Globuligerina oxfordiana (Grigelis, 1958) – revision of the first planktonic foraminifera discovered in the Upper Jurassic of Lithuania

Abstract

The article presents the self-revision and re-description of the first planktonic foraminifera Globuligerina oxfordiana (Grigelis, 1958) discovered in the Upper Jurassic of Lithuania. The original article published in 1958 in a Russian periodical (Moscow) is translated, supplied by additional comments, and illustrated by SEM laser electronic micrographs.

Middle Jurassic (Bajocian) planktonic foraminifera from the northwest Australian margin

“…Reviews of Jurassic planktonic foraminifera are given by Grigelis and Gorbatchik (1980), Stam (1986), Simmons et al (1997), Hart et al (2002Hart et al ( , 2012, BouDagher-Fadel (2015), Gradstein 2017, and Gradstein et al (2017a, b). Other key papers are Grigelis (1958Grigelis ( , 2016, Bignot and Guyader (1971), Görög (1994), and Wernli (1995). A review of the literature on Jurassic planktonic foraminifera is beyond the scope of this paper, which focuses on the early Bajocian.…”

“…Hart et al (2012) point out that Huddleston (1982) drew attention to the fact that the type species of Globuligerina was defined as Globigerina oxfordiana Grigelis 1958, emended Bignot andGuyader 1966, which was a form with a high loop-shaped aperture and was not the original concept of Globigerina oxfordiana Grigelis 1958. Grigelis (2016) redescribed Globigerina oxfordiana, the type species of Globuligerina. His 2016 SEM photograph of the topotype (Grigelis, 2016, plate 1, fig. 3) shows the aperture as a wide, fairly low umbilical arch, in conflict with the generic definition of a high, loop-shaped aperture proposed by Simmons et al (1997), which followed the probable misidentification of Bignot and Guyader.…”

“…1, 3, 4) show higherarched apertures excentrically positioned within the umbilicus but not loop-shaped. Even a brief review of the literature (Bignot and Guyader, 1971;Grigelis and Gorbatchik, 1980;Stam, 1986;Görög, 1994;Wernli, 1995;Simmons et al, 1997;Hart et al, 2002Hart et al, , 2012BouDagher-Fadel, 2015;Grigelis, 1958Grigelis, , 2016Gradstein, 2017;Gradstein et al, 2017a, b) demonstrates the wide divergence of opinion surrounding the key features used to define Jurassic planktonic species and genera. It is noted from these literature sources that descriptions of morphological characters overlap or show transitions between species and even genera and that apertures vary considerably within species.…”

“…In her material "The presence of passage forms does not permit the establishment of separate systematic units" (Pazdrowa, 1969, p. 51), whereas in the present material, the rare narrow apertures become frequent in the population, and the form can be distinguished from G. bathoniana australiana n. ssp. G. altissapertura, with its rapidly expanding medium-high spire, is not conspecific with the low-spired G. oxfordiana (Grigelis), which was recently redescribed (Grigelis, 2016). Statements that G. oxfordiana includes forms with only three chambers in the last whorl are not supported by type specimens or by illustrations of topotype material (see Grigelis, 2016, andGradstein et al, 2017a).…”

“…G. altissapertura, with its rapidly expanding medium-high spire, is not conspecific with the low-spired G. oxfordiana (Grigelis), which was recently redescribed (Grigelis, 2016). Statements that G. oxfordiana includes forms with only three chambers in the last whorl are not supported by type specimens or by illustrations of topotype material (see Grigelis, 2016, andGradstein et al, 2017a). Due to the much higher spire of G. altissapertura and fewer chambers in the last whorl (three versus four in G. oxfordiana), as well as the very high aperture, it seems necessary to give these mediumhigh-spired Australian forms with a high-arched, "virgulineshaped" aperture a new name.…”