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Middle Devonian acanthodians from Belarus - new data and interregional biostratigraphy

Plax Dmitry P., Newman Michael

Acta Geologica Polonica

2021

Vol. 71, no. 4

393--414

The Lower Devonian (Emsian) and Middle Devonian of Belarus contain assemblages of biostratigraphically useful faunal and floral microremains. Surface deposits are few, with most material being derived from borehole cores. Acanthodian scales are particularly numerous and comparison with scales from other regions of the Old Red Sandstone continent (Laurussia), specifically the Orcadian Basin of Scotland, the Baltic Region, Spitsbergen, and Severnaya Zemlya have demonstrated a lot of synonymy of acanthodian species between these areas. This is especially the case between Belarus, the Orcadian Basin and the Baltic Region, which has allowed us to produce an interregional biostratigraphic scheme, as well as to postulate marine connection routes between these areas. The acanthodian biostratigraphy of Belarus is particularly important as it is associated with spores and marine invertebrates, so giving the potential of more detailed correlations across not only the Old Red Sandstone continent, but elsewhere in the Devonian world. We also demonstrate that differences in preservation (e.g., wear and how articulated a specimen is) is one of the main reasons for synonymy.

New Late Silurian to Middle Devonian acanthodians of the Timan-Pechora region

Valiukevicius J.

Acta Geologica Polonica

2003

Vol. 53, nr 3

209-245

New Pridoli to Eifelian acanthodian scales from various structural units of the Timan-Pechora region are described. Among 15 new species and 1 new genus, there are: 10 new species of nostolepids, common members of most of the biostratigraphic associations, the monospecific genus Monospina gen. nov., a single new species of Cheiracanthoides (all Climatiida), Diplacanthus pechorensis sp. nov. (Diplacanthida), and two new species of Gomphonchus (Ischnacanthida). Besides morphologic descriptions the taxa are also characterised histologically. Acanthodian taxa with scale crowns and bases composed of cellular bone, or very similar tissue, proposed as a primitive feature in their evolution, are reported for the first time.