PHYLOGENY, DISPARITY AND MORPHOSPACE OF ANOMALOCARIDS: FOSSIL EVIDENCE FROM CHINA

The anomalocarids during the Cambrian explosion were the earliest apex predators in the Phanerozoic marine food webs. The peculiar anomalocarid body plan showed key transitional features from basal panarthropods to euarthropods and exhibited high adaptation to predation, providing crucial evidence for the origin and early evolution of arthropods. Continuous fossil discoveries in recent years have revealed an unexpected global diversity of anomalocarids. Among these, the Burgess Shale-type Lagerstätten in China have yielded diverse exceptionally preserved anomalocarids from the Cambrian Stage 3 to Drumian, which open a new window to reveal the tempo and mode in the evolution of anomalocarids.

On the basis of these new materials, an updated morphological dataset of anomalocarids with new characters is built. An anomalocarid phylogeny of significantly improved resolution is reconstructed by using various models in maximum parsimony and Bayesian inference. The monophyly and inner relationships of main anomalocarid families are well resolved. The morphological disparity and phylomorphospace of anomalocarids between groups and through time are investigated based on a data subset coding the anomalocarid raptorial frontal appendages. Multiple disparity measures are used to compare the various aspects in morphospace occupation of anomalocarids. Little overlapping in evolutionary trajectories and occupation of anomalocarid families in the morphospace suggests that their disparities are mainly controlled by phylogenetic factors, supporting independent origins of suspension feeding in anomalocarids. Temporal changes in anomalocarid disparity and morphospace witnessed the rise and fall of main anomalocarid clades between the Cambrian Series 2 and Miaolingian. This macroevolutionary shift in anomalocarids, which were high-level predators in the Cambrian ecosystems, provide new evidence for a possible major extinction event in the Cambrian Series 2 to Miaolingian transition.