Functional consequences of Palaeozoic reef collapse

Biogenic reefs have been hotspots of biodiversity and evolutionary novelty throughout the Phanerozoic. The largest reef systems in Earth’s history occurred in the Devonian period, but collapsed during the Late Devonian Mass Extinction. However, the consequences for the functional diversity of Palaeozoic reefs have received little attention. Here, we examine changes in the functional diversity of tabulate coral assemblages over a 35 million year period from the middle Devonian to the Carboniferous, straddling the multiphase extinction event to identify the causes and ecological consequences of the extinction for tabulate corals. By examining five key morphological traits, we show a divergent response of taxonomic and functional diversity to the mass extinction: taxonomic richness peaked during the Givetian (~ 388–383 Ma) and coincided with peak reef building, but functional diversity was only moderate because many species had very similar trait combinations. The collapse of taxonomic diversity and reef building in the late Devonian had minimal impact on functional richness of coral assemblages. However, non-random shifts towards species with larger corallites and lower colony integration suggest a shift from photosymbiotic to asymbiotic taxa associated over the study period. Our results suggest that the collapse of the huge Devonian reef systems was correlated with a breakdown of photosymbiosis and extinction of photosymbiotic tabulate coral taxa. Despite the appearance of new tabulate coral species over the next 35 million years, the extinction of taxa with photosymbiotic traits had long-lasting consequences for reef building and, by extension, shallow marine ecosystems in the Palaeozoic

Parasitism versus commensalism: the case of Tabulate endobionts

International audienceTube-like traces of organisms belonging to the ichnogenus Chaetosalpinx Sokolov have been considered in the literature as commensal endobiontic organisms of tabulate corals. Their position between the corallites (or sometimes within the septa), perforation of the host's skeleton and soft tissue, modification of its phenotype and a possible inhibition of its growth show that the relationship between these organisms and tabulate corals can best be interpreted as parasitism rather than commensalism, as previously suggested. Such an interpretation may be extended to the ichnogenera Helicosalpinx Oekentorp and Actinosalpinx Sokolov, which show identical placement within the host colony and similar features, such as the absence of their own wall

Estimation of the palaeoenvironvental changes: can analysis of distribution of tabulae in tabulates be a tool? In ALVARO J.J., Aretz M., Boulvain F., Münnecke A., VACHARD D. & Vennin E. (eds), Palaeozoic Reefs and Bioaccumulations: Climatic and Evolutionary Controls.

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The palaeobiodiversity of stromatoporoids, tabulates and brachiopods in the Devonian of the Ardennes - Changes throuh time

The specific biodiversity of stromatoporoids, tabulates and brachiopods from the Ardennes (707 taxa) has been analyzed stage-by-stage from the Lochkovian up to the Famennian. The diversity of each group may be correlated with external factors (e.g. facies), but it varied individually (e.g. decline of brachiopods in the Givetian). The faunas are discussed at the order level, however some more diversified orders are analyzed at family level. Biodiversity shows a sinle peak centered on the Givetian for the bioconstructors, and two major peaks (Emsian-Eifelian and Frasnian) for the brachiopods. The most diversified orders are Stromatoporellida (stromatoporoids), Favositida (tabulate corals) and Spiriferida (brachiopods). Stromatoporoids display two, tabulate corals four and brachiopods five stages of renewal of fauna

Selected benthic faunas from the Devonian of the Ardennes: an estimation of palaeobiodiversity

2 fig., 2 tabl.A survey of the principal benthic faunas from the Devonian of the Ardennes is presented. The -diversity is very high (707 species, including 138 species of stromatoporoids, 113 species of tabulates, hydroids and chaetetids, and 456 species of brachiopods). Analysis of their distribution through time indicates two brachiopod diversity peaks (Emsian/Eifelian and Frasnian), a single stromatoporoid diversity peak (Givetian), and no clear peak of tabulate corals (with the highest diversification during the Eifelian-Frasnian). The highest diversity of bioconstructors in the Givetian correlates with a decrease in brachiopod diversity. Changes in the vertical distribution of the faunas are correlated with the facies development: the development of carbonates correslates with the abundance of stromatoporoids and tabulates, while brachiopods were most abundant before and after the peak of carbonate development. Bioconstructors are absent (or nearly absent) in siliciclastic facies

The palaeobiodiversity of stromatoporoids, tabulates and brachiopods in the Devonian of Ardennes — Changes through time

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La Vie en Ardenne occidentale au Paléozoïque supérieur (Dévonien-Carbonifère, -416 à -299 Ma) : paléobiodiversité, événements paléobiologiques, paléoenvironnements, paléobiogéographie

The Ardenne Massif is part of a complex of Palaeozoic outcrops between the Channel in the west and the Rhine river and beyond in the east. It has registered both the Caledonian and the hercynian orogenies. Originally part of a terrane located north of the Gondwana supercontinent (Avalonia), it became an element f the southern margin of the Old Red Sandstone Continent (ORSC, also called Euramerica, Laureuropa, or Laurussia) in the Devonian and Carboniferous, when it suffered the effects of the Hercynian orogeny by collision of the ORSC and Gondwana. These global tectonic events, linked to climatic changes due to continental dirft, had profound consequences on the living organisms of the Ardenne Massif. Here we focus on some aspects of a series of animal groups of western Ardenne, being elements of either the benthos (brachiopods, trilobites), or the reefal environments (tabulate corals, stromatopores), or the nekton (vertebrates, including the first tetrapods). When vertebrates ("fishes") and brachiopods were quite abundant as early as the base of the Devonian, mortly in siliciclastic facies, reefal organisms appear only in the Emsian, and become abundant in the Eifelian, with the development of a carbonate platform. Reefs or reef-like buildings occur up to the Early Carboniferous, where new fish assemblages are known. Trilobites occur often with brachiopod-bearing communities. The trilobite-rich locality of the "Mur des Douaniers", at the former French/Belgian boundary, is an example of an early Eifelian Fossil-Lagerstatte, now protected as a Nature Reserve