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Data from: Reinvestigation of the type specimen of Ginkgophyllum grasseti Saporta 1875 using Reflectance Transforming Imaging

Citation

Decombeix, Anne-Laure; Escapa, Ignacio H.; De Franceschi, Dario; Béthoux, Olivier (2021), Data from: Reinvestigation of the type specimen of Ginkgophyllum grasseti Saporta 1875 using Reflectance Transforming Imaging, Dryad, Dataset, https://doi.org/10.5061/dryad.np5hqbzsx

Abstract

Reflectance Transforming Imaging (RTI) produces photographs in which the angle of the light can be changed at will, allowing to investigate remotely minute details of the 3D structure of sub-planar objects. Here we apply this technique to the type specimen of Gingkophyllum grasseti, a vegetative shoot with putative ginkgophyte affinities from the early Permian of Lodève (France). Gingkophyllum grasseti, the type species of the corresponding genus, was originally described by Saporta in 1875 and has never been illustrated other than by drawings representing only portions of the shoot. Using RTI, we describe and illustrate the specimen and discuss some key features, such as the arrangement of the leaves on the shoot or the presence of abundant secretory structures. Through a historical account, we show how the lack of illustration led to confusions about the morphology of Ginkgophyllum and we discuss the importance of reinvestigating type specimens of Paleozoic ginkgophyte taxa in order to clarify their taxonomy and better understand their evolutionary history. The sharing of RTI files is one example of approaches that can be further developed to improve remote access to specimens.

Methods

This dataset contains nine RTI files (RTI a-i) from which were extracted images reproduced on Plates II-V (except for Plate IV, 3, 4), and two multi-layered psd files, namely 'Plate IV 3 working document (RTI c).psd' and 'Plate IV 4 working document (RTI d).psd', containing several snapshots extrated from RTI c and RTI d, respectively, and processed to obtain the images reproduced on Plate IV, 3, 4.

Individual sets of photographs used to process  RTI files were taken using a Canon EOS 5D Mark III digital camera equipped with a Canon 100 mm macro lens (RTI a, b, e-h), a Canon 50 mm macro lens (RTI c, d) or a Canon MP-E 65 mm macro lens (RTI i) (all Tokyo, Japan). A 28-cm diameter light dome equipped with 54 LEDs (distributed over three rings) was used as illumination source, and automation of camera triggering and of changes in illumination were performed using the dedicated control box. Illumination reference was given by a black reflecting sphere placed aside the area of interest and cropped out during RTI processing (light dome, control box and reflecting sphere, FlyDome, Paris, France). All LEDs were used for RTI a-h (i.e. each set is composed of 54 photographs) but only a subset was used for RTI i (specifically, half of the LEDs of the two lower LED rings, i.e. 21 LEDs). Photographs of a given set were batch-processed using Adobe Photoshop (Adobe Systems, San Jose, CA, USA) to optimize focus and for adding legend and scale bar. RTI files were then computed using the RTIbuilder software (Cultural Heritage Imaging, San Francisco, CA, USA).

The document 'Plate IV 3 working document (RTI c).psd' is based on four snapshots (light source coordinates: X:0.00, Y:0.00; X:-0.20, Y:0.50; X:0.00, Y:0.65; X:0.50, Y:0.60) combined using the ‘overlay’ blending mode, with further adjustments that can be appreciated using the layers panel. The document 'Plate IV 4 working document (RTI c).psd' is based on three snapshots (light source coordinates: X:-0.50, Y:0.75; X:-0.15, Y:0.65; X:0.50, Y:0.50) combined using the ‘multiply’ blending mode, with further adjustments that can be appreciated using the layers panel.

Usage Notes

The RTI files can be opened using the software RTIviewer (Cultural Heritage Imaging, San Francisco, CA, USA). The psd file can be opened using the software Adobe Photoshop (Adobe Systems, San Jose, CA, USA).

Funding

Agence Nationale de la Recherche, Award: ANR-11-INBS-0004-RECOLNAT