I am sure you are all aware that the species D.bilineata has had a significant revision by J. Melville et al; in a paper published in 2019 by Museums Victoria, the group has seen significant reclassification resulting in splits into several new species and elevation and removal of previous subspecies status. This means that D. bilineata has now been confined as a species to a greatly reduced range that takes in the very top end of the NT including the Northern half of Arnhem Land. At this point in time it is generally considered that the only Diporiphora species that have a range that includes Central Arnhem Land are D.bilineata and D.magna There is also D.sobria that has a range that skirts the southern edge of Arnhem Land. All 3 species are found west of the Arnhem land boundary. The paper also rolled D.arnhemica, (which was considered part of the D.bennetti complex (although most authors had it as a stand alone species) into the newly established full species of D.sobria. I am aware of some discussion that there may need to be further revision of this group and even the Melville J. et al paper itself suggests the potential for further work with their treatment of D. arnhemica being synonomised into D.sobria.
In my opinion none of the pictures show D.sobria, which is a much more robust species and has obviously different markings. I agree with Bluetongue in that picture 3 is most likely a very dull D.magna. I say dull because the ones I have seen and kept are generally much more vibrant with obvious yellow/lemon flanks and a very dark if not black patch just above and behind their front legs. This colouring is much more obvious on males but still apparent on females. They can also and tend to, have a pinkish hue to the tail base which is quite common on a number of the Diporiphora species.
The first two pictures are D.bilineata based on what we now regard as D.bilineata. My opinion is based on tail and body markings, slender body size, apparent lack of a gular fold and known distribution for the species.
The Diporiphora genus of dragons can in some species show tremendous variation even in a geographically restricted single species. They are sometimes incredibly hard to actually ID with real accuracy particularly without knowing the region where the animal is found. Its all part of the fun and more importantly the process of learning about the species, the genus and the family of dragons generally.
Hope my input and comments helps.
