Additional elements were added in different orientations by extruding existing elements, thereby modelling other parts of the fossil. The vertices and edges of this object were then translated, rotated and scaled to fit the outline of the reference images in dorsal, ventral and frontal views.
First, the cube was subdivided to increase the number of elements. For each model, a primitive cube was used as a base object. Two-dimensional reconstructions of the cinctans in multiple orientations were taken from the published literature, scaled to life size and used as reference images to guide box modelling in Blender v. Methodsģ-D digital models of the cinctans Graciacystis ambigua, Gyrocystis testudiformis, Lignanicystis barriosensis, Protocinctus mansillaensis, Trochocystites bohemicus and Undatacinctus quadricornuta were constructed. This study provides evidence of a previously unknown evolutionary trade-off between feeding and stability in Cambrian cinctan echinoderms. However, unlike the flattened forms, cinctans with high-relief bodies were able to passively direct flow towards the mouth and associated food grooves, indicating that they were capable of more efficient feeding on particles suspended in the water. The results demonstrate that cinctans with strongly flattened bodies produced much less drag than species characterized by dorsal protuberances or swellings, suggesting the former were more stable on the seafloor. Three-dimensional models of six species from across cinctan phylogeny were used in computer simulations of water flow. Here, we used computational fluid dynamics to analyse the functional performance of cinctans without assuming an extant comparative model. Cinctans, an enigmatic group of Cambrian echinoderms, exemplify this problem: their asymmetrical body plan differentiates them from all living species. Reconstructing the function and behaviour of extinct groups of echinoderms is problematic because there are no modern analogues for their aberrant body plans.
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