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Alright, what can we get from this one? The median suture on the head extends upwards from the anterior region so it's definitely Spirobolida. From there ALA lists 4 families in Australia. Pachybolidae contains the single species Xenobolus carnifex which is quite different and seems to be an introduced species in Australia from what I have read (although I have seen a similar native in Iron Range...), so it's not that family. Spirobolellidae contains two genera, Spirobolellus and Walesbolus, but of which are found further south and seem to be a fair bit smaller, so once more that is out.

So our two families up this way are Rhinocricidae and Trigoniulidae. I've never really worked out a good way of distinguishing millipede families because most of the features used are based on male genitalia. The easiest feature I have been able to find to distinguish Rhinocricidae and Trigoniulidae is the shape of the collum (the broad first segment of the body, behind the head). In all rhinocricids it is very broadly rounded on the sides, and not narrow like mine. In the trigoniulids it's more variable and sometimes is broad, but if it's skinny like this then you know for sure it's a trigoniulid.

In Trigoniulidae we have 6 genera, 4 of which are monotypic. Ainigmabolus chisholmi is from NSW, Austrostrophus stictopygus and Speleostrophus nesiotes are both from WA, and Leptogoniulus sorornus is introduced and looks like this:

Trigoniulus and Zygostrophus both have more species and I am not sure how easily distinguished they are. Unfortunately I do not have access to the document that splits them (and describes many species), Chamberlin's (1920) The Myriapoda of the Australian Region. Alas! This paper has a good key to some of the species though, so we'll see what we can rule out. T. insculptus and Z. digitulus have the collum rugose so they are out. T. montium has the sides of the collum wrinkled, and it is a dull greyish colour (and known from NSW only). T. hemityphlus is darker and has ocelli in 3-4 rows only. And T. hebes is reddish with the head, collum, and telson dark greyish (and once again only from NSW). That unfortunately is where the key stops though, alas. And there is also where we must stop, because there are a number of species that I just cannot access any information on unfortunately. If anyone can tell me the difference between the two genera that would be very helpful, but for now we are stuck at family. This paper however seems to indicate that Zygostrophus is the more dominant genus in Australia, so just on likelihood that is probably what I have here.

6mm
variably colourful, [greens or browns on white]
non tuberculate, largish punctures partly concealed
alternate interstices raised, particularly 3rd near base
5-7mm
on twigs of fallen tree crown, Syzygium crebrinerve

TNP Joalah