Pristiograptus dubius postmagnus, 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 : 608

Pristiograptus dubius postmagnus subsp. nov.

Figs. 5O, 13A–C .

Etymology: From Latin post, after; magnus, great, large.

Holotype: ZPAL G.44/48, rhabdosome with sicula and seven thecae,

Fig. 13 .

Type locality: Mielnik−1 borehole, depth 780.5 m, Poland.

Type horizon: Upper Ludlow, M. (U.) acer Biozone.

Material.—15 rhabdosomes and many fragments from Mielnik borehole (780.5 m), Poland.

Diagnosis.—Distinct thecal lips connecting with those of the succeeding thecae. Sicula with three rings.

Description.—The rhabdosome is robust and the proximal end is slightly curved ventrally up to th 5. The longest rhabdosome L is more than 15 mm long. The rhabdosome W from 0.65 mm at th 1, to 0.8 mm at th 2, 9 mm at th 3, 1 mm at th 4, 1.1 mm at th 5, 1.2 mm at th 6. The Wmax is 1.3 mm. The interapertural width is 0.55 mm at th 1, 0.65 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. The ss angle is obtuse. Th 1 is 1mm long and 0.3 mm wide. The free part of each theca is half of its whole length. The thecal lips are distinct and connected with the lip of the succeeding thecae ( Figs. 5O, 13A–C ). The lip connection is particularly well developed in the medial and distal parts of the rhabdosome. The λ angle is 30°. The sicula is short and narrow. Its L is 1.8 mm and apertural W is 0.3 mm. The apex of the sicula reaches the base of th 3. The sicula has three rings. The virgella is short, up to 0.5 mm.

Remarks.— P. dubius postmagnus subsp. nov. is similar to P. dubius magnus subsp. nov., in the connection of the lip with the succeeding thecal lip. In contrast to P. dubius magnus subsp. nov. it has sicular rings.

Stratigraphic and geographic range.— M. (U.) acer Biozone , Upper Ludlow, Poland.

Figures

Fig. 13. SEM micrographs of Ludfordian graptolites Pristiograptus dubius postmagnus subsp. nov. and Pristiograptus dubius labiatus Urbanek, 1997. A–C. Pristiograptus dubius postmagnus subsp. nov., Mielnik−1 borehole, Poland, depth 780.5 m; Monograptus (Uncinatograptus) acer Biozone. A. ZPAL G.44/48, lateral view of rhabdosome (A1), the thecal lip with connection to the succeeding theca (A2), and proximal end of rhabdosome (A3). B. ZPAL G.44/49, lateral view of rhabdosome sicula with rings (B1) and proximal end of rhabdosome (B2). C. ZPAL G.44/50, medial part of rhabdosome (C2), enlargements showing connections to the succeeding thecae (C1, C3). D–F. Pristiograptus dubius labiatus Urbanek, 1997, Mielnik−1 borehole, Poland, depth 753.3 m; Monograptus (Uncinatograptus) spineus–Neocolonograptus parultimus Interzone. D. ZPAL G.44/51, general view of rhabdosome (D1), sicula with two first thecae and depression on th1 lip (D). E. ZPAL G.44/52, lateral view of rhabdosome (E) and proximal end of rhabdosome (E). F. ZPAL 2 1 2 G.44/53, lateral view of rhabdosome (F1) enlargement of proximal end (F2).