Gothograptus kozlowskii, Štorch & Manda, 2019

Štorch, Petr & Manda, Štěpán, 2019, Little Known Homerian (Lower Silurian) Graptolites From Kosov Quarry Near Beroun, The Czech Republic, Fossil Imprint 75 (1), pp. 44-58 : 47-48

Gothograptus kozlowskii KOZŁOWSKA- DAWIDZIUK, 1990

Text-figs 3 a–b, 4d–f

1990 Gothograptus (Gothograptus) kozlowskii sp. n.; Kozłowska-Dawidziuk, pp. 197–200, text-figs 3a–f, 4a–e, pl. 23, figs 1–4, pl. 24, fig. 3.

2010 Gothograptus kozlowskii KOZŁOWSKA- DAWIDZIUK; Loydell et al., fig. 4h.

2015 Gothograptus kozlowskii KOZŁOWSKA- DAWIDZIUK; Kozłowska, fig. 1A.

2019 Gothograptus kozlowskii KOZŁOWSKA- DAWIDZIUK; Manda et al., figs 7g, 10b.

H o l o t y p e. Specimen no ZPAL G.XIII/43 from a Baltic erratic boulder from Jarosławiec, Poland, figured by Kozłowska-Dawidziuk (1990: pl. 24, fig. 3).

M a t e r i a l. More than one hundred flattened, mostly complete rhabdosomes from the upper lundgreni Biozone of the Kosov 2 section (samples K2/23–K2/11; see Manda et al. 2019: fig. 2).

D i a g n o s i s. See Kozłowska-Dawidziuk (1990).

D e s c r i p t i o n. Rhabdosome comprises 9–12 pairs of thecae in mature, up to 12.6 mm long specimens with finite development. Many specimens, however, do not attain this length and full maturity. Rounded proximal end is 0.85–0.99 mm wide (M = 0.92 mm, n = 11) at the level of the first thecal apertures. The rhabdosome is parallel-sided until about the level of the fifth thecal pair, with a mean width of 0.91 mm excluding spines (n = 11), then gradually narrows in the distal part, which is terminated by a welldeveloped 0.15 mm wide and up to 1.6 mm long appendix. 2TRD increases from 1.45–1.68 mm (M = 1.55 mm, n = 11) at th2 to 1.7–1.9 mm (M = 1.77 mm, n = 10) in the middle part of the rhabdosome, and decreases to 1.3 mm in the somewhat dwarfed distal-most thecae. Reticulum is dense and prominent in mature specimens. Clathria are regular and easy to recognize in juvenile rhabdosomes, but some clathrial structures become less distinctive in mature and heavily reticulated specimens. Nema incorporated in the lateral wall continues through the whole rhabdosome, up through the appendix. Thecal apertures bear 0.21–0.3 mm long, ventrally or ventro-proximally projected clawlike lateral spines with a triangular base. The spines are thin, without a massive base in juvenile specimens.

R e m a r k s. The present material matches most parameters and characters documented in the original description of the species ( Kozłowska-Dawidziuk 1990), which was based upon chemically isolated specimens from an erratic boulder. Flattened finite rhabdosomes from the Kosov 2 section attain significantly greater maximum length (12.6 mm compared to 9.9 mm recorded in a single finite specimen from the type collection), and accordingly consist of a greater number of thecae (9–12 compared to 8 thecae reported in finite rhabdosomes of G. kozlowskii by Kozłowska et al. (2019)). The maximum width of the Kosov 2 specimens (0.99 mm) is less than the 1.24 mm recorded in the type material. Thecal spacing is denser in Kosov specimens, the well-developed reticulum and relatively thin clathrial lists correspond in the present and type specimens. Paired, claw-like curved apertural spines with broadened bases are typically developed and preserved in many rhabdosomes from the Kosov collection. The absence of the apertural spines or loops in some specimens may be a result of insufficient preservation, but a number of well-preserved finite rhabdosomes with thickened lips and obvious absence of any genicular and apertural structures in most thecae belong to a different taxon – Gothograptus aff. domeyki KOZŁOWSKA et al., 2019 . The present record of two gothograptids (species of the genus Gothograptus ) in the upper lundgreni Biozone of the Kosov section is a significant contribution to palaeobiogeographic links and intrazonal correlation of this interval between peri-Gondwanan Europe and Baltica ( Jeppsson and Calner 2003, Manda et al. 2019).

Figures

Text-fig. 3. Retiolitid graptolites from the upper lundgreni Biozone of the Kosov section. a, b – Gothograptus kozlowskii KOZŁOWSKA-DAWIDZIUK, 1990: a – PŠ 3870, finite rhabdosome with curved apertural spines from sample K2/13; b – PŠ 3878, sample K2/11. c – Semigothograptus meganassa (RICKARDS et PALMER, 2002): PŠ 3863, non-finite rhabdosome with free nema, sample K2/6. All specimens ×10, scale bar 1 mm.