Euzonoi ?

[Menander of India]

There is this unit which appears for the 1st time in Xenophon(IIRC) and he's probably been referring to light infantry in general(psiloi). However, Polybian mentions them as a unit of hybrid light infatry separate to those of peltasts and other psiloi. For example they appear in the 3rd battle of Mantineia , Selasia etc.Their armament is described as too narrow thyraioi for covering the whole body, plus spears which were not as long as pikes.He also adds that although they could skirmish successfully in a frontal fight would have been in a disadvantage. Could this be a separate unit or is just a version of Thyreophoroi? What do you think ?