A morphometric exploration of the taxonomic utility of scale osteoderms in southern African fossorial skinks (Acontinae, Acontias)

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This study investigates the morphometric variation of osteoderms across species and populations within the genus Acontias, especially in the A. meleagris species complex. Using both univariate and multivariate analyses, we evaluated whether size-independent osteoderm morphometrics could effectively differentiate taxa, particularly where minimal genetic divergence is present (i.e., cases where morphologically diagnosable species show little genetic separation). Univariate analysis revealed some significant morphometric variation across osteoderm regions, with sub-regions C and D showing the highest discriminatory power. Multivariate analyses, including principal component analysis (PCA) and discriminant function analysis (DFA), demonstrated the complementary strengths of ratio-based and studentized linearized residuals (SLRs)-based metrics. Ratio-based analyses were more effective in distinguishing genetic species, while SLRs-based analyses captured finer-scale population differences. The combined approach improved classification accuracy, underscoring the value of integrating multiple morphometric methods. Our results suggest that osteoderm morphometrics provide valuable supplementary data for species delimitation and may help resolve taxonomic boundaries within Acontias and possibly other lizards. However, the limited ability to differentiate morphs and populations in some cases highlights the need for additional data, such as environmental or behavioral traits. The findings have the potential to improve taxonomic resolution among skinks and contribute to broader taxonomic frameworks in herpetological systematics.

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