Both the first two photos I believe are Diporiphora bilineata. But the third photo I don't know. All these were in the same locality in Central Arnhem Land, about 100 kms inland. Any opinions on these would be appreciated, thanks.
The top pic looks to be Diporiphora arnhemica. The shadow below the eardrum appears to be caused by a postauricular fold and it looks to have a weak gular fold. The middle pic seems to be a correct ID to me – no head folds and an enlarged dorsolateral row of scales.
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.
Thanks for that longirostris. Unfortunately I was not aware of the published revision. Personal circumstances took me out of reptile circles for the last few years and I have not kept up with all that has happened in the interim. I wiil admit, however, that this one was to be expected and I probably should have done some googling before responding to the query. The last time I spoke to Paul Doughty, which was a few years back now, he mentioned there was still a lot of work to be done on the northern species. At that time, as I recall, he was up to his eyes in frog and gecko taxonomy and the northern Diporiphora were just a “will get to it sometime in the future” task.
I will have a read of the paper and get back to you.
This is also D.bilineata. Quite strikingly marked for a female, which is unusual. The females in most Diporiphora species are quite bland if not dull with minimal or no patterning and or colouring. This is definitely a female as there are no obvious hemipene bulges on either side of the base of the tail. These are always very pronounced and quite apparent in males of a number of Diporiphora species but particularly species in the D.bilineata complex and D.australis.
@tropicbreeze. The additional photos confirm that the shadow I thought may be due to a fold behind the ear was simply due to the angle of the head. The pics of the other specimen confirmed this and also showed the presence of a weak scapula fold and no gular fold. So clearly it is in fact D. bilineata, so that was a good call by you. Thanks for that extra input.
@longirostris. What you said about patterning was quite interesting. My perception had been that juveniles and females tended to be more strongly patterned, while adult males tended to be less so, without including the reduction in basic patterning that can accompany breeding colours. However my experience with this genus is pretty limited. Funny how one can percieve certain things.
I have had a good read through the revision and found it very interesting and illuminating. It cleared up one thing that used to puzzle me, that being how D. bennettii could have different forms - relatively short and dumpy to longer and much more elongated. Lizard species do not normally vary in that manner.
The other thing was the degree of variation in pattern within a species. From very early on I have been aware of agamids’ ability to alter colour according to their circumstances and that the patterning can change in intensity from hatchling to adult. However I had never equated dragons as being like certain skink species, where memnbers of the one species can be heavily patterned to basically patternless. So I have learned something new.