The misuse of morphometrics multiplies the number of invalid names: the case of <i>Yoldiella lapernoi</i> and <i>Yoldiella paranapuensis</i> (Mollusca, Bivalvia)

Abstract The family Yoldiidae encompasses protobranch bivalves with notable diversity in deep-sea habitats, with Yoldiella Verrill and Bush (1897) as the most speciose genus. In Brazilian waters, 11 species of Yoldiella have been recorded, including Yoldiella lapernoi Benaim and Absalão (2011) and Yoldiella paranapuensis Benaim and Absalão (2011), two species with similar shell morphology and overlapping geographical distributions. This study re-evaluated the taxonomic distinction between these two Yoldiella species using a combination of morphometric approaches. Size and growth rate comparisons were conducted using analysis of covariance and Bayesian model selection. The shell outline was compared using elliptical Fourier descriptors. The results did not support the current separation of these taxa. Instead, they reveal that the observed morphological differences are attributable to ontogenetic variation, indicating Y. paranapuensis as a juvenile stage of Y. lapernoi . This finding supports the synonymy of these two nominal species and highlights the importance of ontogenetic context in taxonomy.