Gothograptus kozlowskii Kozłowska-Dawidziuk, 1990

Kozłowska, Anna, Bates, Denis, Zalasiewicz, Jan & Radzevičius, Sigitas, 2019, Evolutionary significance of the retiolitine Gothograptus (Graptolithina) with four new species from the Silurian of the East European Platform (Baltica), Poland and Lithuania, Zootaxa 4568 (3), pp. 435-469 : 457

Gothograptus kozlowskii Kozłowska-Dawidziuk, 1990

Figs 17–18

1990. Gothograptus (Gothograptus) kozlowskii, Kozłowska-Dawidziuk ; pp. 197–200; pl. 23: 1–4; pl. 24: 3; fig. 4A–E.

2010. Gothograptus kozlowskii, Loydell, Nestor & Männik ; p. 5, fig. 4h.

Material. New material of G. kozlowskii comes from Poland, Bartoszyce IG-1 core, from the upper part of the lundgreni Biozone, depths from 1677.5 to 1672.8 m, and from the testis Biozone, depth 1668.8 m. These are mostly young and fragments of mature specimens, about 30 in all. Specimens from Lithuania, Šiupyliai-69 core, occur in the upper part of the lundgreni Biozone, depths: 1010.0 m to 1008.1 m. They represent mostly fragments of about 40 mature and young tubaria.

Description. The best, completely preserved mature tubarium has fifteen thecae and a fragment of appendix. Tubarium without appendix is 6.5 mm long, 0.6 mm wide above the ancora umbrella rim. The widest part of the tubarium is at the level of the fourth thecal pair— 0.8 mm; the width then decreases slowly towards the distal thecae and at the level of seventh thecal pair it is 0.5 mm. The virgella is very thin in mature specimens. The prosicular apex is located at the level of the lip of the second theca. The nema is thicker distally. In mature specimens the connecting rods, going from nema to lips, are poorly distinguishable from other lists of the lateral wall.

The nassa type of genicular hoods of the first thecae are small, and do not cover the thecal orifices. The third pair of thecae has lateral spines with seams extending horizontally; the next thecae have hoods with a few lists of reticulum surrounded by a thick looping list. The structure extends below the lip with thicker lists bordering the structure.

From the fourth thecal pair the genicular lists are very thin, and in the last thecae are difficult to define, whereas the lips are distinctive. As with the genicular lists, the mid-ventral lists become thinner distally; they are extremely thin in the three last pairs of thecae. In flattened mature specimens, only the genicular spines on proximal thecae distinctively protrude out of the tubarium ( Fig. 17A , C–D). The most distal thecae have thick lips and very thin mid-ventral lists. The most mature specimen has extremely thick lists, the reticulum and clathrium being of similar widths, the widest about 50 µm. In these specimens the thick outer ancora umbrella covers a large part of the ancora ( Fig. 18C ).

Remarks. The new collections of Gothograptus kozlowskii from Lithuania and Poland come from the upper part of the lundgreni Biozone and from the testis Biozone. These data gave a more precise stratigraphical position of the species than the first described forms from an erratic boulder ( Kozłowska-Dawidziuk 1990). Colonies of this species also occur in Latvia in the upper part of the lundgreni Biozone ( Loydell et al. 2010). Radzevičius (2006, fig. 4G, H, I) illustrated juvenile Gothograptus specimens from the lundgreni Biozone of the Šiupyliai-69 borehole ( Lithuania) and identified them as Gothograptus cf. kozlowskii . There are not enough features to identify them to the proper species.

Figures

FIGURE 17. Mature tubaria of Gothograptus kozlowskii Kozłowska-Dawidziuk, 1990 from the Šiupyliai-69 core, depth 1009.1 m, lundgreni Biozone, Lithuania. A–E. mature tubarium with seven pairs of thecae, VU RET-17; A. whole specimen, ventro-lateral view; B. enlargement of distal part of tubarium; C. enlargement of medial part of tubarium; D, E. orifice of th3 1. F. fragment of mature tubarium showing overgrown proximal ventral orifice, ventral view, VU RET-18.

FIGURE 18. Details of mature tubarium of Gothograptus kozlowskii Kozłowska-Dawidziuk, 1990 holotype, ZPAL G.XIII/43, Baltic erratic boulder 147 from Jarosławiec, Poland. A. ventral view; B. lateral view, reverse side of tubarium; C. proximal end, outside view; D. orifice of th5 1; E. opening of appendix.