Are Modern Cryptic Species Detectable in the Fossil Record? A Case Study on Agamid Lizards.

This article investigates the taxonomic and ecological classification potential of isolated skull bones—specifically frontals and maxillae—in Australo-Papuan agamid lizards (subfamily Amphibolurinae) using 3D geometric morphometrics. The study finds that these bones reliably distinguish genera and infer microhabitat use but have limited power to resolve species-level diversity, likely underestimating cryptic species richness in the fossil record. It also demonstrates that classification accuracy and morphological disparity estimates are influenced by sample size, ontogenetic variation, and specimen completeness, with missing data reducing species-level resolution more than genus-level or ecological assignments. The results highlight the challenges of applying modern molecular-based species delimitations to fossil osteological material and emphasize the need for appropriate morphological groupings when comparing extant and extinct biodiversity, suggesting that quantitative morphometric approaches can improve objective fossil classification and support conservation paleobiology.