Was artillery used in the field?

[Eleatic Guest]

My question is this: did the Romans ever use artillery in the open battlefield i.e. not in a siege environment? I'm mainly concerned with the period from the Early Republic (Punic Wars) to the Early Empire up till the 2nd century AD. Most of the sources that I've read suggest that the ballista, scorpio and other similar catapults were only used in sieges, never in the open battlefield.

I am having the same question:

- Are there any further sources suggesting the use of field artillery in the above period? I find the relative lack rather curious, since the first mention of artillery as a means of supporting troops in the field comes as early as Alexander's Thracian campaign in the 330s BC (Macedonian artillery supported the crossing of a river). So what took it so long for the Romans?

- When was mobile artillery (cart-based) first used by the Romans?

Regards