Caligus tenuis ( Leidy, 1889 )

Boxshall, Geoffrey A. & Bernot, James P., 2023, Resolving taxonomic and nomenclatural problems in the genus Caligus O. F. Müller, 1785 (Copepoda: Caligidae), Zootaxa 5360 (4), pp. 545-567 : 562

Caligus tenuis ( Leidy, 1889)

Özak et al. (2017) concluded that the genus Sciaenophilus van Beneden, 1852 was a synonym of Caligus and transferred all four of its species. The type species Sciaenophilus tenuis van Beneden, 1852 became Caligus tenuis (van Beneden, 1852) . This transfer created a secondary homonym since the name Caligus tenuis ( Leidy, 1889) was used by Fowler (1912). This homonymy has not been addressed.

Leidy (1889) originally established a new species of caligid as Chalimus tenuis Leidy, 1889 based on a single unidentifiable chalimus stage. By this date it was quite widely accepted that the chalimus was merely a developmental stage of caligids (e.g., Krøyer, 1837) and the generic name Chalimus Burmeister, 1835 had largely fallen into disuse. However, Fowler (1912) in his “ Crustacea of New Jersey ” listed the genus Chalimus as a synonym of Caligus and transferred Leidy’s species, thereby creating the new combination Caligus tenuis ( Leidy, 1889) . This taxon has incorrectly been attributed to Fowler (1912) although Fowler was responsible only for the new combination.

The type specimen, an early chalimus stage found by Leidy (1889), was obtained from the tail fin of a larval fish, Leptocephalus sp. The description available is minimal with a single dorsal habitus view showing no rudiments of lunules or any trace of ecdysial extension lobes, typical of many Caligus species. We conclude that there is no robust evidence supporting the transfer of Chalimus tenuis to Caligus as it could equally well belong to another caligid genus. We therefore reject this transfer. Chalimus tenuis Leidy, 1889 remains a species inquirendum within a genus which is no longer regarded as valid.