Uncisudis Maul, 1956

Uncisudis Maul, 1956 View in CoL

Uncisudis Maul, 1956:91 View in CoL ( type species: Uncisudis longirostra Maul, 1956 View in CoL ; by monotypy).

Pontosudis Rofen, 1963:4 View in CoL ( type species: Pontosudis advena Rofen, 1963 View in CoL ; by monotypy).

Diagnosis. A genus of subfamily Lestidiinae with a relatively short body; head, snout and jaws relatively long compared to the short body in all sizes; nostrils directly above or slightly behind posterior end of maxilla; anus immediately behind pelvic-fin base; a well-developed ventral adipose fin between anus and anal-fin origin; and relatively low vertebrae count (75–80). Blotches usually present on dorsum and anal fin in juveniles but absent in adults. No luminous organs around eye, abdominal surface and inside abdominal cavity.

Distribution. Based on Global Biodiversity Information Facility (https://www.gbif.org/), Uncisudis are widely distributed in tropical to temperate seas in all three major oceans, with adults recorded from the Atlantic Ocean. Uncisudis longirostra is found mostly in the Atlantic Ocean, with some scattered records in the Pacific and western Indian oceans; U. quadrimaculata is found only in the Atlantic Ocean; U. advena is found in all three major oceans but absent in the eastern Pacific; and U. posteropelvis is found in the northern Pacific Ocean. Lanam (2022: 83) indicated that “all [ U. longirostra , U. quadrimaculata , U. advena ] [are found] within the warmer waters near the equator. None of the species are in the colder oceans. Uncisudis advena has strong populations along the west coasts of the Atlantic Ocean while the other two species… do not follow the coasts as closely.” According to our observation, Uncisudis posteropelvis which was known only from juveniles (not treated in Lanam 2022) has a similar distribution pattern to U. advena .

Remarks. There are currently four valid species recognized in Uncisudis . The species are rather similar in general appearance, pigmentation, and share similar meristic counts. Although their differences are minor, the relative positions of pelvic, dorsal and anal fins seem to be important for identifying species. Because almost all specimens documented are juveniles, no complete information on their lateral-line scale and vertebral counts are available, adult specimens are needed to better understand these species.

Key to species of Uncisudis View in CoL

1A. Pelvic-fin origin well posterior, close to anal fin............................. U. posteropelvis View in CoL (northern Pacific Ocean)

1B. Pelvic-fin origin slightly before or below dorsal-fin base...................................................... 2

2A. Pelvic-fin origin below dorsal-fin base; anus slightly behind posterior end of dorsal fin base.... U. advena View in CoL (all major oceans)

2B. Pelvic-fin origin slightly before dorsal-fin origin............................................................ 3

3A. Anus below dorsal-fin origin...................................... U. quadrimaculata View in CoL (Atlantic and Pacific oceans)

3B. Anus behind a vertical through dorsal-fin origin.................................... U. longirostra View in CoL (all major oceans)