I like 2019 -A- 15. I have seen these francolins in Hawaii. The proposal mentions Ortygornis for erckolii? Wolters puts only pomdicerianus there.
“Pternistis erckelii is similar to the rest of the spurfowls, but has a distinct jaw line which is only partly visible on the jaws of a few other spurfowls.”
“There are more stripes on the side of the face of Pternistis erckelii than in other spurfowls, such as having a distinct jaw stripe and a thin stripe above the orbit which is more bold and typical of Scleroptila spp. and female P. coqui. The jaw stripe is only faintly visible on some other spurfowls. Ostensibly, while this seems to be a logical course of evolutionary events, for instance that P. erckelii could link the spurfowls and Scleroptila spp.”
“The prominent jaw stripe of P. erckelii (and to a lesser extent by other spurfowls) is also evident in Coturnix coturnix, N. meleagris and V. acryllium chicks.”
“P. icterorynchus, P. nobilis and P. erckelii, (chicks) generally have a reddish appearance, but their patterns (structurally) remain like the rest.”
The phylogeny of francolins (Francolinus, Dendroperdix, Peliperdix and Scleroptila) and spurfowls (Pternistis) based on chick plumage (2018) Perhaps P. erckolii needs its own genus?
Wolters in Die Vogelarten der Erde puts P. erckelii in an unnamed subgenus along with P. ochropectus castaneicollis, jacksoni, nobilis, camerunensis, and swerstrai. Wolters also put a few species of P. into Chaetopus Swaison 1837.