TY - JOUR N2 - Material of tesseraspids (Tesseraspidiformes) is reported from the uppermost Severnaya Zemlya Formation (Lochkovian, Lower Devonian) of the Severnaya Zemlya archipelago, in the Russian Arctic, where it is associated with other vertebrate remains, including corvaspids, acanthodians, and large but rare specimens of osteostracans. The tesseraspid material is not abundant, and most often preserved as a “patchwork” of bony platelets (tesserae), except for a few partly articulated specimens. We redescribe the holotype of Tesseraspis mosaica Karatajūtė-Talimaa, 1983, whose head carapace is preserved as a flattened tube of adjacent tesserae. This material is compared to the already published tesseraspid taxa, i.e., T. tessellata Wills, 1935, T. toombsi Tarlo, 1964, T. mutabilis (Brotzen, 1934), T. oervigi Tarlo, 1964 emend. Dineley and Loeffler, 1976, T. denisoni Tarlo, 1964, and T. talimaae Tarlo, 1965. All species are based upon rare and incomplete material, as no head carapaces associated with trunk and tail are known, and so, the intraspecific variability is also unknown. Distinction between “species” is based on the detail of the superficial sculpture of the tesserae of the head carapaces, which is unsatisfactory. It is concluded that only four of the nominal species can be retained. A review of all other known tessellated pteraspidomorphs indicates that our knowledge of tessellated heterostracans is currently insufficient to support a meaningful classification. L1 - http://journals.pan.pl/Content/108903/PDF-MASTER/02_Blieck.pdf L2 - http://journals.pan.pl/Content/108903 PY - 2018 IS - No 3 EP - 275–306 KW - Tessellated heterostracans KW - Tesseraspidiformes KW - Lochkovian KW - Severnaya Zemlya KW - Comparative anatomy KW - Systematic review A1 - Blieck Alain A1 - Elliott, David K. A1 - Karatajūtė-Talimaa, Valentina N. PB - Komitet Nauk Geologicznych PAN PB - Wydział Geologii UW VL - vol. 68 DA - 2018.10.01 T1 - A redescription of Tesseraspis mosaica Karatajūtė-Talimaa, 1983 (Vertebrata: †Pteraspidomorphi: Heterostraci) from the Lochkovian (Lower Devonian) of Severnaya Zemlya, Russia, with a review of tessellated heterostracan taxa. SP - 275–306 UR - http://journals.pan.pl/dlibra/publication/edition/108903 T2 - Acta Geologica Polonica ER -