Another for the genus confusion bank, Austrogomphus prasinus is also known as Austrogomphus (Pleiogomphus) prasinus. I believe that Pleiogomphus is regarded as a subgenus of Austrogomphus.
This is another one where the male of the species has forked anal appendages, like Austrogomphus divaricatus (Fork Hunter). Unlike Austrogomphus divaricatus, whose appendages are black, though, those of Austrogomphus prasinus are white. The small fork can be seen on some of these images.
Without the forked appendages, this species is almost identical to Austrogomphus amphiclitus (Pale Hunter).