A Chiloscyllium punctatum (bamboo shark), phosphotungstic acid (PTA) stained microCT section with spiracular organ within a diverticulum close to the oral opening of the spiracular canal. B Chiloscyllium punctatum, adjacent section to A, showing orbital artery and its branch in apposition to spiracular organ. C Amia calva (bowfin), PTA stained microCT section, with pseudobranch ventrally and spiracular organ dorsally within the spiracular canal. Abbreviations: so, spiracular organ; oa, orbital artery; oa, l, lateral branch of orbital artery; ps, pseudobranch; s, spiracular canal. Scale bars: A=5mm, C=1mm.