Giganteograptus, Lenz & Kozlowska, 2007

Lenz And Anna Kozłowska, Alfred C., 2007, New and unusual upper Llandovery graptolites from Arctic Canada, Acta Palaeontologica Polonica 52 (3), pp. 489-502 : 497

Genus Giganteograptus nov.

Derivation of the name: Referring to the large size of the rhabdosome.

Type and only species: Giganteograptus giganteus ( Bouček and Münch, 1944) .

Species included: Giganteograptus giganteus ( Bouček and Münch, 1944) . It is possible that “ Pseudoplegmatograptus ” obscurus Bouček and Münch, 1944, also with a very delicate and coarse skeletal framework, might be assignable to the new genus, although without knowledge of its micro−ornamentation, this cannot be confirmed.

Diagnosis.—Rhabdosome large, with coarse, orderly polygonal meshwork without reticulum. Thecal lists composed of transverse rods, connecting rods present in proximal and medial parts of rhabdosome, lateral apertural rods, and lips with paired apertural spines projecting proximolaterally. Transverse rods close to thin nema similar to Paraplectograptus Bouček and Münch, 1948 . Nema free in distal part of rhabdosome. Ancora sleeve reduced only to pleural lists, slanted lateral lists. Micro−ornamentation of outward facing pustules.

Discussion.—The lack of any part of the proximal end ancora umbrella in the studied material, as well as in the illustrated Czech material, makes comparisons somewhat difficult. Nevertheless, the rhabdosomal framework is fairly clear ( Fig. 2D).

The list surfaces with micro−ornamentation on bandages observed in this species firmly places it in the subfamily Plectograptinae (e.g., Lenz and Melchin 1987; Lenz 1993; Kozłowska−Dawidziuk 2001; Bates et al. 2005).

Stratigraphic and geographic range.— Monoclimacis griestoniensis – crenulata Biozone , upper Telychian, Llandovery, Czech Republic; Cyrtograptus sakmaricus Biozone , uppermost Telychian, Llandovery, Arctic Canada; and Oktavites spiralis Biozone of Delorme Range, Mackenzie Mountains, Northwest Territories, Canada.