Kyrgyzsaurus restored via phylogenetic bracketing

Earlier we looked at a new Late Triassic reptile, Kyrgyzsaurus. Alifanov and Kurochkin (2011) considered it a basal drepanosaur, perhaps by misidentifying several bones and by not including any taxa other than drepanosaurs in their analysis.

Kyrgyzsaurus comes from the same insect-laced deposits that yielded Sharovipteryx and Longisquama in the 1960s. Phylogenetic analysis nested Kyrgyzsaurus between the basal fenestrasaur, Cosesaurus and Sharovipteryx.

Kyrgyzsaurus is known only from its anterior parts, sans the forelimbs. If we wish to guess what it looked like restored (Fig.1), we have to rely on phylogenetic bracketing to create a best guess model based on closest known kin.

Figure 3. The origin of pterosaurs now includes Kyrgyzsaurus, nesting between Cosesaurus and Sharovipteryx.

Figure 3. The origin of pterosaurs now includes Kyrgyzsaurus, nesting between Cosesaurus and Sharovipteryx. Click to enlarge. 

Larger than its cousins
Kyrgyzsaurus had robust, parallelogram-shaped cervicals that indicate this reptile typically raised its head above its shoulders, like a theropod dinosaur and very much like Cosesaurus. The shoulder girdle was relatively larger, suggesting the presence of large forelimbs. A quadrant-shaped coracoid suggests a flapping behavior, as in pterosaurs and birds. Phylogenetic bracketing gives Kyrgyzsaurus a long, attenuated tail, compressed metacarpals, fingers that were longer laterally, but with manual digit 5 a vestige. A pteroid and preaxial carpal would have been present. The pelvis would have included an anteriorly elongated ilium and fused pubis/ischium with the addition of a prepubis. The tibia and femur were long. Whether the tibia was longer than the femur is up for grabs. The fifth toe might have hyper flexed. Soft tissue would include a dorsal frill, a hairy tail, forelimbs with trailing tissue, and hind limbs with uropatagia.

Like Cosesaurus, only bigger
Among the fenestrasaurs, Kyrgyzsaurus is most like Cosesaurus (Fig. 1, Middle Triassic), but with a relatively shorter snout, smaller head, longer neck and more robust pectoral girdle. Soft tissue is extensive but poorly defined due to breakage of the substrate.

Kyrgyzsaurus represents yet one more radiation from the small generalized form that is Cosesaurus. As a cousin to Longisquama (Fig. 1) who knows how elaborate the dorsal decorations of the larger Kyrgyzsaurus really were.

Flapping, not flying
While pterosaurs were first making their way into Late Triassic skies, their cousins (Fig. 1) the nonvolant fenestrasaurs, were running around flapping and climbing trees to glide from one to another. Kyrgyzsaurus was larger than the others, but it is unknown yet whether that made it more terrestrial or not, depending on the proportions of the limbs and torso.

Alifanov VR and Kurochkin EN 2011. Kyrgyzsaurus bukhanchenkoi gen. et sp. nov., a new reptile from the triassic of southwestern Kyrgyzstan. Paleontological Journal 45(6): 639–647. doi:10.1134/S0031030111060025.


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