Acta Palaeontologica Polonica

Adaptive radiation of monograptids after the Late Wenlock crisis

Tatyana N.Koren' and Adam Urbanek

Acta Palaeontologica Polonica 39 (2), 1994: 137-167

Succession of late Wenlock graptolites in the Kursala Formation, Tien Shan (Kirghizia), documents of the early recovery phase after the global C. lundgreni Event. Pristiographs dubius was the only survivor among monograptids. After displaying a mass occurrence and an increased variation, the P. dubius stem lineage splits into two main trends: line A, represented by Pristiograptus idoneus and line B, represented by Colonograptus? praedeubeli. The former leads to Lobograptus? sherradae, a generalized forerunner of such diverse trends as linograptids, cucullograptids and possibly also neocucullograptids (via Bohemograptus). The latter initiates the Colonograptus-Saetograptus line. The P. idoneus -
L.? sherrardae lineage shows distinct gracilization, an apomorphic feature, while the other one preserves ancestral robustness, a plesiomorphic character. Hence, the bulk of the later monograptids of Gorstian and Ludfordian age may be derived from ttre P. dubius stem lineage. In respect of this consewative lineage a non-cladistic approach is prefered, because its morphological spectmm and evolutionary potential, and as we believe its specific identity, were preserved, in spite of numerous speciation events, until the early Pridoli.

Key words: global bioevents, C. Lundgreni Event, graptolites, monograptids, adaptive radiation.

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