A new leiognathid record from China with complete mitogenomes and phylogenetic insights of two Aurigequula (Teleostei, Leiognathidae) species

The ponyfish genus <i>Aurigequula</i> is a relatively poorly studied group within the Leiognathidae, with its diversity and phylogenetic relationships in the West Pacific remaining unclear. This study reports the first confirmed record of <i>Aurigequula striata</i> from Chinese waters, based on two specimens obtained from a fish market in Sanya, Hainan Island. Newly collected specimens of <i>A. fasciata</i> from the same region are also provided, which enabled detailed morphological and genomic analysis. The morphological descriptions are supplemented by detailed photographic documentation of fresh and preserved specimens, addressing the historical scarcity of reliable visual references for these species. Furthermore, we present the first complete mitochondrial genomes for both <i>A. striata</i> (16,629 bp) and <i>A. fasciata</i> (16,537 bp). Our phylogenomic analysis, based on 13 protein-coding genes, strongly supports the monophyly of the subfamilies Gazzinae and Leiognathinae. Within Leiognathinae, however, the analysis suggests paraphyly of <i>Aurigequula</i>, with <i>A. fasciata</i> forming a clade with <i>Leiognathus equula</i> to the exclusion of <i>A. striata</i>. This result conflicts with the current morphology-based generic diagnosis, which relies on consistent differences in the length of the second dorsal-fin spine and body coloration patterns. This study significantly expands the genomic resources for the understudied genus <i>Aurigequula</i> but also highlights the limitations of relying solely on mitochondrial data for resolving generic-level relationships. A more robust phylogenetic framework for Leiognathidae, capable of reconciling molecular and morphological evidence, will require the integration of multiple independent nuclear loci.