Phylogenetic reconstruction of metazoan α-CAs relationships. The phylogeny was reconstructed using PhyML and Bayesian inference methods, the topology presented is that resulting from the PhyML method (see Additional file 2: Figure S1 for the Bayesian topology). Node support values indicate aLRT values, and Bayesian posterior probabilities expressed as a percentage respectively. Only values above 50 are indicated. Sequence data was derived from 4 vertebrate species (Homo sapiens, Mus musculus, Bos taurus, Gallus gallus, Oncorhynchus mykiss and Xenopus tropicalis, in black); 1 cephalochordate (Branchiostoma floridae; in grey); 1 sea urchin (Strongylocentrotus purpuratus, in purple); 1 annelid (Capitella teleta, in green); 1 mollusc (Lottia gigantea, in blue); 1 coral (Acropora millepora, in red); 1 placozoan (Trichoplax adhaerens, in pink); 2 sponges (Amphimedon queenslandica and Astrosclera willeyana, in orange); 1 fungi (Colletotrichum orbiculare, in black); 2 chromalveolates (Emiliania huxleyi and Vaucheria litorea, in black); 1 chlorophyte (Chlamydomonas reinhardtii, in black); and 2 bacteria (Nostoc sp. and Neisseria gonorrhoeae, in black). The α-CAs involved in biocalcification are in bold/underlined. CARPs: Carbonic Anhydrase Related-Proteins.