Molecular phylogeny and new classification of the genera Eulophias and Zoarchias (PISCES, Zoarcoidei)

- Molecular phylogenetic analyses were conducted on the genera Eulophias and Zoarchias.
- Our analysis supported the monophyly of the suborder level of the Zoarcoidei.
- Two genera were clearly separated from each other as well as from other families.
- We suggest that the Eulophias belongs to a new family named as the Eulophiidae.
- The Zoarchias belongs to the family Neozoarcidae rather than to either the Stichaeidae or Zoarcidae.

Morphological and osteological studies of the Zoarcoidei group have previously been undertaken, but the group (especially the genera Eulophias and Zoarchias) still remains enigmatic. Therefore, we conducted molecular phylogenetic studies on the two genera Eulophias and Zoarchias using two mitochondrial (16S rRNA and COI) and two nuclear genes (RAG2 and RNF213). Our phylogenetic analysis supported the monophyly of the suborder level of the Zoarcoidei, but rejected the previous morphology- and osteology-based classification hypotheses regarding the two genera. Conflict between mtDNA and nDNA phylogenies within the genus Eulophias implies that the genus shows a complicated relationship such as hybridization in the process of the evolutionary history. The genetic distances between the Eulophias (or Zoarchias) and other Zoarcoidei spp. were the greatest, showing different family-level affiliations. In addition, the mtDNA topology showed the two genera were clearly separated from each other as well as from the families Stichaeidae and Zoarcidae. Considering the new molecular phylogeny, we suggest a new classification for the two genera: (1) Eulophias belongs to a new family named as the Eulophiidae; (2) Zoarchias belongs to the family Neozoarcidae (sensu Radchenko et al., 2012b) rather than to Stichaeidae and Zoarcidae.