Pre-Marian marines

[M. Demetrius]

"... urging them to go barefoot instead) clearly shows that marines also used caligae, at least while operating on land.

Well, at the risk of splitting hairs, it shows that they wore SOME kind of leather shoes--though not necessarily caligae, but that they were not allowed extra money for hobnails. Our marine unit wears shoes like this, which are attested more or less in some statuary. Whether Marines wore them in history is presently unknown to us. Ours do not have hobnails.