Is morphological-based taxonomy still effective in modern times? A response to Parrinha et al. (2025)

We reevaluate the recent species description of Holaspis ngalangi from Angola by Parrinha et al. (2025), which was based solely on variable morphological characters, through comparative analysis of specimens across the genus’ range, including material previously examined but not reported by the original authors. Our analysis demonstrates that the proposed diagnostic traits of this species (precloacal scale morphology and ventral scale arrangement) are hyper­variable within both H. guentheri and H. laevis, showing neither biogeographic nor morphological consistency. Notably, specimens from Angola’s Dundo Museum, though examined by Parrinha et al. (2025), were omitted from their analy­sis despite exhibiting the same variable characteristics, strongly indicating these represent intraspecific variation rather than diagnostic species-lineage features. Consequently, we formally place Holaspis ngalangi Parrinha, Marques, Gon­çalves, Tuitenko, Bauer & Ceríaco, 2025 as a junior synonym of Holaspis guentheri Gray, 1863, representing the sec­ond recent case of an Angolan reptile species description based solely on morphological data being synonymised within the last decade. These repeated cases highlight the inherent risks of morphology-only taxonomy, particularly when: (1) diagnostic characters show extensive overlap among taxa, and (2) multiple lines of evidence are not incorporated. Our findings also emphasize the critical need for robust, integrative species delimitation approaches in understudied regions like Angola, where high levels of cryptic diversity and phenotypic plasticity are likely to complicate taxonomic assess­ments.