Adult morphology of the zebrafish caudal fin skeleton. A. A 22 mm SL zebrafish, showing the differences between the preural and ural region. B. Diagram of the terminal compound centrum of a 31.92 mm SL zebrafish illustrating its preural-ural boundary. C-H. series of cleared and stained zebrafish showing the main changes of the compound terminal vertebra. Terminology: CC, compound centrum; cU3–4, ural chordacentra 3 and 4; E, epural; H1–5, hypurals 1 to 5; haPU1, haemal arch of the preural centrum 1; hy, hypurapophysis; naCC, neural arch of the compound centrum; PH, parhypural; PL, pleurostyle; PU2, preural centrum 2; Un, uroneural

Mineralization of the compound terminal vertebra. A–I. Zebrafish larvae incubated in Alizarin red S and visualized through confocal microscopy. J–L. 3D reconstructions of cleared and stained individuals visualized through confocal microscopy. Red arrowhead points to the lateral middle ridge or crest. Terminology: cU1 + 2, ural chordacentrum 1 + 2; cU1–3, ural chordacentra 1 to 3; H1–5, hypurals 1 to 5; haPU1, haemal arch of the preural centrum 1; naU1-U2, neural arch of the ural centra 1 or 2; PH, parhypural; PL, pleurostyle. Scale bar: 100 μm

Patterning of the autocentrum. Confocal images of the osteoblast transgenic reporter sp7:nlsGFP, counterstained with the bone marker alizarin red S, were taken at different stages of zebrafish development to show the conformation of the compound centrum. Terminology: aut, autocentrum; cU1 + 2, ural chordacentrum 1 + 2; H1–5, hypurals 1 to 5; haPU1, haemal arch of the preural centrum 1; naPU1-U1-U2, neural arch of the preural centrum 1 or ural centra 1 or 2; PL, pleurostyle. Scale bar: 100 μm