Is this a case of taxon exclusion?
Perhaps… and yet, given the present taxon list, the thorny devil and the flying dragon are more closely related to each other than to any other taxa in the large reptile tree (LRT, 1087 taxa, Fig. 7).
Figure 1. Moloch in vivo. At present this is the closest relative of the flying dragon, Draco volans, in the LRT. That suggests a few more intervening taxa could be added.
With taxon exclusion, sometimes things like this happen.
The large reptile tree (LRT, 1087 taxa) has just a few agamid iguanids in its taxon list. The addition of the Australian thorny devil, Moloch horridus (Gray 1841), and its nesting with the SE Asian gliding dragon, Draco volans, reminds us that other well-known agamid lizards, like bearded dragons, would probably nest between them.
Figure 2. Skull of Moloch horridus, from Digimorph.org, with bones colored here. Note the maxillary teeth visible through the orbit in DORSAL view. The maxillary teeth are medially oriented. Grayscale image from Digimorph.org and used with permission.
It’s also notable
that the thorny devil does not nest with the similar but more distantly related horned lizard (Phyrnosoma, Fig. 6) of Western North America.
Figure 3. Skeleton of Moloch from Digimorph.org with certain bones colorized here. Note the fewer finger and toe bones. Dermal spikes shown in gray.
Figure 4. Draco volans. Note the anterior maxillary fangs, and the antorbital fenestra between the lacrimal and prefrontal, traits shared with Chlamydosaurus (Fig 2). Not the wide prefrontals, as in Moloch.
Lyriocephalus is the last common ancestor
to Draco and Moloch in the LRT. We looked at the skull and skeleton of Lyriocephalus (Fig. 5) earlier here.
Figure 5. Lyriocephalus in vivo.
Curious if the ancestors of Moloch
experienced a loss of jungle habitat and so adapted to scrub and dessert niches, since sisters and ancestors are jungle iguanids.
Figure 6. Phyronosoma, the horned lizard of North America.
For that matter
desert-dwelling horned lizards are most closely related to jungle-dwelling chameleons, like Trioceros, in the LRT (Fig. 7). Did horned lizards experience a similar loss of jungle? If so, that probably happened before the advent of the odd hands and feet of extant chameleons.
Figure 7. Subset of the LRT focusing on the Iguania. Gray box are extinct taxa.
The clade Iguania
(Fig. 7) goes back to the Early Permian with the MNC TA1045 specimen wrongly attributed to Ascendonanus, which we looked at earlier here and here.
Gray JE 1841. Description of some new species and four new genera of reptiles from Western Australia, discovered by John Gould, Esq.: Ann. Mag. Nat. Hist. (1) 7: 86-91.