They are, in the way of metre, choriambics; and a choriambic is a quadrisyllable foot.
For the quadrisyllable ending to the pentameter, see at ii 10 Alcinoo (p 164).
But Alexandrides lengthens the word into a quadrisyllable, and calls it .
quadrisyllable, kwod-ri-sil′a-bl n. a word consisting of four syllables.
quadrisyllable endings are frequent in the metrically strict Claudian.
For Ovid's use of quadrisyllable endings for pentameters, see at ii 10 Alcinoo (p 164).
Doing this, they make the word a quadrisyllable; for less than this would fall short of the demands of the metre.