Like the title asks, what was the role of the antesignani in the later Republic?
From what I have read, ante means before and signani refers to the standard so they fought "before ( in front of ) the standard" – so a role like the velites.
They were part of Marius' reforms.
They are referred to as "elite legionary light infantry".
According to Eadie ( PDF link ) , Caesar "introduced mixed units of equites and antesignani ( lite infantrymen ) , which were employed against Pompeius' cavalry".
Yet, I had not heard of them before reading of them this morning.
Could they be based upon the German example of foot running alongside the horsemen?
Eadie continues with, "As the Romans expanded into Gaul and Germany and encountered resistance from barbarian bowmen and cavalry, however, military requirements changed.
The initial Roman response ( creation of the antesignani ) was conditioned by their legionary experience."
This clearly indicates they are not just employing foreigners to fight in this capacity, but they are employing legionaries to fight in this capacity.