This template'sinitial visibility currently defaults toautocollapse, meaning that if there is another collapsible item on the page (anavbox, sidebar, ortable with the collapsible attribute), it is hidden apart from its title bar; if not, it is fully visible.
To change this template's initial visibility, the|state=parameter may be used:
{{Petromyzontiformes|state=collapsed}} will show the template collapsed, i.e. hidden apart from its title bar.{{Petromyzontiformes|state=expanded}} will show the template expanded, i.e. fully visible.