Abstract
Biological hard tissues are a rich source of design concepts for the generation of advanced materials. They represent the most important library of information on the evolution of life and its environmental conditions. Organisms produce soft and hard tissues in a bottom-up process, a construction principle that is intrinsic to biologically secreted materials. This process emerged early on in the geological record, with the onset of biological mineralization. The phylum Brachiopoda is a marine animal group that has an excellent and continuous fossil record from the early Cambrian to the Recent. Throughout this time interval, the Brachiopoda secreted phosphate and carbonate shells and populated many and highly diverse marine habitats. This required great flexibility in the adaptation of soft and hard tissues to the different marine environments and living conditions. This review presents, juxtaposes and discusses the main modes of mineral and biopolymer organization in Recent, carbonate shell-producing, brachiopods. We describe shell tissue characteristics for taxa of the orders Rhynchonellida, Terebratulida, Thecideida and Craniida. We highlight modes of calcite and organic matrix assembly at the macro-, micro-, and nano-scales based on results obtained by Electron Backscatter Diffraction, Atomic Force Microscopy, Field Emission Scanning Electron Microscopy and Scanning Transmission Electron Microscopy. We show variation in composite hard tissue organization for taxa with different lifestyles, visualize nanometer-scale calcite assemblies for rhynchonellide and terebratulide fibers, highlight thecideide shell microstructure, texture and chemistry characteristics, and discuss the feasibility to use thecideide shells as archives of proxies for paleoenvironment and paleoclimate reconstructions.
Highlights
Brachiopods are bi-valved lophophorates and form a group of marine sessile organisms that secrete either phosphatic (Linguliformea) or calcitic (Craniiformea, Rhynchonelliformea) shells
We investigated twenty Recent brachiopod taxa (Table S1): two rhynchonellide, one craniide, three thecideide and fourteen terebratulide species and base our results and conclusions on Electron Backscatter Diffraction Measurements (EBSD), complemented by Atomic Force Microscopy (AFM), Scanning Transmission Electron Microscopy (STEM) and FE-SEM imaging of fractured and etched shell cross-sectional surfaces and geochemical results obtained by Ion Microprobe and LAICP-MS analyses
EBSD band-contrast images highlight the distinctness and diversity of biocrystal shapes, sizes and microstructures that we observe in Recent rhynchonellide and terebratulide (Fig. 1), thecideide (Fig. 2A), and craniide (Fig. 2B) brachiopod shells
Summary
Laboratoire des Sciences du Climat et de l’Environnement, LSCE, Gif sur Yvette, France. Department of Earth Sciences, Brock University, St. Catharines, ON L2S 3A1, Canada. Centre for Coastal Studies, University of New Brunswick, Saint John, NB E2L 4L5, Canada
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have