Evolutionary relationships within the Avalonian Ediacara biota: new insights from laser analysis

摘要

We report new high-resolution laser scanning of the type material for the earliest, complex Ediacaran genera Charnia, Bradgatia, Charniodiscus and Ivesheadia from Charnwood, UK, and compare these with Beothukis mistakensis gen. et sp. nov. and the recently described taxa Charnia wardi, Charnia antecedens and Fractofusus spp. from broadly coeval strata in Newfoundland. We use the laser and other techniques to map the similarities and differences in morphology between these Ediacaran rangeomorphs. Key features are suggested to include the number of growth axes, the number and placement of growth tips, the presence of radiating or subparallel axes for the first- and higher-order branches, the extent of displayed or undisplayed leaf-like ’rangeomorph' architecture, and the extent of furling of the margins of these leaf-like elements. These features are then used to propose suggested homologies between these taxa, leading to a preliminary phylogenetic hypothesis for the evolution of the Avalonian Ediacara biota.