Parajanischewskina nautiliformis, Liu & Vachard & Cózar & Coronado, 2023

Liu, Chao, Vachard, Daniel, Cózar, Pedro & Coronado, Ismael, 2023, New species and evolution of the foraminiferal family Janischewskinidae in the middle-upper Mississippian of South China, Palaeontologia Electronica (a 2) 26 (1), pp. 1-27 : 19-21

Parajanischewskina nautiliformis sp. nov.

Figure 11E‒I

zoobank.org/ A5097972-22E2-4A92-AA53-5A69AC993459

2006 Parajanischewskina ? sp. 1.― Cózar and Somerville, pl. 1, fig. 2.

Derivation of the Name. For the nautiloid form of the test.

Material. Holotype ( HPU-KC75-391 , Figure 11F ) and six paratypes ( Table 7 ).

Repository. School of Resources and Environment, Henan polytechnic University .

Type Locality and Horizon. Kacai section, Tarusian (early Serpukhovian).

Occurrence. Early Serpukhovian.

Diagnosis. Parajanischewskina with keriothecal wall presenting in the 4 final septa and chambers.

Description. Large nautiloid test with umbilical areas poorly depressed (e.g., Figure 11E ), ranging from 1150 μm in diameter for specimens of 2 whorls up to 2150 μm for 3‒3.5 whorls. Width of the test in the umbilical region in well-oriented specimens 1200 μm. Coiling is planispiral throughout, only the first whorl slightly endothyroid. Progressive evolution rate, composed of a low number of chambers per whorl, 6‒6.5 in the final whorl. Septa are thin in the inner whorls, curved backward, passing to thick septa with keriotheca in the final 4‒5 chambers, up to 110 μm thick. Normally microgranular wall in the rest of the test, comparatively thin, 30‒50 μm thick. Cribrate apertures in the last 3‒4 chambers.

Remarks. Differs from P. brigantiensis for the occurrence of the keriotheca in more numerous septa and parts of the wall, as well as lower number of chambers per whorl.

Figures

FIGURE 11. Typical representatives of the genus Parajanischewskina. A‒B. Parajanischewskina brigantiensis Cózar and Somerville, 2006, A. 3889-181, B. 3889-182, Limestone A8, top Iogla Formation, right bank of the Msta River, Western Moscow Basin (see Savitsky et al., 2015 for stratigraphical details). C‒D. Parajanischewskina brigantiensis, C. HPU-KC75-5, D. HPU-SDB143-16. E‒I. Parajanischewskina nautiliformis sp. nov., E. HPU-KC87-26, F. HPU- KC75-391 (holotype) G. HPU-KC87-487, H. HPU-KCT4-4, I. HPU-KC75-484. (Scale bar equals 1 mm).