title: Overcoming the fragility - X-ray computed micro-tomography elucidates brachiopod endoskeletons.
abstract: BACKGROUND
  The calcareous shells of brachiopods offer a wealth of informative characters for taxonomic and phylogenetic investigations. In particular scanning electron microscopy (SEM) has been used for decades to visualise internal structures of the shell. However, to produce informative SEM data, brachiopod shells need to be opened after chemical removal of the soft tissue. This preparation occasionally damages the shell. Additionally, skeletal elements of taxonomic/systematic interest such as calcareous spicules which are loosely embedded in the lophophore and mantle connective tissue become disintegrated during the preparation process.
  
  
  RESULTS
  Using a nondestructive micro-computed tomography (μCT) approach, the entire fragile endoskeleton of brachiopods is documented for the first time. New insights on the structure and position of tissue-bound skeletal elements (spicules) are given as add ons to existing descriptions of brachiopod shell anatomy, thereby enhancing the quality and quantity of informative characters needed for both taxonomic and phylogenetic studies. Here, we present five modern, articulated brachiopods (Rectocalathis schemmgregoryi n. gen., n. sp., Eucalathis sp., Gryphus vitreus, Liothyrella neozelanica and Terebratulina retusa) that were X-rayed using a Phoenix Nanotom XS 180 NF. We provide links to download 3D models of these species, and additional five species with spicules can be accessed in the Supplemental Material. In total, 17 brachiopod genera covering all modern articulated subgroups and 2 inarticulated genera were X-rayed for morphological analysis. Rectocalathis schemmgregoryi n. gen., n. sp. is fully described.
  
  
  CONCLUSIONS
  Micro-CT is an excellent non-destructive tool for investigating calcified structures in the exo- and endoskeletons of brachiopods. With high quality images and interactive 3D models, this study provides a comprehensive description of the profound differences in shell anatomy, facilitates the detection of new delicate morphological characters of the endoskeleton and gives new insights into the body plan of modern brachiopods.
authors: Current address: Max Planck Institute of Colloids and Interfaces, Potsdam-Golm Science Park, Am Mühlenberg 1 OT Golm, 14476 Potsdam, Germany ; Museum für Naturkunde, Leibniz Institute for Evolution and Biodiversity Science, Invalidenstrasse 43, 10115 Berlin, Germany.
authors: Ronald
authors: R
authors: Seidel
authors: Museum für Naturkunde, Leibniz Institute for Evolution and Biodiversity Science, Invalidenstrasse 43, 10115 Berlin, Germany.
authors: Carsten
authors: C
authors: Lüter
keywords: Brachiopoda; Endoskeleton; Interactive 3D model; Micro-computed tomography (μCT); Rectocalathis schemmgregoryi n. gen., n. sp.; Spicules; X-ray
references: Science. 1985 Jun 28;228(4707):1527-8
references: 17831258
references: J Struct Biol. 2009 Jul;167(1):62-7
references: 19341799