Earth and Environmental Science Transactions of the Royal Society of Edinburgh

Research Article

Silurian and earliest Devonian birkeniid anaspids from the Northern Hemisphere

H. Bloma1 p1, T. Märssa2 and C. G. Millera3

a1 Department of Earth Sciences, Historical Geology and Palaeontology, Norbyvägen 22, SE-752 36 Uppsala, Sweden.

a2 Institute of Geology at Tallinn Technical University, Estonia Avenue 7, Tallinn EE-0001, Estonia. e-mail: marss@gi.ee

a3 Department of Palaeontology, The Natural History Museum, Cromwell Road, London SW7 5BD, U.K. e-mail: G.Miller@nhm.ac.uk

ABSTRACT

The sculpture of scales and plates of articulated anaspids from the order Birkeniida is described and used to clarify the position of scale taxa previously left in open nomenclature. The dermal skeleton of a well-preserved squamation of Birkenia elegans Traquair, 1898 from the Silurian of Scotland shows a characteristic finely tuberculated sculpture over the whole body. Rhyncholepis parvula Kiær, 1911, Pterygolepis nitida (Kiær, 1911) and Pharyngolepis oblonga Kiær, 1911, from the Silurian of Norway show three other sculpture types. Northern Hemisphere disarticulated scales and plates are described here, supporting a new anaspid taxonomy that includes both articulated and disarticulated material. The diversity, distribution, evolutionary trends and biostratigraphy of anaspids are described in the context of this new taxonomy, which includes six families (two are new) subdivided into 16 genera (10 are new) and 22 species (15 are new).

New taxa among Birkeniidae Traquair, 1898 are Birkenia robusta sp. nov. and Hoburgilepis papillata gen. et sp. nov.. Rhyncholepididae Kiær, 1924 includes Rhyncholepis butriangula sp. nov., Silmalepis erinacea gen. et sp. nov., Vesikulepis funiforma gen. et sp. nov., Maurylepis lacrimans gen. et sp. nov., and the previously described Schidiosteus mustelensis Pander, 1856 and Rytidolepis quenstedtii Pander, 1856. Tahulalepididae fam. nov. is represented by Tahulalepis elongituberculata gen. et sp. nov. and the revised T. kingi (Woodward, 1947). Septentrioniidae fam. nov. contains Septentrionia lancifera gen. et sp. nov., S. mucronata gen. et sp. nov., S. dissimilis gen. et sp. nov., S. seducta gen. et sp. nov., Liivilepis curvata gen. et sp. nov., Spokoinolepis alternans gen. et sp. nov. and Manbrookia asperella gen. et sp. nov. The family level position of Ruhnulepis longicostata gen. et sp. nov. is uncertain. Pterygolepididae Obruchev, 1964 and Pharyngolepididae Kiær, 1924 remain monogeneric.

(Received July 11 2000)

(Accepted March 29 2001)

KEY WORDS

  • Agnatha;
  • Anaspida;
  • Arctic and northwestern Canada;
  • Birkeniida;
  • British Isles;
  • Central Urals;
  • correlation;
  • dermal skeleton;
  • Estonia;
  • Norway;
  • Palaeozoic;
  • Severnaya Zemlya;
  • Sweden;
  • taxonomy

Correspondence

p1 Department of Palaeontology, The Natural History Museum, Cromwell Road, London SW7 5BD, U.K. e-mail: H.Blom@nhm.ac.uk