Munneckella, Hussain & Rogers & Blackburn, 2022

Hussain, Rowshi, Rogers, Steven L. & Blackburn, Joel A., 2022, Ovummuridae (calcareous microfossils) from the Much Wenlock Limestone Formation, Shropshire, UK, Palaeontologia Electronica (a 27) 25 (2), pp. 1-24 : 15

Genus MUNNECKELLA gen. nov.

zoobank.org/ 61267617-5BEC-4844-BED1-4B591F2CC20F

Derivation of name. After Axel Munnecke, Friedrich-Alexander-University of Erlangen-Nürnberg, instrumental in the erection of the Ovummuridae , observed the first three-chambered variants of Ovummuridae ; genus feminine.

Type species. Munneckella tribuscamera sp. nov., the only known species.

Original diagnosis (Modified from Munnecke et al., 2000). Ovummuridae characterised by a three-chamber organisation. The morphological differences include variation in the thickness of the wall, the two pseudo-septal structures and the shape of the three chambers. The three chambers can be symmetrical and asymmetrical in size. The wall is a lamellar arrangement of calcite tablets. There are two pseudo-septums present and a cylindrical aperture can be present in either pole of the test.

Remarks. This morphotype differs from Ovummurus and Minourella in showing three (not two) chambers, divided by two pseudo-septa as originally described by Munnecke et al. (2000). The variation in chamber size between the three chambers suggests the potential for erecting further species. This could potentially be a different life cycle stage as suggested by MacNeil and Jones (2006), however, the number of observations, and the lack of any transitional evidence found, lead us to conclude that they to belong to a new species.

The genus can only be compared to a limited number of microfossils; three-chambered calcareous microfossils are rare. In cross section, foraminifera such as: Globorotalia centralis Cushman and Bermudez, 1937 , can appear three-chambered, however, Globorotalia centralis are agglutinated, and their dimensions, microstructure and number of individual chambers are completely different from those observed in Munneckella ( Tappan and Loeblich, 1988) . Ovummuridae are distinctive for the lamellar arrangement of calcite tablets in their walls and are not agglutinated.

Spores such as the Permian aged Platysaccus papilionis Potonié and Klaus, 1954 , Lueckisporites virkkiae Potonié and Klaus, 1954 and Striatopodocarpites fusus ( Balme and Hennelly, 1955) Potonié, 1958 exhibit the most similar geometry to the three-chambered organisation of Munneckella ( Balme and Hennelly, 1955 and Potonie, 1958). However, spores such as: Striatopodocarpites fusus have bisaccate morphology in which the three compartmentalisation is a product of wing-like features rather than three chambers as observed within Munneckella . The walls observed in Muneckella are also calcareous, and its structural arrangement is different to those of spores. Nannoplankton such as coccolithophores (e.g., Zygodiscaceae, Hay and Mohler, 1967 ) can have a similar three-chamber organisation as Munneckella . Isthmolithus recurves Deflandre and Fert, 1954 , is characteristic of two parallel transverse bars that form a three-compartment organisation. Although morphologically similar, these nannofossils do not share the same wall structure.

Stratigraphical range. Lower Silurian to Upper Devonian.