Axonophoran colonies are scandent and ancestrally biserial, with both stipes being connected by their dorsal sides. The nema (identical to the virgula) of axonophorans served as a central rod along which the stipes grew. In axonophorans with a dicalycal theca, the two thecal series are separated by the median septum, a wall shared by the dorsal sides of both stipes. In relief material, the median septum can be distinguished by a line separating the thecal series.[1]
In some taxa (e.g. Urbanekograptus, early Climacograptidae, and Dicranograptidae), crossbars created as part of the median septum connect the nema to the intrathecal septum, a wall shared by neighboring thecae of the same stipe. In taxa with these crossbars, the intrathecal septum is folded and the median septum is undulating or zigzagged. However, other taxa can have a straight median septum or lack one entirely, in which case the thecae usually grow alternately, forming a unistipular, biserial colony.[1]
Like in other graptolites, the sicula is composed of the prosicula with a helical line and the metasicula formed by the secretion of fuselli. The prosicula is composed of conus and cauda, like in other graptolites, and the nema is deposited in fusellar increments as a spine emerging from the cauda.[1]
The thecae of axonophorans are quite diverse. The ventral (outer) thecal wall can be straight or have a geniculum (a sharp bend in the thecal wall). The geniculum, if present, can bear a flange or collar. The thecal aperture can be oriented inwards, horizontally, or outwards and can bear a wide range of apertural elaborations like lateral lobes, paired apertural spines, hoods, or lappets.[1]
