Illustrations of Sassanid Persian Clibanarii

[Renatus]

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.

A.D.H. Bivar in his paper "Cavalry Equipment and tactics on the Euphrates Frontier" and Professor Richard Frye in his book" The Heritage of Persia" both suggest that the Latin term clibanarius could be a loanword from Middle Persian suggested originally by Swedish Semitic etymologist Professor Frithiof Rundgren of Uppsala University Sweden

I cannot speak to Prof. Frye's book, other than that it is cited by Bivar in the footnote in which he summarises Prof. Rundgren's argument. I have to say that Bivar does not seem to express much enthusiasm for it. Rundgren's hypothesis is dismissed by the Russian scholar Valery Nikonorov, in the excellent paper cited by Urselius, on the grounds that it is too complicated and is purely hypothetical, suffering as it does from the major drawback that there is no Persian text that supports the proposed etymology. A much simpler explanation is that it derives from the Latin clivanus meaning 'cuirass'.

I think the Historiae Augustae Scriptores, Alexander Severus 56.6 mentions a victory over the Persians that his troops killed 10,000 of their mailed horsemen who the Persians call Clibanarius

The SHA is a work of the 4th or even 5th century and is highly unreliable. It cites documents that are generally regarded as forgeries and Alexander Severus' speech to the Senate, in which he makes this claim, is almost certainly one of them. It cannot be regarded as reflecting the language contemporary with the events it describes. Rather, it reflects the terminology and beliefs of the time when it was written. Nikonorov dismisses it as of no value in this discussion.

I also thought that Palmyran mailed cavalry were called clibanarii. mile:

Not as far as I am aware