English: The tree, simplified from the strict consensus tree produced by our phylogenetic analysis, is time-scaled using the ‘minimal branch length’ method with a minimum branch length of 1 Myr (see Supplementary Fig. 5 for complete result and node support values). The thick lines indicate the temporal range of fossil taxa. An elongated fibula (in red) is developed in non-ornithothoracine Aves, and the most basal enantiornithines Protopteryx and Pengornithidae; a reduced fibula is convergently evolved in the Ornithuromorpha and derived enantiornithines. Cruralispennia preserves a plough-shaped pygostyle (in pink), which has long been considered unique to Ornithuromorpha (the pink branches). The apparent absence of tail fanning in Cruralispennia indicates that the plough-shaped pygostyle and tail fanning is evolutionarily decoupled in this lineage.