Dictyorbitolininae Schroeder, 1990

Rashidi, Felix Schlagintweit Koorosh & Babadipour, Movlud, 2016, Orbitolinid Foraminifera From The Late Maastrichtian Of The Tarbur Formation (Zagros Zone, Sw Iran), Acta Palaeontologica Romaniae 12 (2), pp. 29-46 : 31-34

Subfamily Dictyorbitolininae Schroeder, 1990 (in Schroeder et al., 1990)

Remarks: The subfamily Dictyorbitolininae are defined as follows: “The genera assigned to this subfamily are characterized by the presence of marginal foramina, situated at the periphery of the central zone forming a circular row. These apertures are arranged along vertical lines from the apex to the base. The primary septules show the same arrangement as the apertures (Schroeder, in Schroeder et al., 1990, p. 196, translated). Schroeder attributed three genera to this subfamily: Dictyorbitolina Cherchi & Schroeder , Paracoskinolina Moullade , and Praedictyorbitolina Schroeder (see also Kaminski, 2014). Taking into account the stratigraphic ranges of these genera, the Dictyorbitolininae are so far reported from the Late Hauterivian to Albian. The youngest representative is Paracoskinolina sunnilandensis (Maync) from the Albian of the Gulf Coast Area of the United States of America ( Maync, 1955a). It should be mentioned here that Mikhalevich (2013, p. 505), referring to the above mentioned paper of Schroeder et al. (1990), distinguished two subfamilies, the Praedictyorbitolininae (including Praedictyorbitolinina, and Paracoskinolina ) and the Dictyorbitolininae (including Dictyorbitolinina). Also in the classification provided by Kaminski (2004 and 2014), one finds the Praedictyorbitolininae . Such a subdivision or subfamily names however have not been introduced by Schroeder et al. (1990) (for Dictyorbitolininae see also Schroeder et al., 1999).

Genus Dictyoconella Henson, 1948

Type-species Dictyoconella complanata Henson, 1948 Remarks: In 1948 Henson published a monography of Jurassic to Paleogene larger benthic foraminifera of south-western Asia including the description of fourteen new genera. Among these, Henson established the new genus Dictyoconella with two species, the type-species D. complanata from the Maastrichtian of Qatar, and D. minima from strata with an age of “most probably Upper Cenomanian or Turonian” of Qatar ….and “a single specimen, possibly of this species,….in Maastrichtian limestones” of Iraq (op. cit., p. 26). Both species assigned to the family Orbitolinidae were poorly illustrated. According to Henson, both possess a subepidermal polygonal pattern, and D. minima main partitions (= primary beams) that are lacking in D. complanata . The test of D. complanata is distinctly compressed with subparallel opposite sides, flabelliform (e.g., like in cuneolinids) whereas the one of D. minima only slightly may show ellipsoidal transverse sections ( Henson, 1948, pl. 11, figs. 8, 10). In addition, Henson supplied morphological details in the description of D. minima that are not discernible in the provided illustrations, e.g. the existence of a planispiral initial coil. Douglass (1960, p. 256) stated that “it is likely that the form described by Henson as Dictyoconella is merely a variant of the genus Iraqia ” …. a form where “the partitions are reticulate throughout the central area”. Although almost 80 years have passed since then, both species ascribed to the genus Dictyoconella are still very poorly known concerning both systematics and biostratigraphy.

Due to the general morphology and illustrations provided we conclude that from the two only D. minima displays the typical morphology and structure of an orbitolinid foraminifera. Therefore both species are here considered as belonging to different genera, one with a flabelliform test ( D. complanata ) and another with an orbitolinid test architecture ( D.? minima ). This interpretation excludes the belonging of D. mimima to the genus Dictyoconella .