ELKHORN OR STAGHORN?: P. hillii, P. bifurcatum, P. veitchii. In Australia these three species are commonly called "elkhorn" to distinguish them from P. superbum, also native to Australia, which is called "staghorn". P. hillii and P. veitchii are also specifically called "northern" and "desert" elkhorns, respectively. That seems to distinguish them from P. bifurcatum, which is more common and known as "southern" elkhorn.
Meanwhile in the US, the terms elkhorn and staghorn are often used interchangeably. In addition, the large platyceriums (P. superbum, P. grande, P. wandae and P. holttumii) are also sometimes called "moosehorn"
Perhaps it would be better just to call them all "staghorn" in order to avoid confusions and ambiguities. They could then be distinguished by their species epithet or other unique terms.
P.S. The term "elkhorn" also commonly refers to a terrestrial fern called Microsorum punctatum aka Polypodium 'Grandiceps' or "Climbing Bird's Nest Fern" (see the last picture).