The book's Goniodoridella unidonta is not unidonta (the identification, and what COI can and cannot say)

The specimen the book identifies as Goniodoridella unidonta is, at least, not unidonta. The book identified an Okinawan specimen as G. unidonta and proposed a new Japanese vernacular name for it. But when we re-measured the COI of that same specimen, it sits far from the unidonta sequences and is closest to the type-derived sequence of G. geminae. The unidonta identification does not hold.

How the identification was overturned

The sequence of events is as follows.

1. Paz-Sedano et al. 2023 described three new species (geminae / serrata / unidonta) in Goniodoridella and deposited COI sequences on GenBank as OQ363855-58. But the authors did not file for release, and the sequences stayed private
2. The book (Imagawa 2026) identified an Okinawan specimen as G. unidonta and proposed a new Japanese vernacular name for it (the editing period appears to be around 2024–2026)
3. This site, before the book's release, saw from the published photo that the specimen looked closer to G. geminae than to G. unidonta. But even measuring the COI, the crucial comparison sequences were private, so it could be judged neither unidonta nor geminae; the closest available sequence was only 87%, with other genera lined up at 85–87%
4. This site asked the authors of Paz-Sedano to release the sequences, and OQ363855-58 were made public on 9 June 2026
5. This site re-measured the Okinawan specimen against the released sequences and settled the identification on 12 June

The result after re-measuring

We assembled the released OQ363855-58 together with existing sequences and re-measured the Okinawan specimens by COI.

SSWBP483 / 248, the specimens the book treated as G. unidonta, sit 14.6–15.3% away from G. unidonta against the released sequences — far beyond a between-species distance, so the unidonta identification does not hold. Against the type-derived sequence of G. geminae, on the other hand, they differ by only 1.07%, within the range of intraspecific variation. This is a match to the type, not merely to a label, and as far as COI goes it can be taken as G. geminae with near certainty.

Okinawa has at least three Goniodoridella lineages

The book also proposes a new Japanese vernacular name for a second Okinawan Goniodoridella. Even against the released sequences, this one fits none of the described species.