The genus Planohedbergella was originally defined by Boudagher-Fadel et al. (1997) as having a macroperforate test wall, but it is not clear what size limits were used to differentiate their macroperforate from microperforate tests. Most likely their definitions followed that of Banner and Desai (1988) with microperforate having pore diameters 5 mm. It is puzzling why Boudagher-Fadel et al. (1997) considered Planohedbergella to be macroperforate when their magnified view of Planomalina ehrenbergi holotype (see Pl. 20, Figs. 6a-c for re-illustration), which is the type species of the genus, clearly shows a finely perforate test wall (Boudagher-Fadel et al. 1997, plate appendix 1, fig. 6). Moreover, the primary type (Pl. 20, Fig. 2d) and metatype (identified by original author; Pl. 20, Fig. 5c) of Globigerinelloides yaucoensis, the senior synonym of Pl. ehrenbergi, have pore diameters that range from 1.1–1.3 mm.

Species included in Planohedbergella are both microperforate and finely perforate with average pore diameters ranging from 0.8–2.0 mm, with the exception of Plh. circularis, which is exclusively finely perforate with pore diameters ranging from 1.6 to 2.0 mm and averaging 1.8 mm (Table 1). Measurement of pore diameters from additional well-preserved specimens is needed to determine whether there is phylogenetic significance to grouping of species that have average pore diameters ranging between 0.8 – 1.2 mm (i.e., Plh. aspera, Plh. multispina, Plh. prairiehillensis, Plh. yaucoensis and Plh. impensa) versus those that have average pore diameters >1.5 mm (i.e., Phl. circularis, Plh. escheri, Plh. messinae, and Plh. subcarinata).

            According to Boudagher-Fadel et al. (1997), Planohedbergella was derived from Hedbergella (=Muricohedbergella in current usage) during the Cenomanian, and their description “planospiral [sic] in adult” implies a possible trochospiral early ontogeny. The authors did not identify the ancestral species that gave rise to the genus or the direct species descendent, and they did not list which species should be included in the genus other than Phanerostomum asperum Ehrenberg, 1854, which they considered significant because it occurs in “the first publication which dealt with the form we are calling Planohedbergella”.

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