As Paullus wrote, I was referring to those handful of figurines from Selecia in reference to the oriental Tarentines, as well as the hypothesis made by Bar-Kochva and others that the Tarentines mentioned in later Seleucid sources were almost certainly orientals trained in the Tarentine mode of fighting.

I, too, have heard the mention of Parthian phalangites, but I've never seen any actual evidence turn up to support that claim. As with so many things on the internet, I think it could just be speculation run amok and transformed into fact.