Moving legs: A workflow on how to generate a flexible endopod of the 518 million‐year‐old Chengjiang arthropod Ercaicunia multinodosa using 3D‐kinematics (Cambrian, China)

• Published in: Microscopy research and technique 2021-04, Vol.84 (4), p.695-704
• Main Authors: Schmidt, Michel, Liu, Yu, Zhai, Dayou, Hou, Xianguang, Melzer, Roland R.
• Format: Article
• Language: English
• Subjects: 3D‐rendering; Amira; Animation; Appendages; Arthropods; Biota; Cambrian; Fossils; Functional morphology; kinematic research; Kinematics; Locomotion; Mobility; Morphology; Scientific Rotoscoping; srjoints; Workflow; X_ROMM tools
• ISSN: 1059-910X; 1097-0029
• DOI: 10.1002/jemt.23628

Understanding the functional morphology and mobility of appendages of fossil animals is important for exploring ecological traits such as feeding and locomotion. Previous work on fossils from the 518 million‐year‐old Chengjiang biota of China was based mainly on two‐dimensional information captured from the surface of the specimens. Only recently, μCT techniques started to reveal almost the entire, though flattened and compressed, three‐dimensionally preserved morphologies of the arthropods from Chengjiang. This allows more accurate work on reconstructing the possible movement of certain structures such as the appendages. Here, we present a workflow on how to reconstruct the mobility of a limb of the early Chengjiang arthropod Ercaicunia multinodosa from the famous Chinese fossil site. Based on μCT scans of the fossil, we rendered surface models of the 13th–15th right endopods using the 3D visualization and 3D‐rendering software Amira. The 3D objects then were postprocessed (Collapse Hierarchy, Unify Normals) in SAP 3D Visual Enterprise Author before being imported into the 3D animation program Autodesk Maya 2020. Using the add‐on tool X_ROMM in Maya, we illustrate step‐by‐step on how to make the articles of the limbs swing‐in toward each other. Eventually, we propose several possible limb movements of E. multinodosa, which helps to understand how this early arthropod could have moved its endopods. Based on surface reconstructions performed with Amira, we show a step‐by‐step workflow on how to generate a flexible endopod with movable articles using Autodesk Maya 2020 and discuss challenges for Chengjiang arthropod kinematics and mobility research.