Early Cretaceous stem chameleon/horned lizard

Unnamed stem chameleon (Daza et al. 2016; Early Cretaceous, 1.2cm in length; JZC Bu154; Fig. 1) is a tiny neonate preserved in amber. It also nests basal to horned lizards like Phrynosoma, in the large reptile tree (LRT, 1089 taxa). Note the long, straight hyoid forming the base of the shooting tongue. The split fingers and toes of extant chameleons had not yet developed in this taxon. Found in amber, this newborn lived in a coniferous forest.

Figure 1. The Early Cretaceous stem chameleon/horned lizard found amber. Snout to vent length is less than 11 mm. Much smaller than a human thumbnail.

Figure 1. The Early Cretaceous stem chameleon/horned lizard found amber. Snout to vent length is less than 11 mm. Much smaller than a human thumbnail. Insitu fossil from Daza et al. 2016,  colorized and reconstructed here. At a standard 72 dpi screen resolution, this specimen is shown 10x actual size.

This specimen further cements
the interrelationship of arboreal chameleons and their terrestrial sisters, the horned lizard we looked at earlier with Trioceros and Phyrnosoma in blue of this cladogram (Fig. 2) subset of the LRT.

Figure 3. Subset of the LRT focusing on the neonate stem chameleon/horned lizard.

Figure 2. Subset of the LRT focusing on the neonate stem chameleon/horned lizard.

Figure 6. Phyronosoma, the horned lizard of North America.

Figure 3. Phyronosoma, the horned lizard of North America.

Figure 2. Trioceros jacksonii overall. Size is 12 inches (30 cm) from tip to tip.

Figure 4. Trioceros jacksonii overall. Size is 12 inches (30 cm) from tip to tip.

References
Daza JD et al. 2016. Mid-Cretaceous amber fossils illuminate the past diversity of tropical lizards. Sci. Adv. 2016; 2 : e1501080 4 March 2016

DGS finds sutures in Trioceros (Jackson’s chameleon) skull

I wanted to add a chameleon to the large reptile tree because I had only three taxa in the Iguania, Draco, Phrynosoma and Iguana. The problem is, the skull of Trioceros jacksonii, (Jackson’s chameleon, Fig. 1) has very indistinct sutures. So I used DGS.

Figure 1. The chameleon Trioceros jacksonii colored using DGS. The sutures are difficult to see in the original skull, much easier in the colorized tracing.

Figure 1. The chameleon Trioceros jacksonii colored using DGS. The sutures are difficult to see in the original skull, much easier in the colorized tracing.

Using the above data, gathered after determining skull sutures with DGS, Trioceros nested with Phyrnosoma (the horned lizard) which shares the following traits: 1) tiny premaxillary teeth; 2) vertical quadrate; 3) squared off (hyper-exaggerated in this case) rostral profile; and 4) several other traits. And, nicely, that’s exactly where others nest it.

I don’t know chameleon skulls so well (this is my first exposure). The dentary appears to extend a bit too far behind the coronoid, but then, maybe that’s what chameleons do. Comparisons to other species seem to bear this out.

Figure 2. Trioceros jacksonii overall. Size is 12 inches (30 cm) from tip to tip.

Figure 2. Trioceros jacksonii overall. Size is 12 inches (30 cm) from tip to tip.

Jackson’s chameleon gives birth to live offspring. Eight to thirty are born after a six-month gestation. Sexual maturity is at 5 months of age. Adutl size is 12 in. (30cm). The diet is insects caught by a hyper-extensible tongue. The tail is prehensile. Fingers 1-3 oppose fingers 4 and 5. Toes 1 and 2 oppose toes 3-5, as in other chameleons.

References
Boulenger GA 1896 Description of a new chameleon from Uganda. Annual Natural History 6(17):376.

wiki/Trioceros