly increasing toward the apertural end. The final chamber is inflated and much larger than the initial two chambers, comprising approximately three quarters of the test size. Costae stretch along the margin of the test, from the apical end towards the apertural end. The aperture is an elongate terminal slit.

Remarks: This Lingulina species differs from Lingulina costata in that it is more globular in shape, does not have costae throughout the test surface, but only at the margins. The initial chambers are smaller than those in Lingulina costata . The Lingulina seminuda specimens from this study best resemble Lingulina sp. B in Robertson (1998, p.54, pl.18, fig. 1) and are slightly more inflated than the specimen described in LeRoy & Levinson (1974). The sutures are slightly less depressed than L. seminuda in Cushman & Jarvis (1930) and Jones (1994).

Only a few specimens (<1% of the total foraminifera assemblage in core 2670) of Lingulina seminuda were identified in this study. The test size of specimens in this study ranges between ~1 and 2 mm in diameter. Cushman & Jarvis (1930) mention Lingulina seminuda tests from Jamaica to be up to 2.5 mm. LeRoy & Levinson (1974) had test sizes of up to 2.1 mm in length and 1.4 mm in breadth, while Horváth (2003) had a size range of 1.5 to 2 mm in length and 1.2 to 1.6 mm in width.

Life strategy: Species of the genus Lingulina are shallow infaunal and inhabit low energy, deep environments in soft muddy substrates ( Reolid et al., 2013).

Global stratigraphic range: Jones (1994) identified the stratigraphic range of L. seminuda to be Pleistocene to Recent, but specimens of L. seminuda have also been documented to occur in Miocene-aged deposits ( Cushman & Jarvis, 1930; Cicha et al., 1998).

Regional occurrence: This species occurs in middle Miocene sediments of the Namibian outer continental shelf, south of the Kunene River mouth (this study).