Phetia, Korshunova & Fletcher & Martynov, 2025

Phetia gen. nov.

( Figs 1, 4)

urn:lsid:zoobank.org:act:41C28779-E6FB-4524-8CBF-

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Type species: Piseinotecus soussi Tamsouri et al., 2014 .

Etymology: After a shorter variant of spelling ‘Phetida’ attributed to the Ancient Greek sea goddess, Thetys , in reference to the ancient ocean, Thetys , which includes the modern Mediterranean Sea, to denote the Thetys-related origin of the new genus.

Diagnosis: Body moderately narrow. Notal edge completely reduced. Cerata on indistinct stalk-like derivations of former notal edge. Rhinophores smooth. Anterior foot corners present. Anus pleuroproctic. Central teeth with narrow non-compressed cusp and distinct denticles, some cusps forked. Lateral teeth absent. Proximal receptaculum seminis. Moderately long vas deferens with very distinct, thickened non-granulated prostate. No external penial collar. Accessory gland absent. Penis conical, with a long, sabre-shaped curved stylet.

Species included: Phetia soussi ( Tamsouri et al., 2014) comb.nov. [original description in Tamsouri et al. (2014); for corrected morphological data see present study, Fig. 4].

Remarks: The new genus Phetia gen. nov. forms a distinct, maximally supported (PP = 1, BS = 100) separate clade, sister to all known tropical true Unidentia ( Figs 1, 2). Uncorrected COI p -distances within the Phetia soussi comb. nov. clade are 0–0.17%. The COI minimal uncorrected p -distance of 15.4% was found between Phetia soussi comb. nov. and Unidentia sandramillenae , and 17.4% between P. soussi comb. nov. and Pacifia goddardi .

Phetia gen. nov. clearly is morphologically different from the genus Unidentia View in CoL by the presence of indistinct stalk-like modifications of the former notal edge with the cerata ( Fig. 4), instead of elongated elevations (which are an integral part of the dorsal side) characteristic of true Unidentia View in CoL , as well as a peculiar long, sabre-shaped copulative stylet. Importantly, in the first description of ‘ Piseinotecus ’ soussi ( Tamsouri et al. 2014) View in CoL the main pattern of the reproductive system was fundamentally incorrect, and in the present study we present correct information ( Fig. 4). Specifically, in Tamsouri et al. (2014: 995, fig. 3) the distinct prostate and part of the penial sheath were mistakenly identified as ‘bursa copulatrix’, whereas the peculiarly long copulative stylet ( Fig. 4G, H, I of the present study) was overlooked and the penis was described as ‘unarmed’. In reality the so-called ‘bursa copulatrix’ is the massive distinct prostate and penial sheath that contains the penis with its highly peculiar, long, curved, sabre-shaped stylet, which may easily be broken during preparation due to its length ( Fig. 4H). This has created a distorted picture of the key internal features of ‘ Piseinotecus ’ soussi View in CoL and further influenced its incorrect genus and family placement. Here we, therefore, present the correct details of the reproductive system of Phetia soussi , along with a description of its distinct prostate and peculiar stylet ( Fig. 4). The molecular data for the specimens in our study match the specimens of ‘ Piseinotecus ’ soussi View in CoL available from GenBank 100%. Phetia gen. nov. is, so far, restricted exclusively to the Mediterranean Sea and neighbouring localities, and shows both morphological and molecular distinctness from the tropical genus Unidentia View in CoL , indicating the Thetys-related origin of this new taxon.