behaviour rather than a result of passive transportation and accumulation. A study on the phylogenetic relationships of the species and subspecies assigned to the phacopid genus Austerops is published by Oudot et al. (2019). A study on the morphological changes in the ontogeny of the Ordovician phacopid trilobite Calyptaulax strasburgensis is published by Jacobs & Carlucci (2019). A well-preserved body cluster of 18 specimens of Arctinurus boltoni is described from the Silurian Rochester Shale (New York, United States) by Bicknell, Paterson & Hopkins (2019). A study on development and evolution of the cephalon and the pygidium in phacopid trilobites is published by Oudot et al. (2019). A study on the internal structures of eyes of trilobites belonging to the genera Asaphus and Archegonus is published by Scholtz, Staude & Dunlop (2019); the study is subsequently criticized by Schoenemann & Clarkson (2021). A study on the variability of trilobite moulting behaviour is published by Drage (2019). New taxa Other arthropods Research A study on the morphology of appendages of the euarthropod Ercaicunia multinodosa from the Early Cambrian Chengjiang biota (China) is published by Zhai et al. (2019). Description of the appendicular morphology of Sinoburius lunaris is published by Chen et al. (2019). Description of a new specimen of Emeraldella brutoni from the Cambrian Wheeler Formation (Drum Mountains, Utah, United States), providing new information on the appendicular anatomy of this species, is published by Lerosey-Aubril & Ortega-Hernández (2019). Description of new bradoriid fossils from the Chengjiang biota, revealing hitherto unknown morphological differences in limb anatomy between bradoriid species, is published by Zhai et al. (2019), who evaluate the implications of this finding for the knowledge of the phylogenetic relationships of bradoriids. A study on the appendage structure of Naraoia spinosa at both juvenile and adult stages is published by Zhai et al. (2019). Description of exceptionally preserved soft tissues from mature individuals of Peronopsis and Ptychagnostus from the Cambrian Burgess Shale (British Columbia, Canada), and a study on their implications for inferring the phylogenetic placement of agnostinids within Arthropoda, is published by Moysiuk & Caron (2019). Completely enrolled, phosphatized specimens of Tsunyidiscus yanjiazhaiensis are described from Cambrian Stage 3 of South China by Dai et al. (2019). The ontogenetic series of Pagetia vinusta is documented from the Cambrian (Wuliuan) Kaili Formation (Guizhou, China) by Cui et al. (2019). A study reevaluating crystals of a copper sulfide mineral found in association with specimens