Fig. 1

A Molecular phylogenetic reconstruction of 3FTx showing extensive duplication preceding organismal diversification combined with lineage-specific duplication events. Grey shaded sequences represent the dimeric forms that have evolved convergently in Boiga and Spilotes. Additional Files contain sequence alignment used for constructing phylogenetic tree (Additional file 1), tree output file (Additional file 2), and zoomable high-resolution tree image (Additional file 3). RFS = rear-fanged snake. B Sequence alignment of representative basal-type 3FTx. Ancestral cysteines are shaded in black. Newly derived dimeric inter-chain cysteines shaded in colour. Propeptide domain shaded in grey. Signal peptide amino acids shown in lowercase