Pristiograptus dubius paezerensis, Urbanek & Radzevičius & Kozłowska & Teller, 2012

Urbanek, Adam, Radzevičius, Sigitas, Kozłowska, Anna & Teller, Lech, 2012, Phyletic evolution and iterative speciation in the persistent Pristiograptus dubius lineage, Acta Palaeontologica Polonica 57 (3), pp. 589-611 : 604

Pristiograptus dubius paezerensis subsp. nov.

Figs. 5F, G, 6C, D, E, 8F–I, 9A, B .

2003 Pristiograptus dubius var. B; Radzevičius 2003: 7–8, figs. 8, 9. 2006 Pristiograptus dubius var. B; Radzevičius 2006: 337, fig. 4B.

Etymology: After Paežeriai village and borehole in Lithuania.

Holotype: VU−222−229, isolated rhabdosome with with sicula and five thecae illustrated in Radzevičius 2003: fig. 8A.

Type locality: Paežeriai−222 borehole, depth 730 m, Lithuania.

Type horizon: Upper Wenlock, C. lundgreni Biozone.

Material.— About 20 rhabdosomes and many fragments from boreholes: Paežeriai−222 (734.5– 730 m), Likënai−369 (577– 605.9 m), Šiupyliai−69 (1007 m) boreholes, Lithuania and Zawada−1 (1546.5–1552.7 m), Bartoszyce IG−1 (1665.3– 1663.2 m) boreholes, Poland .

Diagnosis.—Thecal lip distinct, extending onto the ventral wall of the succeeding theca up to the middle of the ventral wall, not reaching its apertural lip. First theca starts 0.3 mm above the sicular aperture. Long virgella. No sicular rings.

Description.—The rhabdosome is straight and narrow, L is> 12.5 mm, W is 0.7 mm at th 1, 0.75 mm at th 2, 0.85 mm at th 3, 0.95 mm at th 4, and 1mm at th 5. Wmax is 1.1 mm on th 6. The interapertural W is 0.5 mm at th 1, 0.6 mm at th 2, 0.75 mm at th 3, 0.8 mm at th 4, and 0.9 mm at th 5. There are 10–11 thecae in 10 mm. Thecae are cylindrical. The angle ss is obtuse. The free part of each theca is half of its entire length. The thecal lip is distinct, the end of thecal lip may continue up to the half length of the free part of succeeding thecae. The λ angle is 30°. The sicula L is 2 mm, apertural W is 0.35 mm. The apex of the sicula is at approximately at the level of the apertural lip of th 2. Th 1 arises 0.3 mm above the sicular aperture. The virgella is thin, L to 1.35 mm.

Remarks.—The thecal apertural lips are thick and distinctive and interthecal septa of astogenetically old rhabdosomes are very thick ( Fig. 10A, B ).

Stratigraphic and geographic range.—Upper Wenlock, C. lundgreni Biozone ; Poland and Lithuania.

Figures

Fig. 9. SEM micrographs of the graptolite Pristiograptus lodenicensis Přibyl, 1943; Cyrtograptus lundgreni Biozone, Lower Homerian, Wenlock. A–D, F. Zawada borehole, Poland. A–C. Depth 1546.5–1552.7 m. A. ZPAL G. 44/13, general view of rhabdosome (A), lips of th3 and th4 (A), and th1 1 2 with sicula (A3). B. ZPAL G.44/14, general view of dorsal side of rhabdosome (B1), proximal end (B2). C. ZPAL G.44/15, general view of rhabdosome. D, F. Depth 1540–1546.5 m. D. ZPAL G.44/16, proximal end of rhabdosome. F. ZPAL G.44/17, proximal end of rhabdosome (F) and th2 lip with cortical 1 tissue “script” (“manta ray wing”) (F2). E. VU P.P9−4b, Parovėja−9 borehole, Lithuania, depth 561.9 m, general view of rhabdosome (E1), depressions of thecal apertural lip (E2).

Fig. 10. SEM micrographs of two Homerian (Wenlock) graptolite Pristiograptus forms. A, B. Pristiograptus dubius paezerensis subsp. nov., mature rhabdosomes; Cyrtograptus lundgreni Biozone. A. ZPAL G.44/17, Bartoszyce IG−1 borehole, Poland, depth 1663.2 m. B. ZPAL G.44/19, Zawada borehole, Poland, depth 1555.9–1562 m. C, D. Pristiograptus dubius parvus Ulst, 1974 growing rhabdosomes, Bartoszyce IG−1 borehole, Poland, depth 1660.7 m; Pristiograptus parvus Biozone. C. ZPAL G.44/25. D. ZPAL G.44/26.