Pristiograptus dubius frequens Jaekel, 1889

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 : 600-603

Pristiograptus dubius frequens Jaekel, 1889

Figs. 5M, 11A–C, F–H.

1943 Pristiograptus frequens Jaekel, 1889 ; Přibyl 1943: 24–25, pl. 3:13, text−fig 3A.

1991 Monograptus dubius frequens ( Jaekel, 1889) ; Jaeger 1991: 314, fig. 25: 9, 11, 15.

Material.—More then 50 rhabdosomes and fragments from

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

erratic boulder (S36), Poland and Šiupyliai−69 (994.2– 905.5 m), Kurtuvėnai−161 (1297.1– 127.2 m) boreholes, Lithuania.

Description.—The rhabdosome is narrow and graceful. The proximal end is slightly curved ventrally as far th 5. The ss angle is obtuse. The thecal apertural lip is distinct, not extending onto the ventral wall of the succeeding theca and ending in the beginning of the ventral wall. The number of sicular rings varies from 3 to 8 ( Fig. 11A, B).

Remarks.—The genus Pristiograptus was erected by Jaekel (1889), designating P. frequens as its type species. Recent studies reveal that the differences between P. frequens and P. dubius ( Suess, 1851) are so small, that the former species should be considered as a subspecies of the last mentioned, and earlier established, species by Suess (1851) [compare Jaeger 1991, who used the name Monograptus dubius frequens ( Jaekel, 1889) ]. The difference between P. dubius dubius and P. dubius frequens is in absence of sicular rings in P. dubius dubius and their presence in P. dubius frequens .

Stratigraphic and geographic range.— Colonograptus praedeubeli – Cucullograptus hemiaversus Biozone. P. dubius frequens having been recorded from: Latvia, Lithuania, Poland, Czech Republic, and Germany.