Regalecus russelii Cuvier 1816
Creators: name: Angulo, Arturo
name: López-Sánchez, Myrna I.
Publisher: name: Zenodo
Year: 2017
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Actinopterygii
Lampriformes
Regalecidae
Regalecus
Regalecus russelii

description: Regalecus russelii (Cuvier 1816) — REGALECIDAE   
Oarfish (En); Pez remo (Sp)  
(Figure 2, Tables 1 and 3)  
 Material examined. 1 specimen (UCR 2478.001); adult, 3379 mm TL, 3353 mm SL, collected in the Gulf of Papagayo, Costa Rica, eastern Pacific Ocean, 10° 45' 0" N, 85° 42' 0" W, on 12 September 1995, by Mike Bragg on board of the Don Roberto vessel, found floating on surface.   
 Diagnostic characters. A member of Regalecidae in congruence with the diagnostic characters listed for the family in Heemstra (1986c), Olney (2003e), Nelson (2006) and Roberts (2012). Generic and specific diagnostic characters are listed below, all in accordance with descriptions of specimens by Chávez-Ramos et al. (1985), Castro-Aguirre et al. (1991, as R. kinoi), Salazar-Hermoso et al. (1999), Schmitter-Soto (2008), Ruiz & Gosztonyi (2010) and Roberts (2012).   
 Premaxilla not extending forward along dorsal profile of head (vs. extending forward along dorsal profile of head in Agrostichthys parkeri); axis of maxilla not oblique (vs. oblique in A. parkeri); dorsal-fin origin located ahead middle of eye (vs. behind of middle of eye in A. parkeri); first four dorsal-fin rays forming a double crest (vs. not forming a single or double crest in A. parkeri); total gill rakers on first gill arch 51 (vs. 6–10 in A. parkeri and 33–47 in R. glesne); dorsal-fin rays 323 (vs. more than 390, usually 400–450, in R. glesne); dorsal-fin rays until end of abdomen 77 (vs. 90–120 in R. glesne); first dorsal fin crest with three rays (vs. 6–8 in R. glesne); second dorsal fin crest with a single ray (vs. 5–11 in R. glesne; Heemstra 1986c, Olney 2003e, Roberts 2012).   
 Description. Measurements and counts, as well as comparative data, are presented in Table 3. Body highly elongate, ribbon-like, robust, and without scales, but covered by dermal tubercles with circular bases, either with or without a conical or blunt point, more visible and conspicuous at the ventral region and lower sides of the body. Predorsal profile concave, dorsal profile sloping down evenly and in a straight line from the forehead, before the eye, to the caudal region; ventral profile nearly straight (parallel with the body axis) for almost its entire length; posterior to anus, the dorsal and ventral profiles gradually converge forming an elongate and tapered tail. Maximum body depth about two head lengths before pectoral-fin origin.   
Head length about 19% of snout-vent length; snout length about 192% of eye diameter. Dorsal-fin origin anterior to center of orbit; first four dorsal-fin rays elongated, but broken (the second fin ray about 20% of SL, the third about 21% and the fourth about 15%), subsequent rays relatively short, becoming longer toward the middle region of the body, with the maximum height of fin anterodorsal to the anus; cristophore (see Roberts 2012) present and supports the first dorsal fin crest; pectoral fins low, originating anterior to pelvic-fin origin and their base horizontally oriented, allowing the fin to be vertically oriented when addressed against the body; pelvic fins with a single elongated, but broken, robust ray; caudal fin absent.  
Color in live (see Figure 2) silvery reddish grey with a silvery light brown head, ocular globes creamy, iris dark and pupils clear; first dorsal-fin rays, dorsal-fin membranes and pelvic-fin rays red; other rays white; 3–5 bands of conspicuous irregularly distributed and variably sized dark spots on the flanks. Color in alcohol light brown, with the anterior region of head darker and flanks with numerous dark spots, distributed as described above.  
 Remarks. Roberts (2012), in his monograph of the oarfish genus Regalecus Ascanius, 1772, recognized only two valid species: R. glesne and R. russelii. The author provide a complete diagnosis of both species that can be clearly separated by differences in several meristic and morphometric characters. The species R. kinoi, originally described from Baja California Sur, Mexico, represents, given this and as previously suggested by other authors (e. g. Salazar-Hermoso et al. 1999), a junior synonym of R. russelii (Roberts 2012).   
inconspicuous) or unavailable are representeđ with an en-đash (Q).  
  Chávez-Ramos et Castro-Aguirre et Salazar-Hermoso Schmitter-Soto Ruiz & Gosztonyi Character UCR 2478.001 al. (1985) al. (1991±) et al. (1999) (2008) (2010) Morphometrics    
 Our specimen of R. russelii represents, on the basis of Bussing & López (1994, 2005, 2009, 2011), the first documented record of the species in lower Central American (Costa Rican) Pacific waters and, on the basis of Ramírez-Murillo & Schmitter-Soto (1996), Roberts (2012) and Froese & Pauly (2016), a southeast range extension of about 1800 km (straight line) on their known distribution in the eastern Pacific Ocean; the southermost documented record for this species in eastern Pacific waters was on the central coast of Mexico (Ramírez-Murillo & Schmitter-Soto 1996; as R. kinoi).
description: Published as part of Angulo, Arturo & López-Sánchez, Myrna I., 2017, New records of lampriform fishes (Teleostei: Lampriformes) from the Pacific coast of lower Central America, with comments on the diversity, taxonomy and distribution of the Lampriformes in the eastern Pacific Ocean, pp. 573-591 in Zootaxa 4236 (3) on pages 579-582, DOI: 10.11646/zootaxa.4236.3.11, http://zenodo.org/record/322327