Hierarchal tree analysis of crystallographic structures of RCvir deposited in the Protein Data Bank. Crystal structures are sorted according to the mean difference of their internal distances, as described by Wickstrand et al. (2015). The LCP SFX structures described here (PDB entry 7q7p, data collected at SACLA; PDB entry 7q7q, data collected at SwissFEL) form their own cluster, but have a mean internal distance-matrix difference on Cα atoms of 0.35 Å relative to all other RCvir structures. Although the space group (P21212) is the same as that found for earlier LCP crystal structures of RCvir, the unit cell has a significantly shorter c axis than that recovered in the low-temperature LCP crystal structures.