a,b, Morphometric scans of the whole skeleton (a) and cranial bones (b) of the MHS holotype using micro-computed tomography. c, Gene structure (top), alignment of nucleotide and amino acid sequences (middle) and sequencing read depth (bottom; the numbers along the x-axis represent the position of the base at the scaffold) for the bglap gene. The premature termination (coloured red) of bglap is due to a single nucleotide insertion (coloured orange). The complete amino acid alignments of bglap are shown in Supplementary Fig. 23. d–f, Phenotypic differences in skeletal development between control-MO-injected zebrafish embryos (d) and embryos injected with bglap-e1i1-MO (e) and bglap-ATG-MO (f) at 5 days post-fertilization. In vivo visualization of the skeleton was achieved by adding a fluorescent dye (calcein) to the water housing the fish. Dyes that bind to calcified matrices can be used to label the entire skeleton. 5ba, fifth branchial arch; e, ethmoid plate; ec, ectopterygoid; m, Meckel’s cartilage; op, opercular bone; pq, palatoquadrate. Scale bars: 200 μm. g, Quantification of the relative fluorescence intensity (RFI) of the head skeleton bone mass. Columns heights and bars represent means ± s.e.m. (unpaired Student’s t-test, n = 10), ***P < 0.0001.