A modern scleractinian coral with a two-component calcite–aragonite skeleton

Jarosław Stolarski*, Ismael Coronado, Jack G. Murphy, Marcelo V. Kitahara, Katarzyna Janiszewska, Maciej Mazur, Anne M. Gothmann, Anne Sophie Bouvier, Johanna Marin-Carbonne, Michelle L. Taylor, Andrea M. Quattrini, Catherine S. McFadden, John A. Higgins, Laura F. Robinson, Anders Meibom

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

5 Citations (Scopus)


One of the most conserved traits in the evolution of biomineralizing organisms is the taxon-specific selection of skeletal minerals. All modern scleractinian corals are thought to produce skeletons exclusively of the calcium-carbonate polymorph aragonite. Despite strong fluctuations in ocean chemistry (notably the Mg/Ca ratio), this feature is believed to be conserved throughout the coral fossil record, spanning more than 240 million years. Only one example, the Cretaceous scleractinian coral Coelosmilia (ca. 70 to 65 Ma), is thought to have produced a calcitic skeleton. Here, we report that the modern asymbiotic scleractinian coral Paraconotrochus antarcticus living in the Southern Ocean forms a two-component carbonate skeleton, with an inner structure made of high-Mg calcite and an outer structure composed of aragonite. P. antarcticus and Cretaceous Coelosmilia skeletons share a unique microstructure indicating a close phylogenetic relationship, consistent with the early divergence of P. antarcticus within the Vacatina (i.e., Robusta) clade, estimated to have occurred in the Mesozoic (ca. 116 Mya). Scleractinian corals thus join the group of marine organisms capable of forming bimineralic structures, which requires a highly controlled biomineralization mechanism; this capability dates back at least 100 My. Due to its relatively prolonged isolation, the Southern Ocean stands out as a repository for extant marine organisms with ancient traits.

Original languageEnglish
Article numbere2013316117
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number3
Publication statusPublished - 19 Jan 2021

Bibliographical note

Funding Information:
ACKNOWLEDGMENTS. This work was funded in part by the National Science Centre (Poland) research grant 2017/25/B/ST10/02221 to J.S. and by a European Research Council Advanced Grant number 788752 (UltraPal) to A.M. M.V.K. is supported by the São Paulo Research Foundation (Fundação de Amparo à Pesquisa do Estado de São Paulo 2014/01332-0 and 2017/50229-5) and National Science Council (Conselho Nacional de Desenvolvimento Científico e Tecnológico 301436/2018-5). L.F.R. and M.L.T. were supported by the UK Natural Environment Research Council NE/R005117/1. The RRS James Clark Ross JR15005 cruise was part of the Biodiversity, Evolution, and Adaptation team of the Environmental Change and Evolution Programme at British Antarctic Survey. Funding of the mitogenome of P. antarcticus was provided by the NSF (1457817 to C.S.M. and 1457581 to E. Rodriguez). The work was also partially supported by the European Union within the European Regional Development Fund, through the Innovative Economy Operational Program POIG.02.02.00-00-025/09 (NanoFun).

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© 2021 National Academy of Sciences. All rights reserved.


  • Biomineralization
  • Calcium carbonate
  • Evolution
  • Scleractinian corals
  • Southern Ocean


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