Spinograptus munchi ( Eisenack, 1951 )

Kozłowska-Dawidziuk, Anna, 2002, Agastograptus, a synonym of Plectograptus (Retiolitidae, Graptolithina), Acta Palaeontologica Polonica 47 (3), pp. 459-467 : 463-464

Spinograptus munchi ( Eisenack, 1951)

Fig. 3A, H .

Retiolites munchi n. sp.; Eisenack1951: 136, pl. 22: 9–12, pl. 23: 3–5, pl. 24: 1.

Agastograptus munchi (Eisenack) ; Obut and Zaslavskaya 1983: 111– 112, pl. 22: 4, pl. 26: 1–4.

Spinograptus munchi (Eisenack) ; Kozłowska−Dawidziuk 1995: 316– 317, figs. 31A, 32A, B.

non Agastograptus munchi (Eisenack) ; Richards, Packham, Wright and Williamson 1995: 32, figs. 18E–H, 19D–H.

Diagnosis.—See Kozłowska−Dawidziuk 1995.

Description.—The longest specimen of 10 mm, with robust lists, represents mature rhabdosome with 10 pairs of thecae. Ancora umbrella is about 1 mm wide, composed of lists thinner than in the rest of the rhabdosome. Maximum width of lateral walls (between pleural lists) is 1.6 mm at the level of 5 th pair of thecae, and is the same to end of the rhabdosome. Paired apertural processes well developed of typical shape for the species. Two first pairs of thecae possess smaller and thinner processes, the strongest are in the middle part of rhabdosome. In the distal part they are not present, probably broken off. The rest of specimens represent fragments of mature and younger (thinner lists) stages. Virgella is preserved in young rhabdosomes.

Discussion.—The new material represents the rhabdosome features as in the type material ( Eisenack 1951) as well as the material described from Všeradice, Czech Republic ( Kozłowska−Dawidziuk et al. 2001). S. munchi differs from other species of Spinograptus in lacking an ancora sleeve reticulum and mid−ventral lists (see Kozłowska−Dawidziuk 1995, 1997). It possesses distinctive, paired bifurcated reticulofusellar apertural processes, ( Fig. 3A, H ). Material described by Rickards et al. (1995) may represent some Spinograptus species, similar to S. latespinosus , with a developed reticulum. The difference between S. munchi and S. latespinosus is in the lack of reticulum of ancora sleeve and ventral walls, different shape of apertural processes as well as absence of a mid−ventral list and appendix in S. munchi .

Material.—The new material consists of dozens of fragments and 9 more complete rhabdosomes, and comes from Poland, Bartoszyce borehole depths: 1626.6 m, 1627.0 m, 1634.5 m, 1635.5 m, 1641.0 m.

Occurrence.— Spinograptus munchi probably occurs in the Colonograptus ludensis Biozone (uppermost upper Homerian) from unknown locality of erratic boulders of the Eisenack material (personal examination by the present author 1998), the Gothograptus nassa Biozone from Kaliningrad, Russia ( Obut and Zaslavskaya 1983), the lower part of the Neodiversograptus nilssoni Biozone ( Kozłowska−Dawidziuk 1995) and Colonograptus praedeubeli and C. deubeli biozones of Poland, and in the middle part of C. praedeubeli – C. deubeli Biozone of Všeradice, Barrandian, Czech Republic ( Kozłowska−Dawidziuk et al. 2001).

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.