Cohort commander?

[D B Campbell]

For the early republic Dionysius for the year 487 BC briefly describes the career of Lucius Siccius being promoted to centurion then later to the commander of a cohort.

Rightly or wrongly, Dionysius seems to assume that there's a hierarchy of centurions, so that the centurio prior takes precedence over his manipular colleagues (cf. IX.10.2 for the primus pilus as "commander of the 60 centuries"). In this way, the centurio prior of the triarii could be said (by a first century writer) to be the commander of the cohort (though it is surely debateable whether anyone in the early-middle Republic would have thought in anything other than manipular terms).

btw The Lucius Siccius you refer to is usually known as Lucius Siccius Dentatus, and his speech, "quoted" by Dionysius, is usually thought to be Dionysius' own invention.