However, there are numerous aspects of the Roman army that were not carried into the Ptolemaic and Seleucid ones. For example, the differentiation of the Hastati, Principes and Triarii, or the integration of light-armed troops into the infantry structure. Hence, because of this, there was no Hellenistic equivalent to the Cohort. Instead, there was a system of larger units that had no relation to Roman organization. In terms of equipment, most of these so-called 'Romanized' troops did not abandon their traditional spear for a sword, which the Hastati and Principles abandoned between the 3rd and 2nd Century BC. Also the Romans used the pila, while Greek troops tended to use local variations of Javelins. Also similarity of equipment in regards to helmets and chain-mail can be explained by Celtic influence experienced by both the Greeks and Romans at a similar time. In this sense, we can only assume that the Hellenistic kingdoms did reform and re-organize their troops in some regards along Roman lines, but these appear to be superficial at best and quite possibly the result of convergent evolution, with both cultures influencing each other.