The biodiversity of coral reefs is globally estimated to be represented by around 950.000 (±40%) multicellular species and only 10% of them have been described (Fisher et al. 2015). These numbers indicate the vast gap in our present knowledge of coral reef biodiversity and how much documentation work remains. Although the highest concentrations of coral reef species can be found in ‘the Coral Triangle’, located in the Central Indo-Pacific (Hoeksema 2007), new species richness records from just outside this area indicate that the boundaries of this diversity centre remain contested and the knowledge bank of reef coral distribution ranges continues to shift (Hoeksema 2015; Huang et al. 2015; Lane and Hoeksema 2016; Veron et al. 2015). Fixed Coral Triangle boundaries may matter in the context of reef conservation management policies (Christie et al. 2016; Venegas-Li et al. 2016), but if precise boundaries and a triangular shape are not recognisable for a centre of maximum marine diversity in a biogeographical setting, it might be more appropriate to refer to it as the Indo-Australian Archipelago or Indo-Malayan region (see review by Hoeksema 2007).