Gothograptus domeyki, Kozłowska & Bates & Zalasiewicz & Radzevičius, 2019

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 : 454-457

Gothograptus domeyki n. sp.

Figs 15–16

?1952 Gothograptus nassa, Bouček & Münch , pp. 11–15, fig. 2, a–i.

Type material. Holotype number VU RET-13, mature specimen with seven pairs of thecae and appendix ( Fig. 16 A–B), Šiupyliai-69 core, 1009,1 m, lundgreni Biozone, paratype number VU RET-14, finite tubarium ( Fig. 16 C–E), Šiupyliai-69 core, depth 1010.0 m, lundgreni Biozone , Lithuania.

Etymology. Ignacy Domeyko (1802–1889) was a Polish geologist, mineralogist and educator; most of his life was spent in Chile.

Diagnosis. Gothograptus with genicular hoods of nassa type developed on the first pair of thecae; second pair of thecae may have paired spines with seams or remnants of reticulum between them; subsequent thecae lacking genicular processes except for the last theca with a reticulated hood. Distinctively thicker thecal lips than pleural and genicular lists. G othograptus domeyki differs from other Gothograptus species in the lack of genicular structures in the medial and distal thecae.

Remarks. Gothograptus domeyki n. sp. differs from other Gothograptus species in the lack of any genicular processes in most thecae as well as in having thick lips. G. domeyki n. sp. is similar to G. kozlowskii in having nassa type hoods on the first pair of thecae and reticulated hoods on the last pair of thecae. Similar reticulated hoods on the last thecae are also found in G. storchi . G. domeyki n. sp. is so far known only from Lithuania.

Bouček & Münch (1952) described some retiolitines as Gothograptus nassa , from the Czech Republic, lundgreni Biozone. Their drawings show some tubaria with thick lips, and without genicular nassa hoods, similar to those described herein for the first time in G. domeyki n. sp. Proper recognition of this form needs some detailed study.

Material. Two cores from Lithuania: Šiupyliai-69 core, depths: 1009.7 m 30 young, 12 mature; 1009.1 m 50 young, 31 mature; Vilkaviškis-131 core, depth 1095.8 m four fragments of mature specimens. Upper part of lundgreni Biozone.

Description. Mature tubaria usually have seven or eight pairs of thecae and appendix. The total length of the tubarium is about 7.0 mm, together with the appendix. The tubarium is almost parallel-sided, widest at 0.83 mm at the level of the first thecal pair, and then it slowly narrows to 0.4 mm just below the appendix.

In some mature specimens the prongs of the ancora, as well as the sicular rim and lists above the proximal lateral orifices, are extremely thick (( Fig. 16A, B, E, H, I ). An outer ancora is well developed in mature specimens. The proximal ventral orifices are overgrown by reticulum in mature colonies. Mid-ventral lists are 0.5 mm long in the first and last thecae, the rest are about 0.7 mm long.

Genicular structures start to develop when the colony reaches about five thecal pairs. There are three types of genicular structures in mature tubaria of G. domeyki n. sp. The first pair of thecae have nassa hoods; usually they are small and do not cover the orifices of thecae or they are slightly larger than the thecal orifice.

The second and third thecal pairs have a pair of curved spines grown on the pleural lists, extending horizontally. Seams on the inner sides of the spines indicate that there was a thin membrane between them, so that the spines form the sides of a hood. The bases of the spines in the mature tubaria are of triangular shape ( Fig. 16G ). Similar spines forming hoods are also found in Gothograptus kozlowskii (see below).

The next thecae have no hoods; their lips are thick, about twice as thick as the geniculum list. The genicular lists became significantly thinner in the last thecae. The last pair of thecae have reticulated hoods covering orifices; the genicular list is not developed. The reticulum of these hoods is connected with the appendix ( Fig. 16A ).

umbrella, outside view.

Some young tubaria with five pairs of thecae have reticulum up to the third pair of thecae, small nassa hoods on the first thecae, the two next pairs of thecae having thin genicular spines. A specimen with seven pairs of thecae has a well-developed reticulum, except on the two last thecae. The lists of young colonies are thin; the thickest is the nema ( Fig. 15A, D ). During astogeny the next thicker lists are the lateral apertural rods.

The lips and genicular lists are so thick that the thecal orifice is very narrow ( Fig. 15E , 16E ). The thecal orifices vary in shape from nearly rectangular to pyramidal with rounded corners ( Fig. 7A , 16C, E ). Mature colonies have a dense reticulum of similar thickness to the clathrial lists, thus the structures formed by clathrial lists are difficult to distinguish.

Figures

FIGURE 7. Thecal orifices and hoods of Gothograptus. A. Pyramidal orifices in Gothograptus domeyki n. sp., VU RET-13, Šiupyliai-69 core, Lithuania, depth 1010.0 m, upper part of lundgreni Biozone. B. rectangular orifice in Gothograptus nassa (Holm, 1890), Bartoszyce IG-1 core, depth 1656.8 m, nassa Biozone, ZPAL G.55/13.

FIGURE 15. Gothograptus domeyki n. sp. tubaria of young colonies, Šiupyliai-69 core, depth 1009.4 m, lundgreni Biozone, Lithuania. A, E, F. tubarium with five pairs of thecae, ventro-lateral view, VU RET-10; A. whole specimen; E. enlargement of orifice of th4 1; F. enlargement of orifice of th2 1. B. tubarium with six pairs of thecae, ventro-lateral view, VU RET-11. C, D. tubarium with seven pairs of thecae, VU RET-12; C. whole tubarium, lateral view; D. enlargement of orifice of th1 1.

FIGURE 16. Tubaria of mature colonies of Gothograptus domeyki n. sp., Šiupyliai-69 core, upper part of lundgreni Biozone, Lithuania. A–B. finite tubarium with seven pairs of thecae and appendix, holotype, depth 1009,1 m, VU RET-13; A. ventrolateral view of specimen; B. enlargement of thick ancora and broken outer ancora, oblique view. C, H. finite tubarium, depth 1010.0 m, VU RET-14; C. enlargement of two thecae; H. enlargement of proximal end. D–E. fragment of finite tubarium, paratype, depth 1010.0 m, VU RET-15; D. whole specimen, ventro-lateral view; E. proximal thecae with spines. F–G. proximal end of young tubarium, depth 1010.0 m, VU RET-16; F. enlargement of proximal theca; G. enlargement of ancora