Material and methods
The following specimens were used for testing the methods described below; for stratigraphy of the lithographic limestones of southern Germany see
Two specimens, possibly representing juveniles of Cancrinos claviger
Münster, 1839 (Figures 1.1–3,
4.1–4); found near Öchselberg (Solnhofen Lithographic Limestones, Upper Kimmeridgian, Beckeri Zone, Ulmense Subzone) resp. Langenaltheim (Solnhofen Lithographic Limestones, Lower Tithonian, Hybonotum Zone, Rueppellianus Subzone); private collection of Matthias Wulf, Rödelsee;
One specimen of Sculda spinosa
Kunth, 1870, preserved with part and counterpart (Figure 1.4–6); found in the Nusplingen Lithographic Limestone (Upper Kimmeridgian, Beckeri Zone, Ulmense Subzone); collection of the Staatliches Museum für Naturkunde, Stuttgart (SMNS 63997/1);
One specimen of ?Sculda sp. (Figure 2) from the Upper Cretaceous (Cenomanian) of Hadjoula, Lebanon; private collection of two of the authors (CH & JTH);
One specimen of Sculda pennata
Münster, 1840 (Figure 3); found near Zandt (Solnhofen Lithographic Limestones, Lower Tithonian, Hybonotum Zone, Riedense Subzone); collection of the Staatliches Museum für Naturkunde, Stuttgart (SMNS 67505);
One specimen of Antrimpos sp. (Figure 4.6–8); found near Solnhofen (Solnhofen Lithographic Limestones, Lower Tithonian, Hybonotum Zone, Rueppellianus Subzone); private collection of one of the authors (RF);
One specimen of an undetermined caridean shrimp; found near Eichstätt (Solnhofen Lithographic Limestones, Lower Tithonian, Hybonotum Zone, Riedense Subzone); private collection of one of the authors (RF).
General settings: Specimens were documented exhaustively under high resolution. As the specimen is larger than the field of view, several overlapping images are taken to document the complete specimen in an x- and y-axis. Each single area was documented not with a single image, but with a stack of images, i.e., a number of images with a shifting plane of focus in the z-axis. The images of each stack were fused with the freely available image fusion software CombineZM. These resulting images were then combined in the x- and y-axis, partially automated via the photomerge function and/or by hand in Photoshop and the freely available software program GIMP. The result is a high-resolution composite image. The exact number of images for each specimen and applied light setting are given in
Specifically, we used three different types of light:
Normal light: Two possible specimens of Cancrinos claviger and one of ?Sculda sp. were documented under a Leica stereomicroscope with a mounted DCM 500 ocular camera. For homogenous lighting a ring lamp was used. To produce stacks the camera was set to take an image every two seconds, while the focus was progressively shifted manually.
Ultraviolet: The smaller of the two specimens of Cancrinos claviger and additionally a specimen of Sculda spinosa (part and counterpart) were documented under UV light (358 nm) on an Axio Scope 2 with a mounted Axiocam.
Green light: A specimen of Sculda pennata and a specimen of ?Sculda sp. were both documented under green light (546 nm). All other settings were the same as for the documentation with UV light.
Combining UV-fluorescence images of part and counterpart: Part and counterpart of the specimen of Sculda spinosa (see above) were digitally combined. All black areas on the counterpart were set as transparent using the magic wand tool in Adobe Photoshop (CS3). The composite image of the counterpart was then mirrored and placed above the composite image of the part (terms 'part' and 'counterpart' are exchangeable in this special specimen as it is extremely flattened and both parts contain a lot of substance of the fossil; in general it would be useful to leave the part with more substance unaltered while processing the other one with transparency).
Combining normal light images with a UV-fluorescence image of the same specimen: The composite images of the smaller of the two specimens of Cancrinos claviger, one under normal light, one under
UV light, were combined into a single image. For this purpose, the image under normal light was inverted, and all parts not assignable to the fossil were set transparent. The resulting image was placed on the
Confocal laser scanning microscopy (cLSM): Details of the specimen of ?Sculda sp. were documented under a Leica cLSM. The excitation wavelength was set to a range of 488–543 nm. In total the stack was made up of 43 images. The resulting stack of images was further processed using the freely available software program ImageJ, where the 'find edges' function was used to enhance contrast. The resulting stack was 3D-projected (Maximum Intensity Projection, MIP) using the freely available DICOM-viewer
Stereo images and 3D models via Structure from Motion (SFM): The pleon of the larger possible specimen of Cancrinos claviger was documented as a stereo image, produced with a tiltable Zeiss Stemi 1000 stereomicroscope with a mounted DCM 500 ocular camera (tilting of about 6°). The images were then loaded into the freely available test version software "Structure from Motion" (MeeSoft) (for principles of this method see
Dellaert et al. 2000). Five reference points were assigned, i.e., corresponding structures on the two single images of the stereo image were marked. Based on this, a 3D model was calculated.
Computer tomography (CT) scans: A large uncompressed specimen of Antrimpos sp. was scanned in a medical CT-scanner (Philips Brilliance iCT 256) under the setting for small structures (resolution of 0.667 mm) for very heavy patients to enhance the emitted energy. The resulting stack of 402 images was processed using the freely available DICOM-viewer OsiriX (volume rendering).
The specimen of ?Sculda sp. and the specimen of an undetermined caridean shrimp were put into the SEM (ZEISS DSM 962) and their elemental composition analysed using a mounted energy dispersive X-ray spectroscopy (EDX) unit. The acceleration voltage used was 25 kV.