Psednos carolinae, David L. Stein, 2005

David L. Stein, 2005, Descriptions of four new species, redescription of Paraliparis membranaceus, and additional data on species of the fish family Liparidae (Pisces, Scorpaeniformes) from the west coast of South America and the Indian Ocean., Zootaxa 1019, pp. 1-25 : 18-20

Psednos carolinae new species

(Fig. 6)

Holotype: USNM 381005, male, 39 mm SL, 45 mm TL, “Anton Bruun” Cruise 6, Sta. 351B #7352, 29° 55' S, 64° 58' E, mid-Indian Ocean, 28 June 1964, midwater trawl 0-350 m.

Diagnosis. A Psednos with unusually few vertebrae (38), coronal pore present, temporal pores two, mouth angle of about 90° to the horizontal, head length about 30 % of SL, snout to anus distance about 80 % HL, and pectoral fin of 14 (8+1+5) rays.

Description. Counts: D 33, A 26, P 14 (8+1+5), C 6, Vert. 38 (10+28), pores 2-5-6-2, coronal present. Proportions: head length 29.1 % SL, head width 17.0 (58.4), depth 28.9 % (99.1 % HL), snout 7.7 (26.5), premaxilla 13.9 (47.8), mandible 13.4 (46.0), eye 7.5 (25.7), gill opening 8.2 (28.3), snout to anus 23.7 (81.4), mandible to anus 24.6 (86.5), anus to anal fin 32.6 (112.4), predorsal length 29.1 (109.7), preanal length 46.6 (160.2), upper pectoral fin lobe 28.3 (97.3), lower pectoral fin lobe 22.2 (76.1).

Head large, its depth about equal to its length, a little more than half as wide as long. Mouth angle about 90° to horizontal, upper jaw slightly longer than lower. Prominent symphyseal knob present on lower jaw, on horizontal with middle of pupil; retroarticular process below front edge of eye. Teeth forming narrow bands in both jaws; upper jaw teeth tiny, mostly biserial, but about 5 oblique rows of about 4 teeth each present near symphysis. Lower jaw teeth much larger and more numerous than in upper jaw, thorn like, inner teeth slightly larger than outers; forming a narrow band 5 or fewer teeth wide, in either irregular oblique rows or not in rows. Symphyseal gap present in upper and lower jaws. Nostrils single, about on horizontal with upper margin of orbit. Eyes large, about one-fourth of head length. Gill openings completely above pectoral fins, angled strongly posteriorly, tip of the operculum protruding ventrally to form an obtuse angle but not a lobe. Length of opening slightly greater than eye diameter. To avoid damage, gill rakers not examined. Nasal pores 2, posterior pair very large, much closer together than anterior pair or nasal rosettes, above level of orbit, almost on top of head. Coronal pore present, large, on or slightly behind top of head, behind vertical through posterior margin of orbit. Chin pores very widely spaced, one on each side of symphyseal knob and distant from it by at least one pore diameter. Infraorbital pores 5 (anteriormost very small, located on anterior end of suborbital stay), preoperculo-mandibular pores 6, 3 on lower jaw, 3 on cheek. Two temporal pores present; one large, above and to the rear of orbit, one suprabranchial, well above gill opening.

Pectoral fins with 14 (8+1+5) rays, none rudimentary; notch deep, the notch ray distinctly separated widely from upper and lower lobe rays. Dorsal ray even with or below corner of mouth, ventralmost ray anterior, below middle or forward half of branchiostegal rays. Upper lobe longer than lower, of which the rays are free and extended. All rays of similar thickness.

Body moderately humpbacked, depth at occiput about one-fourth SL, depth at anal fin origin less than one-half head depth. Dorsal and anal fins low, overlapping caudal fin by about half. First dorsal ray inserted on fourth vertebra, first anal fin ray on tenth vertebra. Haemal spines of abdominal vertebrae gradually increasing in length posteriorly. Anus far anterior to gill opening, below or behind rear margin of orbit, almost between bases of lower lobe rays; a small blunt genital papilla present. Preanal length slightly less than half SL. Pyloric caeca not examined to minimize damage to specimen. Skin thin, transparent. Hypurals fused. Holotype is a ripe male.

Color of skin translucent white; peritoneum and muscles easily visible through skin. Mouth pale brown, gill cavity darker brown, peritoneum dark brown, stomach brownish.

Etymology. Named in honor of Caroline Ajootian, for her unfailing support and encouragement of snailfish research.

Distribution. Known only from the holotype taken in mid-Indian Ocean.

Remarks. Psednos carolinae is most similar to P. steini Chernova 2001 in having similar numbers of dorsal and anal fin rays, identical number and arrangement of pectoral fin rays, and many similar proportions, but differs significantly in the following characters: number of vertebrae (38 vs 41), mouth angle (90° vs 50°), longer head (29.1 % vs 24.5 % SL), relatively shorter distance from snout-anus (81.4 % vs 95.6 % HL), more anterior dorsal and anal fin origins (109.7 and 160.2 % vs 118.9 and 177.8 % HL), upper pectoral fin lobe longer than lower lobe (vs shorter), and body color (transparent white vs brown).

Psednos dentatus Chernova and Stein 2002 from off Chile is similar in appearance, but lacks a coronal pore and is easily distinguished from the new species by many characters, including numbers of vertebrae, dorsal, and anal fin rays (38 vs 46, 33 vs 39, 26 vs 34). Members of the “Australian” group of species lack a coronal pore and have at least 56 vertebrae.

The new species has the fewest vertebrae known of any in the genus. Chernova (2001) divided Psednos into two groups based on number of vertebrae, presence of a coronal pore, and number of infraorbital pores. Subsequently, Chernova and Stein (2002) described ten more species and defined three “natural” groups: the “ micrurus ” group with vertebrae 40-44, a coronal pore, and postorbital pore absent; the “ christinae ” group with vertebrae 46-47, a coronal pore absent, and a postorbital pore present; and an “Australian” group with vertebrae 56-58. Chernova and Stein (2004) described another species that fits in group 2. This specimen is in excellent condition, allowing clear conclusions regarding character states. Its few (38) vertebrae and lack of io6 place it in the “ micrurus ” group, now including species with 38-44 vertebrae. This is the fourth Indian Ocean species known, all of which have a coronal pore and presumably lack io6 (whether this pore occurs in P. micrurus is unknown).