Exostinus lancensis model, WIP. Due to extremely fragmentary nature of fossil material, model is based on modern Xenosaurus.
As stated above, Exostinus lancensis belongs to the family Xenosauridae, which currently consists of a single extant genus. Modern Xenosaurus are native to Mexico and Central America, and are distinguished by knob-like scales, and a flattened head and body - this is an adaptation for living in cracks within cliff faces. The genus Exostinus actually includes a second species, E. serratus, which appears to be problematic. This is because a recent phylogenetic reanalysis of the family Xenosauridae recovered E. lancensis as sister to E. serratus and Xenosaurus, which would make the genus paraphyletic (Bhullar, 2011).
Furthermore, it is possible that the specimens assigned to E. lancensis actually represent more than a single species, but only more work and more complete remains will be able to resolve this issue (Bhullar, 2011).
Due to the fragmentary nature of what is known, I cannot say for sure how closely it resembled modern Xenosaurus and thus it is difficult to make any inferences on behavior or ecology. However, its dentition (or at least that of E. serratus) does resemble that of modern Xenosaurus (Bhullar, 2011), which eat mainly invertebrates, though they will eat smaller lizards or other vertebrates when the opportunity arises.
I am sorry that there is not much more I can say, but I do not want to make large leaps and say things that are not true - to admit our ignorance is the first step in the quest for knowledge!
Acknowledgements:
Bhullar, S. 2011. The Power and Utility Of Morphological Characters In Systematics: A Fully Resolved Phylogeny of Xenosaurus and Its Fossil Relatives (Squamata: Anguimorpha). Bulletin of the Museum of Comparative Zoology 160(3): 65-181.
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