A New Species of Hagfish Eptatretus rubicundus (Myxinidae: Myxiniformes) from Taiwan, with Reference to Its Phylogenetic Position Based on Its Mitochondrial DNA Sequence

A new species of hagfish, Eptatretus rubicundus sp nov., collected from the northeastern coast of Taiwan is described. Eptatretus rubicundus sp. nov. was diagnosed by the branchial slime pores and gill apertures arranged in a straight line, the distances from a branchial pore to its immediate preceding and posterior gill apertures were similar; the ventral aorta was not bifurcated; and the combination of the following characters: 5 pairs of gill pouches and gill apertures, gill apertures not crowded, 100-104 total slime pores including those in the branchial region, branchial ducts of approximately the same lengths, the pharyngocutaneous-duct opening fused to the posteriormost left gill aperture, the 1st pair of afferent branchial arteries located between the 1st and 2nd gill pouches, a pair of low, round nasal papillae without supporting cartilage on the roof of the nasal tube, and a pink body. The mitochondrial 16S ribosomal RNA gene fragment sequences confirmed the most basal position of E. rubicundus sp. nov. in the Eptatretinae. Gene-sequence data on phylogenetic relationships of the species in the previously recognized genera of Quadratus, Paramyxine, and Eptatretus indicated that these genera are not all monophyletic and suggested that they should be combined into a single genus under the generic name Eptatretus.