Abstract
Recent mesophotic coral ecosystems (MCE) occur at depths between 30 and 150 m and are characterized by dominance of platy corals. Such morphology is an effect of specific adaptation to efficient light harvesting. Here, we describe and analyze platy coral assemblages from two Middle Devonian localities in the Holy Cross Mountains (Poland) that during this time were located on the southern shelf of Laurussia at tropical latitudes. The Eifelian argillaceous sediments of Skały are dominated by platy and encrusting tabulate corals (Roseoporella, Platyaxum and Alveolites). Coeval faunas from the shallow-water parts of the Holy Cross Mountains basin display bulbous and branching morphology, thus indicating a Paleozoic coral zonation similar to that known in the Recent. Hence, the Skały site seems to be the oldest known MCE (ca. 390 Ma). A Givetian biostrome from Laskowa Quarry is a second example dominated by platy corals, with abundant branching forms; this site can be recognized as another Devonian MCE. Frondescent Platyaxum, common at both sites, had a growth habit similar to that of Recent Leptoseris, Mycedium or Pavona. Platy morphology is photoadaptive and may evidence photosymbiosis in tabulate (Alveolites, Roseoporella, Platyaxum) and rugose corals (Phillipsastrea). Furthermore, it may serve as a tool for recognition of the lower euphotic zone in the fossil record.
Highlights
Recent mesophotic coral ecosystems (MCE) occur at depths between 30 and 150 m and are characterized by dominance of platy corals
We describe and analyze platy coral assemblages from two Middle Devonian localities in the Holy Cross Mountains (Poland) that during this time were located on the southern shelf of Laurussia at tropical latitudes
Coeval faunas from the shallowwater parts of the Holy Cross Mountains basin display bulbous and branching morphology, indicating a Paleozoic coral zonation similar to that known in the Recent
Summary
Recent mesophotic coral ecosystems (MCE) occur at depths between 30 and 150 m and are characterized by dominance of platy corals. Such morphology is an effect of specific adaptation to efficient light harvesting. The best adaptations to depleted light are shown by platy corals (e.g., Kuhlmann 1983; Kahng et al 2010). MCEs are dominated by platy or encrusting corals, and such a morphology is broadly considered as photoadaptive growth (e.g., Graus and Macintyre 1976, 1982; Rosen et al 2002; Anthony and Hoegh-Guldberg 2003; Kahng et al 2010, 2012, 2014). Scleractinian corals, massively appeared in the Triassic (ca. 245 Ma); large Paleozoic ‘‘reefs’’ were built with contribution from rugose and tabulate corals that became extinct by the end of Permian (ca. 250 Ma)
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