Adam URBANEK
In: Urbanek, A. & Teller, L. (eds.), Silurian Graptolite Faunas in the East European Platform: Stratigraphy and Evolution.
Palaeontologia Polonica 1997, 56, 87-231
Graptolites etched from the Mielnik 1 wellcore (E Poland) reveal the main features of the
development of monograptid faunas within the late Ludfordian - early Pridoli interval. Fifteen
species and subspecies are described and Monograptus (Slovinograptus) subgen. n. as well as
Neocolonograptus gen. n. are erected. Morphology of many species has been described
adequately for the first time and their systematic position corrected. Four graptolite zones of
the late Ludfordian are distinguished. The late Ludfordian fauna, which appears after the
kozlowskii Event, is composed mainly of immigrants dominated by hooded monograptids. They
reappear as a result of the Lazarus effect. Some of them initiated the lobate spinose phyletic
line terminating with Monograptus (Uncinatograptus) spineus, a highly characteristic index
species. The lobate and the lobate spinose types are accompanied by bilobate forms
(Pseudomonoclimacis latilobus). The graptolite sequence indicates that the appearance of the
early Pridoli fauna was preceded by a biotic crisis, namely the spineus Event. Therefore this
fauna is made up of a few holdovers and some new elements which developed from Pristiograptus
dubius stem lineage (Neocolonograptus gen. n., Istrograptus Tsegelnjuk). This early assemblage,
composed of bilobate forms, was later enriched by hooded monograptids, reappearing after the
spineus Event. Both the late Ludfordian and early Pridoli assemblages abound in instances of
homeomorphy and generic transitions. The latter occur due to independent acquisition by some
forms of simple thecal characters which allows their assignement to a new genus. Another
remarkable feature of Late Silurian monograptids is reduction in the number of sicular rings,
and establishing of a steady relation between one of the rings and the virgella. This character
state was independently achieved as a structural grade, by all, otherwise unrelated, phyletic
lines of Late Silurian monograptids.
Key words: Late Silurian, graptolites, monograptids, stratigraphy, taxonomy, biotic crises,
oligophyly, homeomorphy, adaptive repetitions, anagenesis.
Adam Urbanek, Instytut Paleobiologii PAN, ul. Twarda 51/55, 00 818 Warszawa, Poland. urbanek@twarda.pan.pl
was established by Zakład Paleobiologii in 2002
It is edited and periodacally updated by
Piotr Mierzejewski, Count of Calmont & Countess Maja Korwin-Kossakowska
