This Australian member of this genus appears to be only distantly related to the South-East Asian species.2 - Hugall et al. (2008). Phylogeny of Australasian agamid lizards based on nuclear and mitochondrial genes: implications for morphological evolution and biogeography. Biological Journal of the Linnean Society, 93(2):343-358. An old genus name, Istiurus, has been resurrected for the Australian species3 - Townsend et al. (2011). Phylogeny of iguanian lizards inferred from 29 nuclear loci, and a comparison of concatenated and species-tree approaches for an ancient, rapid radiation. Molecular Phylogenetics and Evolution, 61(2):363-380., but the validity of this name is doubtful. The name Intellagama4 - Wells & Wellington (1985). A classification of the Amphibia and Reptilia of Australia. Australian Journal of Herpetology, Supplementary Series, 1:1-61. is available and appears to be valid.

A 21 million-year-old fossil that is very similar to the Physignathus lesueurii has been found at Riversleigh, Queensland.5 - Covacevich et al. (1990). Miocene dragons from Riversleigh: new data on the history of the family Agamidae (Reptilia: Squamata) in Australia. Memoirs of the Queensland Museum, 29:339-360.