Netromorph acritarchs and related morphotypes in the middle Paleozoic: a proposal for classification
2025
Manzano, Eiver Gelan | Monnet, Claude | Mertens, Kenneth | Servais, Thomas
Acritarchs are organic-walled microfossils dominating the phytoplankton in Paleozoic seas. Current classification subdivides acritarchs into subgroups based on the outline of the main vesicle. Among them the netromorphs cover the fusiform morphotypes showing peak diversity during the middle Paleozoic. More than three hundred species and subspecies were reported in literature, many of which are probably synonyms or ecophenotypes. We review and emend the definition of netromorphs, restricting them to homopolar forms and reassigning related heteropolar morphotypes (Deunffia-Domasia complex) to another subgroup: the diacromorphs. We propose a simplified classification scheme as follows: i) Category 1 of elliptical forms; ii) reniform Category 2; iii) spindle-shaped Category 3 and iv) a Category 4 of crescent shaped genera. Similar-looking species within Leiofusa, Poikilofusa and Eupoikilofusa are merged into intrageneric morphotype groups. Several new combinations are proposed. The Deunffia-Domasia complex is also classified based on the presence of appendages, their number, and distal branches. Possible biological affinities of netromorphs to fungal spores, euglenids, and turbellarian (flatworm) oocytes are also discussed. However, clear biological affinities remain uncertain, and further investigation is needed to determine whether netromorphs are exclusively phytoplanktonic or belong in part to various kinds of animal, fungal or algal groups.
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