Various traditional and digital morphological visualization techniques, shown in an exemplary fashion using cidaroid sea urchins (Echinoidea: Cidaroida). A Habitus of a museum specimen of Eucidaris metularia (NHM 1918.104.22.168-40), aboral view. B Historical drawing of the internal anatomy of Cidaris cidaris, a closely related species - modified after Stewart . C Volume rendering of the external anatomy of the specimen shown in A, based on a ~25 GB large μCT dataset with 13.91 μm isotropic resolution. D Virtual horizontal section of the μCT dataset at the level of Aristotle's lantern (see also Fig. 2). E Surface rendering of the external and internal anatomy of the specimen shown in A based on a ~100 MB large 3D MRI dataset with 81 μm isotropic resolution. F Virtual horizontal section of the MRI dataset at the level of Aristotle's lantern, digestive tract, and gonads. By clicking anywhere onto this figure, an interactive, partially labeled 3D model of the analyzed species will open (requires Adobe Acrobat Reader 8.0 or higher, see [10, 43, 44, 46] for detailed information regarding 3D modeling and labeling). The museum specimen of Eucidaris metularia was photographed using a digital camera with 7.2 megapixel resolution (Exilim: Casio Computer Co., Tokyo, Japan). 3D visualization was carried out using volume rendering in VG Studio Max 2.0 (C) and threshold-based as well as manual segmentation followed by surface rendering in Amira 5.2 (E).