Neogothograptus balticus ( Eisenack, 1951 )

Kozłowska-Dawidziuk, Anna, 2002, Agastograptus, a synonym of Plectograptus (Retiolitidae, Graptolithina), Acta Palaeontologica Polonica 47 (3), pp. 459-467 : 465

Neogothograptus balticus ( Eisenack, 1951)

Fig. 3B, E, F .

Retiolites balticus Eisenack ; Eisenack 1951: 134–136, pl. 22: 4–8, pl. 24: 5.

Gothograptus nassa (Holm) ; Moberg and Törnquist 1909: 19, pl. 1: 14.

Holoretiolites (Balticograptus) balticus Eisenack ; Bouček and Münch 1952: 17–19, fig. 5b.

Neogothograptus balticus (Eisenack) ; Kozłowska−Dawidziuk 1995: 304, fig. 27I.

Diagnosis.—See Kozłowska−Dawidziuk 1995.

Description.—The preservation and features (measurements of thecae, ancora umbrella, ancora sleeve, apertural processes) of the new material are consistent with N. balticus described before ( Eisenack 1951; Kozłowska−Dawidziuk 1995).

Discussion.— Neogothograptus balticus demonstrates the presence of a strong, clearly single, reticular apertural hood ( Fig. 3E, F ), in contrast to the paired processes of Spinograptus ( Fig. 3C, G ).

The specimen described as G. nassa by Moberg and Törnquist (1909) was examined by the author in 1993 in Lund University, and was recognized to be N. balticus . It possesses less ancora sleeve reticulum than G. nassa , distinctive single reticular apertural processes, and an ancora sleeve list arrangement characteristic of N. balticus , as well as a free nema. These features contrast to the dense ancora sleeve reticulum, solid microfusellar apertural hood, and nema incorporated to the ancora sleeve wall of G. nassa (see Kozłowska−Dawidziuk 1999), a species restricted to the P. dubius – G. nassa Biozone. The Moberg and Törnquist specimen co−occurs with the same Ludlow assemblage of graptolites Neodiversograptus nilssoni , Plectograptus macilentus , and Spinograptus spinosus , like the type.

Material.— 16 specimens from Baltic erratic boulder 46 from Jarosławiec, Poland, containing of N. balticus and Plectograptus macilentus , Saetograptus chimaera , Bohemograptus bohemicus , Neodiversograptus beklemishevi , Pristiograptus dubius , Monoclimacis sp. , and Crinitograptus crinitus ?.

Occurrence.— Neogothograptus balticus occurs in Neodiversograptus nilssoni Biozone from erratic boulder of Kaliningrad area, Russia ( Eisenack 1951), in Lobograptus progenitor ( Kozłowska−Dawidziuk 1995) and in Bohemograptus bohemicus biozones of Poland (see above).

Figures

Fig. 3. A, H. Spinograptus munchi (Eisenack, 1951), A. ZPAL G. 27/3, EEP, Bartoszyce borehole, depth 1626.6 m, reverse view of mature rhabdosome. H. ZPAL G. 27/7, EEP Mielnik borehole, depth 1044.0 m, enlargement of paired apertural processes of distal theca. B, E, F. Neogothograptus balticus (Eisenack, 1951), Baltic erratic boulder 46 from Jarosławiec. B, E. ZPAL G. 27/4 mature rhabdosome with appendix (photo D. Bates). B. Reverse view. E. Ventral view of thecae 12 side. F. ZPAL G. 27/5 enlargement of single reticular apertural process. C, G. Spinograptus clathrospinosus (Eisenack, 1951), C. GSC120736, Arctic Canada, Cornwallis Island, AB−97 25 m, stereopair of immature rhabdosome, reverse view (modified after Lenz and Kozłowska− Dawidziuk 2002: fig. 13: 6). G. ZPAL G. 27/6, EEP, Bartoszyce borehole, depth 1631.2 m, paired apertural processes of medial theca. D. Cometograptus nevadensis (Berry and Murphy, 1975), GSC 99161, Arctic Canada, Cornwallis Island, SBC10E (modified after Lenz 1993: pl. 19: 1), ventro−latral view of rhabdosome. Scale bars 1 mm except for D, F–H which is 0.5 mm. Abbreviations as Fig. 2.