Acta Palaeontologica Polonica

Ecology, evolution, distribution and population of Hexagonaria in Western Europe

Hsien Ho Tsien

Acta Palaeontologica Polonica 25 (3-4), 1980: 633-644

The record of Hexagonarta in the Lower and Middle Devonian shows that only slow rates of change occurred at these times, whereas in Frasnian time there occurred complex diversity and speciation patterns. Very rapid faunal changes and mass extinctions in corals have been observed near the boundary of Middle Devonian and Upper Devonian and at the end of Fr 1 time. Based on the study of population variation, ecological variation and phylogenetic lineage, the complete evolutionary patterns of Hexagonaria can be traced in the Givetian and Frasnian. The evolutionary patterns observed in different facies demonstrate that: 1. most changes in diversity and speciation were strictly related to differences in the bioiogy of species adapted to different or changing environments, 2. the critical factors in encouraging diverSification of species appear to be a combination of ecologic conditions and paleogeographic situations, 3. some parallel evolutions were independent of environments and paieogeographic isolation but were due to time.

Key words: Corais, Rugosa, evoiution, population variation, ecological variation, Upper Devonian, Europe.

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