Birdsongichthys Tornabene, Manning, Robertson, Tassell & Baldwin, 2023, SP. NOV

BIRDSONGICHTHYS RECTUS SP. NOV. (FIGS 4A, 5–7) Straightfinned goby (English), gobio de aleta recta (Spanish). Gobiidae genus 2, species 1 Robertson et al., 2020: table 1, supplemental plate S13. Zoobank registration: urn: lsid: zoobank. org:act: 016EDDA3-572B-45CB-8B05-676076400186 Holotype: USNM 442874, 14.1 mm SL female, tissue EUS17221, field number CURASUB 17-21, 151 m depth, rubble patch, south and south-east of R / V Chapman mooring, SW of island, Kay Bay, Sint Eustatius, 17.4566, –62.9791, quinaldine, HOV Curasub and R / V Chapman, Carole Baldwin, Luke Tornabene, Bruce Brandt, 19 April 2017. Table 1 . Continued * genus is not monophyletic. ** See Birdsong et al. (1988) for wide range of vertebral counts and pterygiophore insertion patterns. Abbreviations : D 1, first dorsal fin ; D 2, second dorsal fin; A, anal fin; AP , anal fin pterygiophores. Paratypes: MUVS-V-439, 21.0 mm SL male, tissue ROA18021, field number IDABEL18-01, 213 m depth, sand and limestone rubble, outside Halfmoon Bay, Roatan, Honduras, 16.304384°, –86.598204°, quinaldine sulphate, HOV Idabel, D. Ross Robertson, Rachel Manning, Karl Stanley, 4 June 2018; UW 158074, 18.3 mm female, tissue ROA17004, cleared and stained, field number IDABEL17-01, 192 m depth, outside Halfmoon Bay, Roatan, Honduras, 16.305557°, –86.597669°, quinaldine sulphate, HOV Idabel, Luke Tornabene, Ross Robertson, Karl Stanley, 24 July 2017; UW 158128, 12.0 mm female, tissue ROA18044, field number IDABEL18-03, 241 m depth, sand rubble in rock hole, 16.3043°, –86.5982°, quinaldine sulphate, HOV Idabel, Luke Tornabene, Rachel Manning, Karl Stanley, 6 June 2018; UW 158200, 11.5 mm male, tissue ROA18212, field number IDABEL18-08, 213 m depth, sand at base of limestone, 16.3043°, –86.5982°, quinaldine sulphate, HOV Idabel, Luke Tornabene, Katherine Maslenikov, Karl Stanley, 1 June 2018; USNM 442726, 14.4 mm male, tissue EUS17073, field number CURASUB 17-18, 110 m depth, rubble and sand on wall, dropoff west of R / V Chapman mooring, Gallows Bay, Sint Eustatius, 17.4608°, –63.0179°, quinaldine, HOV Curasub and R / V Chapman, Carole Baldwin, Luke Tornabene, Barbara van Bebber, Jordan Casey, 16 April 2017. Diagnosis: Birdsongichthys rectus is the only known member of the genus, so the species diagnosis is that of the diagnosis of the genus. Description: Morphometric data are presented in Table 2. Median and paired fins: first dorsal fin VII(6), first spine extremely elongate in some specimens, extending posteriorly to point between middle of soft dorsal fin and base of anal fin when flat against body; second dorsal fin I,8*(1) or I,9(5); anal fin I,8*(6); pectoral-fin rays 16*(3), 17 (2), 18(1), extending posteriorly to a vertical through second dorsal-fin ray 2 or 3; pelvic fin I,5* (5), all rays unbranched; pelvic fins well separated, lacking anterior frenum, membrane connecting fifth rays absent or reduced; fourth and fifth pelvic-fin rays approximately equal in length, extending posteriorly to base of anal-fin rays 6–7; tips of pelvic-fin rays not ending in fleshy pads; caudal fin truncate or emarginate; branched caudal-fin rays 12 (4)*, segmented caudal-fin rays 17(5)*, caudal fin broken in many specimens. Scales: Scales on head and nape absent; ctenoid scales on side of body present starting above pectoral fin and continuing to caudal peduncle; lateral scale rows 22–23, transverse scale rows 5, scales counted from three specimens including holotype, scales lost in other specimens; pair of modified ctenoid scales with enlarged cteni present at base of caudal fin, one each at dorsal and ventral margins of fin (Fig. 5); abdomen and chest each with small patch of ctenoid scales. Head: Jaw extending posteriorly to a vertical through anterior margin of eye or midpoint of pupil; anterior naris a short tube, posterior naris an opening flush with snout; cephalic lateralis pores small, pores B′, D(s), E′ present in four specimens, pores B′ extremely small and pore D missing in holotype, pores B′ not visible in paratype UW 158200; eyes large, 30–36% HL, positioned dorsolaterally. Upper jaw with two to three rows of teeth anteriorly, outermost row enlarged widely spaced canines continuing along entire upper jaw to the end of the premaxilla, innermost two rows tightly packed, shorter, and conical, becoming single row posteriorly; lower jaw with three to five rows of teeth anteriorly, outermost row restricted to tip of dentary and slightly larger than innermost rows, innermost rows becoming two rows posteriorly. Sensory papillae not visible on most specimens due to small size of specimens and damage to the face from collection. Genitalia: Male urogenital papilla elongate and pointed; female urogenital papilla short, bulbous or slightly conical. Colour in fresh specimens (Fig. 6): Side of body translucent with iridescent scale margins; three horizontal rows of small, bright yellow spots along flank, spots largest in the bottom row; first row with 12–15 spots starting on nape and continuing along dorsal midline, ending just anterior to caudal-fin base; second row with 13–15 spots starting above pectoral fin and continuing along lateral midline, ending just anterior to caudal-fin base; third row with eight to nine spots starting just anterior to anal-fin origin and continuing along ventral midline, ending just anterior to caudal-fin base; tips of snout and upper and lower jaws with small patch of yellow; eye with upperhalf of iris black, lower-half yellow; a broad, oblique yellow to orange stripe extending from lower-rear part of iris down on to preopercle; remainder of head translucent; pink coloration of red gill arches visible through operculum; pectoral-fin base with yellow spot on yellow upper margin of some specimens; dorsal fins with uniform translucent yellow wash with scattered iridophores, and with a distinct horizontal series of yellow spots along midpoints of spines and rays in some specimens; pectoral fins pale or uniformly translucent yellow; caudal fin faintly translucent yellow with two dark yellow, vertical bars at base; anal and pelvic fins uniformly translucent yellow. Colour in preservation (Fig. 7): Body uniformly pale yellowish, no dark pigmentation remains in any preserved specimens, including those fixed either in 95% ethanol or in formalin followed by storage in 70–75% ethanol. Habitat: Known from 110-241 m depth on sand and rubble substrates situated on or around the base of walls or steep rocky slopes on deep reefs. Distribution: Known from Roatan, Honduras and Sint Eustatius, Caribbean Netherlands. Etymology: The epithet is from the Latin adjective rectus, straight, which refers to the straight, unbranched rays of the pelvic fin.