A redescription of Tesseraspis mosaica Karatajute-Talimaa, 1983 (Vertebrata: Pteraspidomorphi: Heterostraci) from the Lochkovian (Lower Devonian) of Severnaya Zemlya, Russia, with a review of tessellated heterostracan taxa

Alain Blieck, David K Elliott, Valentina N. Karatajute-Talimaa

Research output: Contribution to journalReview article

1 Scopus citations


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 Karatajute-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.

Original languageEnglish (US)
Pages (from-to)275-306
Number of pages32
JournalActa Geologica Polonica
Issue number3
StatePublished - Jan 1 2018



  • Comparative anatomy
  • Lochkovian
  • Severnaya Zemlya
  • Systematic review
  • Tessellated heterostracans
  • Tesseraspidiformes

ASJC Scopus subject areas

  • Geology

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