A new fossil agnathan, Turinia antarctica sp. nov., based on numerous isolated scales, comes from the lower fish-bearing beds of the Aztec Siltstone. Scales from moraine at Mount Suess, originally described as selachian or psammosteid heterostracan, are referred to the new species which shows close affinity with T. gondwana from Bolivia and T. cf. hutkensis from Iran. Reassessment of the biostratigraphy of Middle Devonian turiniid scales suggests that the lower part of the Aztec Siltstone may be of Eifelian age.