Tylocarcinus styx

Tylocarcinus styx (Herbst, 1803) Fig. 44 Material examined MAURITIUS • 1 unsexed (12.6× 19.2); 1850?; belonging to the “Sala del Mar” exhibition; MNCN20.04/00192. Remarks This specimen belonged to the exhibition of the Sala del Mar, being dry preserved inside a glass and wooden box, without retaining any old label. It is currently identified as Apiomithrax violaceus (A. Milne-Edwards, 1867), originating from the waters of the Cabo Verde Islands. However, this specimen is not A. violaceus, nor is there any species or genus with similar characteristics in the waters of West Africa. The specimen belongs to the species Tylocarcinus styx (Herbst, 1803) which has an Indo-Pacific distribution, as do all species of this genus. This led us to question whether the origin of this specimen was truly Cabo Verde, or perhaps it came from Indo-Pacific waters. In the current records and for many years now, the only data we can obtain about this specimen is that it comes from Cabo Verde, with no collector’s name or year of collection, and a comment where a number supposedly from a catalogue appears, but we have not been able to determine what it corresponds to. Reviewing the inventory files and catalogues of the historical collections of the MNCN, an inventory by San Miguel de la Cámara in 1911 (ACN0248/005), was found, in which a specimen that could be our specimen appears. On page 22 of said catalogue (Fig. 45C–D), a specimen with an almost crossed-out name appears, where “ Arctopsis Styx Herbst from Île de France (current Mauritius), collector Guérin”, can be read, and just below this, the name Micropisa violacea from Cabo Verde (Fig. 45D). We believe that the crossing out of the name, the accompanying date, and the arrangement of the data caused the confusion that has persisted to this day, leading to the assumption that this specimen was the species Micropisa violaceus (today labelled as Apiomithrax violaceus), and that it originated from the waters of Cabo Verde. Since that date in 1911 when San Miguel de la Cámara made his notes about these specimens, this specimen has been considered to originate from the waters of Cabo Verde. However, it is now demonstrated that this specimen comes from the waters of Mauritius and was collected by Guérin-Méneville in 1850. For identification, see also Sakai (1938), Griffin & Tranter (1986) and Poore & Ahyong (2023).