Representatives of the family Actinostromatidae (Stromatoporoidea) in the Devonian of southern Poland and their ecological significance
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Date
2016-12
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Instytut Geologii UAM
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Abstract
Stromatoporoids of the family Actinostromatidae are common constituents of Givetian to Frasnian (Devonian) or-
ganic buildups. The species-level structure of actinostromatid assemblages from the Devonian of southern Poland is
described in the present paper, with special emphasis on ecological factors that influenced species composition of
the communities. Nine species of the genera Actinostroma and Bifariostroma are distinguished. Members of the family
Actinostromatidae predominated in stromatoporoid assemblages within lower Frasnian carbonate buildup margins.
The most diverse actinostromatid faunas were found within the middle Givetian Stringocephalus Bank, in the upper
Givetian–lower Frasnian biostromal complex and in the lower Frasnian organic buildups. Species-level biodiversi-
ty was lowest within detrital facies which surrounded the Frasnian carbonate buildups. Species of Actinostroma with
well-developed colliculi are commonest within the middle Givetian to early Frasnian coral-stromatoporoid biostromal
complexes, whereas species with strongly reduced colliculi predominate early-middle Frasnian organic buildups. The
skeletal structure of actinostromatids reflects environmental changes, documenting a transition from species with thin,
close-set pillars and widely spaced laminae (common in the middle Givetian) to those with long, thick pillars and meg-
apillars (in Bifariostroma), which were predominant during the early and middle Frasnian. The distribution of growth
forms among species reveals a significant intraspecific variation. Species of Actinostroma can be either tabular or low
domical, depending on the palaeoenvironmental setting. Thus, the present study confirms that stromatoporoid mor-
phology was influenced by environmental conditions.
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Keywords
central Europe, sponges, palaeoecology, palaeoenvironmental variation, intraskeletal variation
Citation
Geologos, 2016, 22, 3, pp. 227-249
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ISBN
ISBN 978-83-232187-4-6
ISSN
ISSN 1426-8981