Carbon and oxygen isotope fractionation in the Late Devonian heterocoral Oligophylloides: Implications for the skeletogenesis and evolution of the Heterocorallia

The order Heterocorallia is an enigmatic, anatomically distinct group of calcifying Palaeozoic corals with unclear affinities to other, either extinct or modern cnidarian lineages. Here, we present results microstructure and stable isotope studies on exceptionally well-preserved skeletons two species the heterocoral Oligophylloides from Famennian (Upper Devonian) Anti-Atlas, Morocco Holy Cross Mountains, Poland. investigations provide new information skeletogenesis fractionation effects in heterocorals. In estimate possible role diagenetic alteration observed carbon oxygen ratios, have conducted several preservation tests, including transmitted-light, scanning-electron, fluorescence cathodoluminescence microscopy, Raman spectroscopy, trace element analyses. least- most-altered skeleton portions identified based this approach are typified by clearly different isotopic signatures. least-altered parts specimens reveal ratios close those contemporaneous marine-equilibrated calcites. moderately-pronounced, positive correlations between δ13C δ18O values for these coralla may reflect relatively minor vital effects, obscured some degree overprint. suggest that mechanisms heterocorals differed markedly significant kinetic characteristic scleractinian corals. Rather, moderate, if any, extent non-equilibrium during resembled typical, environmental metabolic CO2-dominated shown most other marine calcifiers. These include rugose corals, hydrocorals and, particular, octocorals, which show notable architectural structural similarities.