Giganteograptus giganteus ( Bouček and Münch, 1944 )

Lenz And Anna Kozłowska, Alfred C., 2007, New and unusual upper Llandovery graptolites from Arctic Canada, Acta Palaeontologica Polonica 52 (3), pp. 489-502 : 497-499

Giganteograptus giganteus ( Bouček and Münch, 1944)

Figs. 2D, F, 6A, B, 7.

1944 Plegmatograptus giganteus sp. nov.; Bouček and Münch 1944: 16, figs. 5b, c; 6a–c.

1982 Pseudoplegmatograptus giganteus ( Bouček and Münch, 1944) ; Lenz 1982: 41, figs. 17c, d.

1994 Pseudoplegmatograptus giganteus ( Bouček and Münch, 1944) ; Štorch 1994: 180, pl. 2: 2.

2003? Pseudoplegmatograptus? giganteus ( Bouček and Münch, 1944) ; Loydell et al. 2003: fig. 7n.

Studied material.—Three incomplete, isolated specimens without proximal ends, two illustrated in Fig. 6. Two mature, flattened specimens, from the Northwest Territories, Canada and the Czech Republic are illustrated for comparison ( Fig. 2D, F).

Description.—Rhabdosome incomplete, lacking proximal end; about 5 mm wide exclusive of thecal spines. Skeletal framework of thin lists forming very coarse, orderly, polygonal meshwork, more or less arranged in at least three crude mesh rows. Thecal rims well marked, margins possessing transverse rods and connecting rods, as well as of the late Wenlock Cometograptus Kozłowska−Dawidziuk, 2001 (see Kozłowska−Dawidziuk 2001; Lenz and Kozłowska−Dawidziuk 2001) with the transverse rods, but no connecting rods.

The occurrence of pustules on G. giganteus at this period of time may be significant, since three other unrelated pustule−bearing genera, Paraplectograptus , Pseudoplectograptus , and Sokolovograptus , also first appear in the Telychian ( Kozłowska−Dawidziuk and Lenz 2001).

The species has been reported from Telychian strata of Latvia ( Loydell et al. 2003), but that specimen is considered too fragmentary for confident identification.

Stratigraphic and geographic range.—As for the genus.