Redescription and Revised Classification Status of Abbreviata phrynocephali comb. nov. (Spirurida: Physalopteridae) from the Yarkand Toad-Headed Agama Phrynocephalus axillaris (Lacertilia: Agamidae).

The genus Abbreviata (Travassos 1920) is distributed worldwide, with lizards serving as the primary hosts. Although Pentadentoptera phrynocephali was previously classified within Pentadentoptera, its original description lacked conclusive morphological and molecular evidence. Notably, key diagnostic features (such as oral dentition structure and spicule ratio) conform to the taxonomic criteria of Abbreviata. These ambiguous characteristics necessitate taxonomic reassessment to resolve systematic uncertainties. In this study, specimens of P. phrynocephali were collected from the stomachs of Phrynocephalus axillaris. Based on an integrated taxonomic approach, we provide detailed morphological redescriptions. We also conducted comparative morphological analyses with congeneric species of Pentadentoptera and Abbreviata. Molecular phylogenetic reconstruction was performed using Bayesian inference based on mitochondrial COI gene sequences. Diagnostic characteristics of this nematode include densely arranged denticles flanking the apical tooth base on the pseudolabial inner margin, a right spicule approximately half the length of the left spicule in males, a caudal region with four pairs of pedunculated papillae, six pairs of sessile papillae, one large unpaired papilla, and a hexadidymous uterus in females. These features distinctly differentiate the species from Pentadentoptera and align it with Abbreviata. Combined morphological and molecular evidence supports the reclassification of P. phrynocephali as Abbreviata phrynocephali (Tao 1985) comb. nov. (Spirurida: Physalopteridae).