In 2019 the crocodiles of southern New Guinea were formally separated from Crocodylus novaeguineae and named Crocodylus halli, honouring Philip Hall, who had documented the differences in the 1980s but died before publishing a formal description.
The case rested on measurable differences in skull shape and proportions, adult size, and reproductive timing: southern animals nest in the dry season while northern ones nest in the wet. Material for the description came largely from museum collections and captive animals of known origin, supplemented by molecular comparison. It is an unusual thing to happen to a large, conspicuous vertebrate, and it illustrates how species boundaries in widespread reptiles can go unexamined.
Because the species is new, its conservation status has not been separately assessed by the IUCN in the way its northern relative has, and population estimates specific to it are thin. Whether all southern New Guinea populations belong to C. halli has not been fully worked out.