Photolateralis polyfenestrus, Sparks & Chakrabarty, 2019

Photolateralis polyfenestrus , new species

Figures 1 View FIG , 2 View FIG ; table 1

HOLOTYPE: AMNH 267152 , 66.8 mm SL, male; Sultanate of Oman: Gulf of Oman, Fish Market , 23 ° 36′ N; 058 ° 33′ E; Z. Baldwin, July 2008. GoogleMaps

DIAGNOSIS: Photolateralis polyfenestrus is distinguished from congeners by the presence of a short, composite midlateral stripe comprised of three small, rounded translucent windows that are peppered with chromatophores (vs. numerous windows in both P. stercorarius and P. moretoniensis , or a continuous translucent stripe in P. antongil ) and is confined to the midflank (vs. extending most to entire the length of the flank in congeners). The new species is further distinguished from both P. stercorarius and P. moretoniensis by a pigmentation pattern above the lateral midline comprised of larger rounded blotches and markings (vs. smaller sinuous lines and markings forming a vermiculate pattern), and both P. moretoniensis and P. antongil by a shallower body. Photolateralis polyfenestrus exhibits a lower jaw that is deep and convex in lateral view (vs. mostly straight in congeners, less P. antongil ), and that forms an angle of between 60 ° –70 ° to horizontal (vs. less than 45 ° in congeners, less P. antongil ). The only other species of Photolateralis reported from the western Indian Ocean is P. antongil , to date only known from the coastal waters of Madagascar, and whereas both P. stercorarius and P. moretoniensis have more extensive ranges, nevertheless they are restricted to the western Pacific and extending into the eastern Indian Ocean.

DESCRIPTION: Proportional measurements and meristic data presented in table 1 and internal osteological features can be visualized in figure 2. A moderately shallow-bodied and elongate leiognathid. Body laterally compressed. Lateral snout outline straight with a protuberance above upper lip. Mouth small and terminal in position. Premaxilla long and protruding along dorsal margin. Posterior margin of maxilla exposed, reaching to level of vertical through anterior margin of orbit. Lower jaw deep and noticeably convex in lateral view, forming angle of 60 ° –70 ° to horizontal. Mild preorbital protuberance due to protrusion of both frontal and lateral ethmoid ossifications. Predorsal head profile weakly sloping and straight. Nuchal spine (exposed rising dorsal aspect of the supraoccipital crest) very slightly protruding and distal tip exposed. Nuchal spine with distinct median keel. Eye large. Anterior nasal pore small and round; posterior foramen much larger and crescent shaped, partially encircling anterior pore. Two short and stout postnasal spines present on lateral ethmoid, located posterior to nasal foramina and just rostrodorsal of orbit. Postnasal spines followed posteriorly by well-developed supraorbital ridges that converge posteriorly. One supraneural present with strong anterior process. Preopercular margin smooth, not serrate, along ventral and ventrocaudal margins. Dorsal and ventral body profiles mildly rounded, with ventral profile more convex than dorsal. Dorsal-fin origin located well posterior to vertical through pelvic-fin origin. Anal-fin origin located at about level of vertical through the last (= 8th) dorsal-fin spine/first dorsal-fin ray. Caudal peduncle slender and shallow. Total vertebral count 23: 10 precaudal + 13 caudal. Neural and hemal spines of vertebral centrum PU4 weakly expanded distally and bladelike. Thirteen elongate and triangular outer gill rakers arrayed along lower limb (= 5th ceratobranchial) of first gill arch.

Fins: Dorsal fin with VIII spines and 16 branched rays. First dorsal-fin spine greatly reduced in length and somewhat robust. Second through fourth dorsal-fin spines elongate and robust; second spine longest. Second dorsal-fin spine moderately, but not exceedingly, elongate compared to third and fourth. Third and fourth dorsal-fin spines serrate along anterior margin “lock” into groove on posterior margin of preceding spine when erect (fig. 2). Dorsal-fin spines five through eight feeble, considerably shorter than second through fourth spines. Anal fin with III spines and 14 branched rays. First anal-fin spine very short. Second and third anal-fin spines robust and elongate. Third anal-fin spine serrate on anterior margin “locks” into groove on posterior margin of second spine when erect (fig. 2). Spinous dorsal and anal fins with asquamate basal sheath. Eighteen total pectoral-fin rays. Pelvic fins short, not reaching first anal-fin spine when adducted (i.e., a significant gap present). Eight upper and seven lower branched caudal-fin rays.

Dentition: Two distinct rows of extremely closely set, elongate and recurved conical teeth present in both upper and lower jaws. Upper jaw teeth somewhat larger and more recurved than those of lower jaw. Lips fleshy, and teeth embedded.

Squamation: Body scales cycloid. Head and opercular region asquamate. Chest fully scaled, except along ventral midline. Scales conspicuous. Squamation extends anteriorly, ventral to opercle, to approximately anterior margin of chest. Lateral line arched and complete, located well dorsal to lateral midline. Pored scales in lateral line highly embedded and difficult to visualize and count. Pores well developed. All fins asquamate, except for caudal fin, which bears several rows of cycloid scales of reduced size, particularly centrally on fin.

PIGMENTATION IN PRESERVATIVE: Body ground coloration olive to light brown above lateral midline, and silvery, guanine covered below midline (fig. 1). Pigmentation pattern above lateral midline characteristically blotchy and mottled, comprised of darker brown roundish blotches and broad lines over olive to light brown background. Blotches variable in size and somewhat closely arranged, particularly rostrodorsally. Body just ventral to lateral midline peppered with melanophores. Opercle, interopercle, and lacrimal iridescent silvery with golden hue. Preopercle, subopercle, and cheek iridescent and silvery. Short, composite, midlateral stripe present, comprised of three oblong dark gray translucent windows studded with chromatophores, and appearing much darker than surrounding region due to concentration of melanophores. Stripe located at midflank, beginning about level of terminal adducted pelvic-fin rays. Lips grayish. Lower jaw and gular region grayish. Snout with large black patch above upper lip. Two distinct black blotches present anterior to orbit; dorsal blotch covering anterior portion of postnasal spines on lateral ethmoid. Dorsal and ventral margins of orbit lined in black pigment. Interorbital region and nape grayish anteriorly to grayish-brown posteriorly. Large, oblong dark brown marking posterior to orbit and dorsal to opercle. Chest and belly silvery; silvery along ventral midline. Dorsal and anal fins hyaline to pale yellowish-white, with a slight concentration of black pigment distally on dorsal-fin spines. Base of dorsal fin black; becoming more prominent (i.e., darker) posteriorly. Pectoral and pelvic fins yellowish tan. Caudal peduncle pale tannish yellow with blackish saddle on dorsal margin. Base of caudal fin pale yellow. Caudal fin yellowish to olive proximal to base, becoming translucent to white distally. Membrane of caudal fin with concentration of black pigment, creating series of thin, black radiating lines, particularly near base.

LIGHT-ORGAN SYSTEM (LOS): In Photolateralis the light-organ system is internally characterized by a moderately enlarged, donut-shaped, and conspicuously spotted light organ in males that extends only slightly posteriorly into the gas bladder. In contrast, in members of Equulites , its sister taxon, the dorsolateral lobes of the light organ in males are greatly enlarged, heavily pigmented, and extend posteriorly well into the gas bladder. Internally, male members of Photolateralis exhibit posterolateral clearing of the silvery gas bladder lining, corresponding in extent to the external translucent lateral stripe or windows on the flank. The light-organ system in the new species is similar to that described for males of other members of Photolateralis (see Sparks, 2006; Sparks and Chakrabarty, 2015). In the new species, lateral clearing of the gas bladder lining corresponds to the three external translucent midlateral windows, the anteriormost window located at about the midpoint of the adducted pectoral-fin rays. Externally, members of Photolateralis are distinguished from all other leiognathids by the presence of a translucent flank stripe, which, depending on the species, may be comprised of either multiple independent translucent windows ( P. stercorarius , P. moretoniensis , and the new species) (figs. 1, 3A–C), or a continuous midlateral band ( P. antongil ) (fig. 3D). In Photolateralis , the translucent lateral stripe is either lacking entirely in females, or is considerably less well developed.

DISTRIBUTION: Known only from a single specimen acquired at a fish market ( 23° 36′ N; 058° 33′ E) in northeastern Oman, Sultanate of Oman. The   GoogleMaps new species is presumably more widespread in the region as well as in the Gulf   GoogleMaps of Oman. Extensive   GoogleMaps recent surveying and collecting in the adjacent portion of the Persian (Arabian) Gulf did not result in any additional observations of this species (personal obs.).

ETYMOLOGY:Named in reference to the characteristic translucent midlateral windows, which are rounded and appearing spotlike. The specific epithet, polyfenestrus , is used as an adjective.