I have been aware of the work presented here for a couple of years and it's nice to see it come to completion. The work is sound (and a good illustration of the phenomenal ability of tomographic techniques to solve previously intractable riddles in morphological palaeontology), the manuscript is well written and well illustrated, and I agree with the conclusions. There are only a few, very minor, issues to raise with the authors:

Line 35: Why are the first two references given in long format rather than as numbers?

Line 45: The citation of Kuratani & Ahlberg 2018 (ref. 16) here is slightly misleading, because that paper only deals with the composition of the head and does not address feeding strategies. The two jawless stem gnathostome groups featured in that paper, galeaspids and osteostracans, are generally regarded as bottom-feeding detritivores.

Lines 170 and 175: Why is Tarlo 1961 not given a reference number here?

Line 247 onwards: One obvious interpretation of the double-arched profile of the dorsal margin of the mouth is that it accommodated separate water intakes to the left and right nasal sacs, somewhat the manner of the anterior nostrils of lungfishes, which lie right on the upper lip. This would fit with the evidence from heterostracan dorsal shield endocasts for well-separated nasal sacs. Maybe it would be worth commenting on this possibility?

Lines 384-386: In addition to this argumentation, which I agree with, I would draw your attention to the position of the orbits: they are low on the sides of the face, positioned below the level of the mouth opening, and oriented slightly downwards. This is not at all what you would expect from a bottom-feeder, as the eyes would be shoved into the sediment during feeding and could suffer injury; the contrast with the emphatically dorsal eye position in osteostracans and galeaspids is quite telling. Rhinopteraspis must have been active in the water column, and if the eye position is informative it may have operated quite near the surface while keeping an eye on things below.

Once these points have been addressed, I believe the manuscript will be ready for publication.