Mikołaj K. Zapalski

Evidence of photosymbiosis in Palaeozoic tabulate corals

Coral reefs form the most diverse of all marine ecosystems on the Earth. Corals are among their main components and owe their bioconstructing abilities to a symbiosis with algae (Symbiodinium). The coral–algae symbiosis had been traced back to the Triassic (ca 240 Ma). Modern reef-building corals (Scleractinia) appeared after the Permian–Triassic crisis; in the Palaeozoic, some of the main reef constructors were extinct tabulate corals. The calcium carbonate secreted by extant photosymbiotic corals bears characteristic isotope (C and O) signatures. The analysis of tabulate corals belonging to four orders (Favositida, Heliolitida, Syringoporida and Auloporida) from Silurian to Permian strata of Europe and Africa shows these characteristic carbon and oxygen stable isotope signatures. The δ18O to δ13C ratios in recent photosymbiotic scleractinians are very similar to those of Palaeozoic tabulates, thus providing strong evidence of such symbioses as early as the Middle Silurian (ca 430 Ma). Corals in Palaeozoic reefs used the same cellular mechanisms for carbonate secretion as recent reefs, and thus contributed to reef formation.

Brachiopods and Their Auloporid Epibionts in the Devonian of Boulonnais (France): Comparison with Other Associations Globally

From research undertaken on brachiopods encrusted by auloporids at two intervals in the Frasnian (Beaulieu and Ferques Formations) of Boulonnais (France), we conclude that the most important factors influencing encrustation were usually (in decreasing order): size of the host, morphology, feeding currents, shell orientation in vivo and shell ornament. Shell structure (punctate or impunctate) seems not to have influenced the rate of encrustation. In the cases discussed, most but not all auloporids encrusted their hosts in vivo. The most favourable environments for development of both brachiopods and epibionts seem to have been hard bottoms and thin limestone beds alternating with argillaceous beds. The influence of environmental (sedimentologic) conditions is difficult to precisely specify in terms of the development of encrustation, but seems to have played an important role.

Tabulate Corals after the Frasnian/Famennian Crisis: A Unique Fauna from the Holy Cross Mountains, Poland

Famennian tabulate corals were very rare worldwide, and their biodiversity was relatively low. Here we report a unique tabulate fauna from the mid- and late Famennian of the western part of the Holy Cross Mountains (Kowala and Ostrówka), Poland. We describe eight species (four of them new, namely ?Michelinia vinni sp. nov., Thamnoptychia mistiaeni sp. nov., Syringopora kowalensis sp. nov. and Syringopora hilarowiczi sp. nov.); the whole fauna consists of ten species (two others described in previous papers). These corals form two assemblages—the lower, mid-Famennian with Thamnoptychia and the upper, late Famennian with representatives of genera ?Michelinia, Favosites, Syringopora and ?Yavorskia. The Famennian tabulates from Kowala represent the richest Famennian assemblage appearing after the F/F crisis (these faunas appear some 10 Ma after the extinction event). Corals described here most probably inhabited deeper water settings, near the limit between euphotic and disphotic zones or slightly above. At generic level, these faunas show similarities to other Devonian and Carboniferous faunas, which might suggest their ancestry to at least several Carboniferous lineages. Tabulate faunas described here represent new recruits (the basin of the Holy Cross mountains was not a refuge during the F/F crisis) and have no direct evolutionary linkage to Frasnian faunas from Kowala. The colonization of the seafloor took place in two separate steps: first was monospecific assemblage of Thamnoptychia, and later came the diversified Favosites-Syringopora-Michelinia fauna.

A new Silurian Avicenia (Tabulata): taxonomy, growth pattern and colony integration

ABSTRACT A new heliolitid tabulate coral Avicenia kocyani n. sp. is described from Silurian erratic boulders from Pomerania (Poland). The new species has higher intracolonial variation than other heliolitids. The growth pattern in corallites of the new species is not correlated with the growth pattern in coenenchymal tubes. This phenomenon is probably caused by different gene expressions in corallites and common tissue. Coenenchymal corals with a common skeleton, developed as polygonal tubes may have two levels of colonial integration: lower, with uncoordinated growth of corallites and common tissue (as for example in Avicenia kocyani n. sp.) and higher, with a unified growth pattern throughout the colony (as for example in Heliolites diligensis Bondarenko, 1966). Heliolitids are known to show strong provincialism during the Silurian. The discovery of Avicenia Leleshus, 1974 in Europe (previously known only from Central Asia) shows that at least some of them had a wider distribution than previously thought.

Estimation of palaeoenvironmental changes: can analysis of distribution of tabulae in tabulates be a tool?

Abstract Growth periodicity (cyclomorphic variation) in corals is expressed by various features, among them changes in the distribution of tabulae. A method potentially useful in analysis of periodical environmental changes is proposed herein. Measurement of spaces between tabulae in tabulate corals and preparation of a histogram converted into a trend curve may show relative periodical fluctuations of the environment. Such an analysis, exemplified here on Givetian Pachyfavosites sp. from the Avesnois (northern France), shows that this method may be used as a tool for estimation of environmental changes.

New Famennian colonial coral (Rugosa) from the Holy Cross Mountains (Poland): an example of local evolution after Frasnian-Famennian extinction.

Colonial rugose corals are extremely rare in the fossil record after the Late Devonian (Frasnian-Famennian) extinction event. Here, we report a new genus and species, Famastraea catenata, from the late Famennian of the western part of the Holy Cross Mountains (Kowala) in Poland. Although this taxon is colonial, it displays many morphological characters very close to the typically late Famennian solitary species Palaeosmilia aquisgranensis (Frech, 1885), described earlier from the same locality. Hence, we postulate that F. catenata is derived from P. aquisgranensis. In contrast to other Famennian colonial rugose corals, the new taxon represents an example of local evolution within the group of so-called ‘Strunian’ corals. Consequently, we postulate that the new taxon represents a new colonial rugose fauna, which, however, did not survive the subsequent Late Devonian crisis (i.e. Hangenberg event). F. catenata most probably inhabited deeper water settings, possibly near the boundary between the euphotic and dysphotic zones, as inferred from many other benthic taxa described from this locality.

Enigmatic Fossils from the Lower Carboniferous Shrimp Bed, Granton, Scotland

The Lower Carboniferous (Visean) Granton Lagerstätte (Edinburgh, Scotland) is principally known for the discovery of the conodont animal, but has also yielded numerous crustaceans and other faunas. Here we report on small branching colonies, reaching 10 mm in length. They are small, erect, arborescent, and irregularly branched with predominant monopodial and dichotomous growth. They bud in a single plane. In one specimen the wall microstructure is well preserved and it is composed of evenly spaced, linear fibers, running parallel to the axis of the stems, and connected by transverse bars. We discuss possible biological affinities of these organisms; we consider algal, poriferan, hydrozoan and bryozoan affinities. The general pattern of branching, presence of fan-like structures (interpreted here as possible gonophores) and microstructure suggests affinity to Hydrozoa, affinity to non-calcifying algae is less likely. Assuming hydrozoan nature; the microstructure might suggest affinities with the extant family Solanderiidae Marshall, 1892 that possess an internal chitinous skeleton. The EDS analysis shows that fossils discussed here are preserved as phosphates. The skeletons were probably not mineralized, the presence of phosphorus suggests that the colonies were originally composed of chitin. We describe these organisms as Caledonicratis caridum gen. et sp. nov. (Solanderiidae?, Capitata?). Colonies of C. caridum gen et. sp. nov. sometimes encrust the exuviae of crustaceans, which very probably lived in fresh to brackish water thus indicating a likely habitat of Caledonicratis.