Pristiograptus dubius magnus, 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 : 603-604

Pristiograptus dubius magnus subsp. nov.

Figs. 5C, 7E, F.

2003 Pristiograptus dubius var. “A”; Radzevičius 2003: 6–7, figs. 5–7. 2008 Pristiograptus dubius var. A Radzevičius, 2003; Radzevičius et al. 2008: 38, fig. 4C.

2010 Pristiograptus dubius var. A sensu Radzevičius, 2003: Loydell et al. 2010: 256, fig. 3s, t.

Etymology: From Latin magnus, great, grand.

Holotype: VU−9−220, isolated rhabdosome with with sicula and 11 thecae illustrated in Radzevičius 2003: fig. 5A.

Type locality: Parovėja−9 borehole, depth 605.25 m, Lithuania.

Type horizon: Lower Wenlock, C. perneri Biozone.

Material.—About 25 rhabdosomes and additional fragments from the Parovėja−9 borehole (605.25– 590.5 m), Lithuania, depth and Zawada−1 borehole (1577.5–1582.5 m), Poland.

Diagnosis.—Thecal lips distinct and connected with those of succeeding thecae. No sicular rings.

Description.—The rhabdosome is robust and straight, although some specimens show ventral curvature proximally. L is> 11.5 mm. The rhabdosome widens gradually from 0.8 mm at th 1, to 0.9 mm at th 2, 1 mm at th 3, and 1.2 mm at th 4. Wmax is 1.7 mm. The interapertural W is 0.55 mm at th 1, 0.65 mm at th 2, 0.85 mm at th 3, 0.95 mm at th 4, and 1.05 mm at th 5. There are 10–11 thecae in 10 mm. The ss angle is obtuse. Th 1 is 1 mm long. The free part of each theca is half of

http://dx.doi.org/10.4202/app.2010.0070

its whole length. The thecal lips are distinct and connected with that of the succeeding thecae, except th 1 and th 2 although it may have been obscured in these thecae by overgrowth of cortical tissue. The lip connection is particularly distinctive in the medial and distal parts of the rhabdosome. The λ angle is 30°. The sicula is short and narrow, L is 1.8 mm and apertural W is 0.3 mm. The apex of the sicula reaches the base of th 3. The free part of the sicula is 0.3 mm long. The virgella is short, up to 0.6 mm. In one specimen there is a thickened protrusion in the middle part of the virgella. No sicular rings are observed.

Stratigraphic and geographic range.—Lower Wenlock, C. perneri Biozone , Poland and Lithuania.