Bibradya Strank, 1983

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 : 13

Genus Bibradya Strank, 1983

Type Species. Bibradya inflata Strank, 1983 .

Diagnosis. Janischewskinidae with irregular coiling up to the final whorl, septa bifurcated, swollen, and furrowed.

Composition. Bibradya densicamerata sp. nov.; B. grandis Strank, 1983 (=? Mirifica mirifica part); B. inflata Strank, 1983 ; B. maxima sp. nov.; B. moldensis (Strank in Somerville and Strank, 1984); B. primitiva sp. nov.; B. subita sp. nov.; B. tenella ( Ye et al., 1987) .

Remarks. The composition of this genus has been usually restricted to the original species described by Strank (1984), although Cózar et al. (2022) also included B. moldensis , the type species of the monospecific genus Groessensella , and some ancestral forms ( Bibradya ? sp. 1) from the base of the Asbian in Britain. This latter form is included herein in B. primitiva . In addition, B. tenella , originally described as a Cribrospira , is also included in the genus due to the more marked skew-coiled whorls.

Similar to the case of Cribrospira , it is possible to observe an intragenus variability of the wall structure in Bibradya , and thus, species such as B. primitiva , B. inflata , B. grandis , and B. moldensis show a more granular wall with some sparse agglutinated grains, whereas B. densicamerata , B. maxima , B. subita , and B. tenella have a typical microgranular wall. This variation seems to exist at intraspecies level, because comparing ‘ Mirifica ’ mirifica in Rauser-Chernousova (1948b, plate 5, fig. 18) and Aizenverg et al. (1968, plate 8, fig.3), both specimens are homeomorphs, belonging to the same species, but the former specimen from Russia contains some agglutinated grains, whereas the latter specimens from Ukraine shows a typical microgranular wall.

Occurrence. Late Asbian to Serpukhovian in Britain, Ireland, and China, Serpukhovian in the Sahara Platform, and in the Aleksinian from the Russian Platform ( Cózar et al., 2014a; Cózar and Somerville, 2020).

Distribution in the Bama Platform. The genus occurs from the Aleksinian ( Figure 3 ). Surprisingly, the first recorded species is B. tenella ( Figure 8G‒I ), a fact which suggests that the stratigraphic record of Bibradya primitiva is not complete in the platform, a species which only occurs in strata assigned to the Mikhailovian upwards. In the upper part of the Mikhailovian, B. densicamerata and B. maxima are first recorded. The first occurrence of B. subita coincides in the two sections at the base of the Serpukhovian, and it could be considered as a regional marker.

Figures

FIGURE 3. Distribution of the Janischewskinidae in the Kacai section. Legend and abbreviations as in Figure 2, and additionally, Alek. — Aleksinian, Tar. — Tarusian, Pr. — Protvian, up. — upper, Jdz — Janischewskina delicata Zone, Bc — Bradyina cribrostomata Zone.

FIGURE 8. Illustrations of Bibradya tenella (Ye et al., 1987) and the new species Bibradya densicamerata sp. nov. A‒F. Bibradya densicamerata sp. nov. A. HPU-KC90-406, B. HPU-KC75-488 (holotype), C. HPU-KC75-510, D. HPU- KC75-380, E. HPU-SDB155-188, F. HPU-KC75-503. G‒I. Bibradya tenella (Ye et al., 1987). G. HPU-SDB179-27, H. HPU-SDB182-7, I. HPU-SDB184-11. (Scale bar equals 1 mm).