Gaius Lucilius (Wikipedia, handle with care), c.160–103/2 BC, is considered the earliest Roman satirist. (Other sites give his dates a c.180–102.) Only fragments of his work remain. He was a Roman citizen of the equestrian class and belonged to the circle of Scipio Aemilianus. Horace was influenced by him, and Lucilius appears in several of the latter's satires:
BkISatIV:1-25 Horace praises and also criticises him.
BkISatIV:26-62 An example of a great Satirist.
BkISatX:1-30 Horace’s criticism of his style.
BkISatX:50-71 Lucilius’ own criticism of others.
BkIISatI:1-23 He wrote about Scipio Africanus.
BkIISatI:24-46 Horace considers Lucilius a better man than himself.
BkIISatI:47-86 Lucilius’ satires were tolerated.
Jacques Perret in his Horace points out similarities, such as being part of a circle around the patron: Aemilianus/Maecenas, the independence of being an equestrian, chroniclers of little groups, etc. He writes, "[Horace found], in Lucilius, the assurance that one could build a literary work around one's own person. Perhaps no Greek author would have have encouraged him in that direction."
Smith's Dictionary of Greek and Roman Biography and Mythology has almost three full columns on Lucilius and blames Jerome for the confusion about the dates.
Perret writes that Pliny the Elder called Lucilius the founder of literary criticism. The chapter "Rome's first 'satirists: themes and genre in Ennius and Lucilus" (Frances Muecke) in The Cambridge Companion to Roman Satire (Cambridge Companions to Literature), groups him with Ennius though. Relevant partial previews can be be found in this Google Book of the above: