Illustrations of Sassanid Persian Clibanarii

[Urselius]

Would you interpret 'masked' as the defining feature separating cataphracti equites from their specific sub-group clibanarii?

No. Cataphracti/cataphracti equites and clibanarii are the same. Cataphracti and cataphracti equites are synonymous and are general terms for this type of cavalry, whether Roman or non-Roman. Clibanarii are specifically Roman.

If there was no functional difference between clibanarii and cataphracti then why did the Romans only apply the nomenclature clIbanarii to their own troops? Bearing in mind that some of their own units were named catafractarii (eg. Equites Cataphractarii Iuniores) and other units termed clibanarii had non-Roman ethnic names (eg. Equites Persae Clibanarii and Equites I Clibanarii Parthi). It seems to me that, if functional differences were not involved, the two terms were used indiscriminately by the Romans.