Thrakian scuta question

[Forty-One]

...the parmula would be a small, round shield, which some might call a buckler.

Except that Junkelmann and others are calling the rectangular shield carried by [what are usually identified as] Thraeces a parmula. I don´t know what his ancient source for that is [if any], other than that Thraeces are usually counted amongst the parmularii. In gladiatorial terminology, at least, a parmula appears to have been the traditional name for a small shield of any shape. There are gladiators shown with both round and rectangular small shields.