Minami-hyomon-umiushi finally gets a scientific name — and a tangle of Japanese vernaculars

Minami-hyomon-umiushi now has a formal scientific name:

Jorunna daoulasi Innabi, Stout & Á. Valdés, 2023

https://zookeys.pensoft.net/article/98258/

But to make sense of that, we need to first untangle:

• What is "minami-hyomon-umiushi" anyway?
• Isn't minami-hyomon-umiushi supposed to be in Rostanga (iso-umiushi genus), not Jorunna (gomafu-bilord-umiushi genus)?
• What actually distinguishes Rostanga from Jorunna?

The Japanese vernacular "minami-hyomon-umiushi" was coined in Sea Slugs of Okinawa (2004). But in fact, Baba Kikutaro had already applied that vernacular in 2000 — to a different animal.

However, the most recent paper (Kashio et al. 2021) treats the greenish animal here as the species for which the vernacular "totoro-umiushi" had been proposed by Hori and Fukuda (1996).

So: Baba's "minami-hyomon-umiushi" becomes a junior synonym; "totoro-umiushi" wins.

Which then frees up "minami-hyomon-umiushi" for use in Sea Slugs of Okinawa — where Ono had reused the name for what he thought was Baba's species, but it turned out to be a different species entirely. (Ono saw what Baba had labelled "minami-hyomon-umiushi", thought "ah, this is that animal", and re-applied the vernacular — except they weren't the same animal.)

To add yet another layer: in 2016, Nudibranchs of Japan proposed "murasaki-amime-umiushi" as another new vernacular, and that has its own complications.

Side rant:

People assume "the first name applied wins" — but that rule is the rule for scientific names under the ICZN. The first scientific name applied is the valid one, and later names become synonyms.

What about Japanese vernaculars?

There are basically no rules.

For fish and insects, the relevant academic societies set rules. For sea slugs (and molluscs broadly) there are no such rules and no central body cataloguing/standardising Japanese vernaculars, so no "standard Japanese vernacular" actually exists.

On seaslug.world we run by approximate convention:

• Try to honour the earliest-applied vernacular (so it's still sesuji-umiushi, not ribbon-iro-umiushi)
• Don't rename a vernacular just because it no longer matches the genus or species characters (so Thompson awatsubu-gai doesn't get renamed to kotori-gai)