Ventral Morphology and Ecological Implications of Cindarella eucalla (Artiopoda, Xandarellida) from Chengjiang Biota, China

Artiopoda, an early arthropod group, displays post-antennal appendages resembling trilobite limbs, but relationships with other ealy arthropods remain enigmatic. Limited studies and morphological details hinder the understanding of internal relationships within Artiopoda. Recently, exceptionally well preserved arthropod fossils from the Chengjiang Biota were studied using X-ray computed tomography, revealing detailed morphologies. In this study, Cindarella eucalla , a xandarellid from the Chengjiang Biota, was re-investigated using X-ray computed tomography and fluorescent microscopy to reconstruct its morphology and understand its phylogeny and ecology. This study successfully reconstructed a three-dimensional model of Cindarella eucalla , revealing features, such as spindle-shaped trunk tergites with the anterior six covered by the head shield and axial spines extending from the last four, natant hypostome, four post-antennal cephalic appendage pairs, dorsoventral mismatch existed between trunk tergites and limb pairs. This research suggests that Cindarella eucalla could escape in a very short time when it encounters an enemy, and it probably lived in muddy environments with ample light. Phylogenetic analysis indicates that Xandarellids may have close relationship with concililiterga or a clade composed of Nektaspida + (Conciliterga + ( Phytophilaspis pergamena + Trilobita)).