Squalus albicaudus De, De & Gomes, 2016, sp. nov.

Squalus albicaudus sp. nov. (Figs. 42–50; Tables 3, 10– 11) Suggested common names: Brazilian whitetail dogfish; Cação-bagre-de-cauda-branca (Portuguese). Squalus megalops (not Macleay): Regan, 1908: 45, 47 (identification key, listed; global); Bigelow & Schroeder, 1948: 454 (cited); Bigelow & Schroeder, 1957: 29, 36, 37, figs. 3 C, 4 (revision; Northwestern Atlantic); Bass et al., 1976: 11 –13, 16– 18, figs. 6 B, 7 B, 8 (C, D), 11, pl. 3 (revision; Eastern South Africa); Cadenat & Blache, 1981: 51, 52 (revision; Mediterranean Sea); Compagno, 1984: 118, 119 (revision; global); Muñoz-Chápuli, 1985: 397, 398, fig. 1 (cited); Muñoz- Chápuli & Ramos, 1989: 1–21, figs. 1, 2 (E, F), 3 (D, E) (revision; Eastern Atlantic); Calderón, 1994: 1–104, fig. 5 A (cited); Nion et al., 2002: 4 (listed); Haimovici et al., 2003: 38, 39 (cited); Meneses & Paesch, 2003: 8, 25, 45 (cited); Bernades et al., 2005: 49, 70 (cited); Compagno et al., 2005: 74 (description; global); Hazin et al., 2006 (cited); Jablonski et al., 2006: 110, 177, 178 (cited); Louro & Rossi-Wongtschowski, 2007: 18, 27–30, 49, figs. 15, 16 (cited); Carrier et al., 2010: 44 (cited); Viana, 2011: 92–129, figs. 35–56 (revision; Brazil); Rosa & Gadig, 2014: 92 (listed; Brazil). Squalus cubensis (not Howell-Rivero): Figueiredo, 1977 (in part): 8 (description; Southern Brazil); Lucena & Lucena, 1981: 4 (listed; Brazil); Myagkov & Kondyurin, 1986: 1–20, fig. 1 (A, E, F, H) (revision; Atlantic); Lessa et al., 1999: 14, 61, 150 (cited, listed; Northeast Brazil); Compagno, 2002: 384 (description; Northern and Southern Brazil, Argentina, Uruguay); Compagno et al., 2005: 75, pl. 3 (description; Southwest Atlantic Ocean); Last et al., 2007: 21–22, figs. 10 A, 11 A (cited; Southeast Brazil); Nunan & Senna, 2007: 169, 170 (in part) (cited; Brazil); Viana, 2011 (in part): 130–162, figs. 57–77 (revision; Brazil). Squalus sp. of the megalops-acutipinnis-cubensis group Cadenat & Blache, 1981: 51, 52, fig. 31 (F, G) (revision; Mediterranean Sea); Figueiredo, 1981: 17 (listed; Brazil). Squalus sp. of the megalops group: Marques, 1994 (cited; Brazil); Gomes et al., 1997: 95, 98– 109 (description; Brazil); Marques, 1999 (cited; Brazil). Squalus sp.: Gomes et al., 1997: 98 (listed; Brazil); Tomás et al., 2010 (cited; Southeast Brazil). Squalus of the megalops / cubensis group: Gadig, 2001: 29, 36, 54, 58– 60 (listed; Brazil). Squalus sp. A: Soto, 2001: 95, 96 (listed; Brazil); Soto & Mincarone, 2004: 74 –79 (listed; Brazil). Squalus sp. 2: Gomes et al. 2010: 44 –46 (cited; Brazil). Holotype. MNRJ 30188, adult male, 525 mm TL, north coast of Espírito Santo state, Brazil, 19 ° 42 ' 54 "S, 39 ° 25 ' 57 "W, 195 m. Collected on 30 June 2000, Station 0 531, Thalassa cruise, Revizee program. Paratypes (11 specimens). MNRJ 30173, adult female, 590 mm TL, south coast of Bahia state, between Itacaré and Ilhéus, Brazil, 14 ° 28 ' 58 "S, 38 ° 54 '0"W, 278 m; MNRJ 30174, adult female, 580 mm TL, south coast of Bahia state, between Itacaré and Ilhéus, Brazil, 14 ° 28 ' 58 "S, 3 8 ° 54 '0"W, 278 m; MNRJ 30175, adult female, 560 mm TL, south coast of Bahia state, between Itacaré and Ilhéus, Brazil, 14 ° 28 ' 58 "S, 38 ° 54 '0"W, 278 m; MNRJ 30176, adult female, 540 mm TL, south coast of Bahia state, between Itacaré and Ilhéus, Brazil, 14 ° 28 ' 58 "S, 38 ° 54 '0"W, 278 m; MNRJ 30177, adult male, 450 mm TL, Morro de São Paulo, Bahia, Brazil, 13 ° 21 ' 51 "S, 38 ° 40 ' 49 "W, 421 m; MNRJ 30181, adult male, 482 mm TL, Canavieiras, Bahia, Brazil, 15 ° 42 ' 41 "S, 38 ° 37 ' 18 "W, 251 m; MNRJ 30183, juvenile female, 425 mm TL, Salvador, Bahia, Brazil, 13 ° 8 ' 54 "S, 38 ° 28 ' 41 "W, 334 m; MNRJ 30184, adult male, 480 mm TL, Salvador, Bahia, Brazil, 13 ° 8 ' 54 "S, 38 ° 28 ' 41 "W, 334 m; MNRJ 30185, adult male, 440 mm TL, Salvador, Bahia, Brazil, 13 ° 8 ' 54 "S, 38 ° 28 ' 41 "W, 334 m; MNRJ 30186, adult female, 590 mm TL, north coast of Espírito Santo state, Brazil, 19 ° 42 ' 54 "S, 39 ° 25 ' 54 "W, 202 m; MNRJ 30187, adult female, 610 mm TL, north coast of Espírito Santo state, Brazil, 19 ° 42 ' 54 "S, 39 ° 25 ' 57 "W, 195 m. Non-type material (9 specimens). MZUFBA uncatalogued, juvenile female, 420 mm TL, adult male, 502 mm TL, Praia do Forte, Mata de São João, Bahia, Brazil; NUPEC 96, adult male, 460 mm TL, South of Barra de Santos, São Paulo, Brazil; NUPEC 1354, neonate female, 285 mm TL, juvenile female, 355 mm TL, Ilha Vitória, São Paulo, Brazil; TAMAR 10.38, adult male, 490 mm TL, locality same as MZUFBA; TAMAR 10.39, juvenile female, 459 mm TL, locality same as MZUFBA; TAMAR 10.41, juvenile female, 445 mm TL, locality same as MZUFBA; TAMAR 10.42, juvenile female, 410 mm TL, locality same as MZUFBA. Diagnosis. Squalus albicaudus sp. nov. can be distinguished from its congeners by the following combination of characters: caudal fin with a mostly white ventral caudal lobe, dorsal caudal margin white at midline, and postventral caudal margins broadly white; pectoral-fin posterior margin broadly white; first dorsal fin with anterior margin also conspicuously white on its anterior half. Squalus albicaudus sp. nov. differs from all species of the S. mitsukurii group by: snout short vs. snout large; pectoral-fin free rear tips pointed vs. pectoral-fin free rear tips rounded; dermal denticles lanceolate and unicuspid vs. dermal denticles rhomboid and tricuspid. Squalus albicaudus sp. nov. is clearly distinct from S. cubensis by: snout strongly pointed (vs. snout somewhat rounded); second dorsal-fin spine not reaching second dorsal-fin apex (vs. spine reaching second dorsal-fin apex); first dorsal fin with dark apex, but not as a black blotch (vs. conspicuous black blotch on both dorsal fins); pectoral fins with posterior margin broadly white (vs. narrowly white). These two species also differ in external morphometrics such as: shorter first dorsal fin (anterior margin length 10.9 %, 9.7 %– 11.2 % TL vs. 11.6 %, 11.6 %– 12.7 % TL in S. cubensis); shorter second dorsal fin (anterior margin length 9.2 %, 8.8 %– 10.8 % TL vs. 12.3 %, 11.2 %– 11.6 % TL in S. cubensis; inner margin length 5.0%, 4.1 %– 5.2 % TL vs. 5.6 %, 5.5 %–6.0% TL in S. cubensis); more slender second dorsal-fin spine (width at base 0.9 %, 0.6 %– 0.9 % TL vs. 1.0%, 1.0%– 1.2 % TL in S. cubensis); and clasper much more elongated in (inner margin length 7.1 %, 6.9 %– 7.7 % TL vs. 8.0%, 3.3 %– 3.8 % TL in S. cubensis). Description. External morphology. Measurements and counts are summarized in Tables 10–11. Body fusiform and thin throughout, slightly arched dorsally, equally deep from head to trunk (head height 1.0, 0.8 –1.0 times trunk height and abdomen height), and broader at head than at trunk (head width 1.2, 1.0– 1.4 times trunk height, and 1.4, 1.2–1.4 times abdomen height). Head very short and narrow (length 21.8 %, 18.7 %– 24.7 % TL; its greatest width at mouth (11.1 %, 10.9 %–12.0% TL). Snout pointed at tip, conspicuously short (length 7.1 %, 6.8 %– 7.8 % TL); anterior margin of nostrils bifurcate and wide, equally near snout tip and mouth; prenarial length 1.0, 0.8 –1.0 times distance from nostrils to upper labial furrow, and 0.5, 0.4–0.5 times preoral length; internarial space 1.1, 0.8 –1.0 times eye length. Eyes oval and markedly large (length 4.0%, 4.2 %– 5.3 % TL, and 1.5, 1.8–2.1 times their height); anterior margin of eyes convex and posterior margin notched; interorbital space 8.4 %, 8.2 %– 8.9 % TL. Prespiracular length 12.5 %, 11.7 %– 13.8 % TL, and 0.5 (0.6–0.7) times prepectoral length and 1.7 (1.7–1.9) times preorbital length. Spiracles crescent-shaped and wide, their length 1.5 % (1.3 %–2.0% TL), and 0.4, 0.3–0.4 times eye length. Prebranchial length 1.5 (1.3–1.5) times prespiracular length. Gill slits vertical and low, with fifth gill slit 1.1 (1.0– 1.4) higher than first gill slit. Preoral length 9.8 %, 9.2 %– 11.2 % TL and equal to 1.2, 1.3–1.5 times mouth width. Mouth arched and strongly broad, its width 1.5, 1.5–1.8 times prenarial length and 1.9, 1.9 –2.0 times internarial space; upper labial furrow with thin fold, very large (length 2.3 %, 2.1 %– 2.5 % TL); lower labial furrow also large, although without a fold. Teeth unicuspid and similar in both jaws, wide and flattened labial-lingually at crown, imbricate laterally; upper teeth much smaller than lower teeth; cusp oblique, somewhat elongate and heavy, directed laterally; mesial heel slightly notched; distal heel rounded; mesial cutting edge somewhat straight; apron thick and rather elongate. Three series of teeth in upper jaw and two series of teeth in lower jaw in holotype (paratypes 2–3 series in both jaws); tooth rows ranging from 12 – 12 (13–14 paratypes) in upper jaw and 11 – 11 (11–12 paratypes) in lower jaw (Fig. 43). Pre-first dorsal fin length 1.1 (1.2–1.8) times prepectoral length. Origin of first dorsal fin anterior to pectoral free rear tips. First dorsal fin with anterior margin markedly convex and posterior margin straight, although concave anteriorly; first dorsal-fin apex rather rounded; first dorsal-fin free rear tip rounded (Fig. 44); first dorsal-fin inner margin very short, its length 5.6 % (4.9 %– 6.1 % TL); first dorsal fin short (length 1.7, 1.6 –2.0 times its height) and low (height 7.9 %, 6.8 %–8.0% TL and 1.4, 1.2–1.6 times first dorsal-fin inner margin length, and 1.1, 0.9–1.1 times preorbital length). First dorsal-fin spine slender, thick (its base width 1.0%, 0.7 %– 1.1 % TL) and elongate (its length 4.2 %, 2.3 %– 4.1 % TL), reaching one-half of first dorsal-fin height (0.3–0.5 times first dorsal-fin height in paratypes). First dorsal-fin length 1.3 (1.0– 1.3) times larger than second dorsal-fin length. Interdorsal space 1.1 (1.0– 1.3) times prepectoral length and 2.2 (1.7–2.6) times dorsal-caudal space. Pre-second dorsal length 2.8, 2.5– 3.1 times prepectoral length and 3.2, 2.8–3.3 times dorsal-caudal margin length. Second dorsal fin also short (length 2.0, 1.9–2.3 times its height) and somewhat tall (height 5.4 %, 4.9 %– 6.2 % TL, and 1.1, 0.9–1.3 times second dorsal-fin inner margin length); first dorsal-fin anterior margin convex and posterior margin markedly concave; first dorsal-fin apex rounded and pointed at free rear tip (Fig. 44); second dorsal-fin inner margin short, its length 5.0% (4.1 %– 5.2 % TL). Second dorsal-fin spine conspicuously thin and large, almost reaching second dorsal-fin height, its length 5.1 % (3.4 %–5.0% TL), and 0.9 (0.7–0.9) times second dorsal-fin height, and 1.2 (1.0– 1.8) times first dorsal-fin spine length. Pectoral fins small but also broad with anterior margin length 13.4 % (11.8 %– 14.4 % TL), 1.2 (1.2–1.4) times posterior margin length, and 1.5 (1.3–1.5) times inner margin length; pectoral-fin posterior margin 10.7 % (9.7 %– 11.8 % TL); pectoral-fin anterior margin straight, inner margin convex and posterior margin concave; pectoral-fin apex rounded and lobe-like (Fig. 42); pectoral-fin free rear tips markedly pointed, extending beyond horizontal line at pectoral apex; posterior margin length 1.1 (0.8 –1.0) times trunk height. Pectoral-pelvic space 0.7 (0.5–0.9) times pelvic-caudal space. Pelvic fins nearer first dorsal fin than second dorsal fin in holotype and young paratypes (or nearest second dorsal fin in adult paratypes). Pelvic-fin anterior margin convex and posterior margin straight; pelvic-fin apex rounded and narrow; pelvic-fin free rear tips rounded and lobe-like; pelvic fins elongate, their inner margin length 6.3 % (4.2 %– 6.3 % TL). Claspers cylindrical, thin, and flattened dorsoventrally; claspers short, slightly extending beyond pelvic-fin free rear tips, their inner length 7.1 % (6.9 %– 7.7 % TL) and 1.1 (1.2–1.4) times larger than pelvic-fin inner margin length; clasper groove longitudinal and small, located dorsally; apopyle narrow, placed in proximal end of clasper groove; hypopyle constricted at distal end of clasper groove; rhipidion narrow and short, blade-like and somewhat thick, positioned medially at distal end of clasper (Fig. 45). Caudal peduncle slender with soft caudal keel on each side; upper and lower caudal furrows markedly deep. Caudal fin slender and short, its dorsal caudal margin length 19.8 % (19.3 %– 21.2 % TL), and 0.9 (0.8–1.1) times head length and 1.7 (1.7–1.9) times preventral caudal margin; dorsal caudal margin straight, post-ventral caudal margin (upper and lower) convex (Fig. 46); posterior tip pointed; caudal fork between lobes with conspicuous concavity and very narrow (width 6.5 %, 6.2 %– 7.2 % TL); ventral tip rounded; preventral caudal margin also convex and short, its length 11.4 % (10.5 %– 11.9 % TL) and 1.8 (1.7–2.6) times pelvic-fin inner margin length. Dermal denticles (Fig. 47). Denticles unicuspid, lanceolate and markedly slender, their length much greater than width; dermal denticles moderately asymmetrical and near each other but not imbricate; median and lateral ridges prominent, bifurcate anteriorly; crown conspicuously expanded anteriorly and rather expanded laterally; cusp rounded and elongate posteriorly. Coloration (Fig. 42). Body brownish gray dorsally and white ventrally, gray laterally from between the pectoral and pelvic fins, turning whitish at caudal fin origin. First dorsal fin brownish, darker at fin web to apex; anterior margin broadly white on anterior half and dark brown at apex; posterior margin slightly white on anterior half and brown at apex; first dorsal-fin spine gray, darker anteriorly, white laterally and attip. Second dorsal fin brown throughout (few paratypes with white apex); second dorsal-fin posterior margin white; second dorsal-fin spine also gray, darker anteriorly and white at tip. Pectoral fins brown dorsally and ventrally (except at base) with posterior and inner margins conspicuously white, including apex and free rear tips. Pelvic fins light brown dorsally and white ventrally; pelvic posterior margin broadly white. Caudal fin mostly dark brown with dorsal caudal margin markedly white at midline; upper caudal blotch dark gray distally at dorsal caudal margin; post-ventral caudal margins conspicuously white, except for light gray caudal fork (caudal bar); posterior caudal tip also broadly white; preventral caudal margin dark gray anteriorly; ventral caudal lobe conspicuously white, including ventral caudal tip; caudal stripe blackish, thick and short. Skeletal morphology. Measurements and counts are summarized in Tables 3, 11. Neurocranium (Fig. 48). Neurocranium greatest width at level of postorbital processes (width 57.1 % CL) and narrower at interorbital region (28.8 % CL) and between opisthotic processes in the otic region (36.5 % CL). Rostrum spoon-like, comprised by precerebral fossa profound and short (its length 40.1 % CL), narrower proximal and distally than at its median portion; lateral rostral cartilages slightly cylindrical, flattened laterally; two lateral rostral appendices anteroventrally, hook-like; rostral prominence small, placed medially at tip of rostrum; rostral keel conspicuous and elongate, its length 25.0% CL, slightly transcending anterior margin of nasal capsules; prefrontal fontanelle constricted and rounded, anterior to brain at rostrum base. Nasal capsules rounded and markedly wide (width across nasal capsules 52.8 % CL), located lateral to rostrum; nasal apertures ventral; subnasal fossa oval and large, located at each side of rostral keel. Squa'us a'bicaudus sp. nov. Squa'us cubensis Measurements Paratypes Paratypes Gu 1 f οf Mexicο Caribbean Sea Hο 1 οtype Hο 1 οtype Cranial roof arched medially, strongly concave laterally at interorbital region, and elongate (postcerebral length 58.5 % CL); supraorbital crest with deep longitudinal sulcus, with a series of 10 foramina for the superficial ophthalmic branch of the trigeminal (V) and facial (VII) nerves; preorbital canal markedly broad, located anterior to a series of foramina for superficial ophthalmic branches (V, VII); canal for the ophthalmicus profundus nerve also clearly wide, placed just anterior to preorbital canal for the ophthalmicus nerve; preorbital processes inconspicuous laterally (width across preorbital processes 48.5 % CL); postorbital processes prominent, triangular and elongate (its length 10.2 % CL). Supraethmoidal processes conspicuous, cylindrical and paired, placed medioanteriorly in ethmoidal region; epiphyseal pit prominent and rounded, located posterior to supraethmoidal processes; ethmoideal region somewhat depressed ventrally with ectethmoid process wide, pointed and bifurcated distally; subethmoidean chamber constricted until anterior to basal angle; subethmoidal ridge slender and very elongate, almost reaching the basitrabecular process of basal plate; two small ethmoidal canals, located far anteriorly in the cranial roof at base of each nasal capsule. Otic region very narrow, comprised by a single and small otic capsule on each side; otic capsule delimited by anterior semicircular canal anteriorly, posterior semicircular canal posteriorly and sphenopterotic ridge laterally; lateral semicircular canal inconspicuous, located ventrally to sphenopterotic ridge; endolymphatic fossa rounded and shallow, placed between otic capsules; two small endolymphatic foramina, located anteriorly in fossa; two posterior perilymphatic foramina wide and rounded; otic crest slightly prominent mediodistally in the otic region; opisthotic processes somewhat pointed posterolaterally at each side of otic region (width across processes 36.5 % CL); hyomandibular facet shallow, placed lateroventrally and below lateral semicircular canal; lateral auditory groove profound, positioned anterior to hyomandibular facet; prootic process thick and conspicuous, located posterior to hyomandibular facet (width across hyomandibular facets 41.5 % CL). Orbital region with preorbital wall concave; orbitonasal canal ventral at preorbital wall; interorbital wall deep and large with optic foramen (II) broad, placed midventrally; trochlear foramen (IV) small, placed dorsally near supraorbital crest; eye-stalk prominent, located more posteriorly in interorbital wall and anterior to prooticum foramen; oculomotor foramen (III) and abducens foramen (VI) small, placed, respectively, dorsally and ventrally to eye-stalk; foramen prooticum for the trigeminal (V) and facial (VII) nerves markedly broad, positioned ventroposteriorly in interorbital wall; foramen for efferent of pseudobranchial artery very small, positioned over basal angle; transbasal canal also small, located anteriorly to foramen prooticum. Basal plate flattened and elongate (its length 38.6 % CL), narrower anteriorly at basitrabecular processes (width across processes 16.1 % CL) than posteriorly; basitrabecular process bean-shaped and prominent anteriorly; lateral prominence sinuous on each side of basal plate, posterior to basitrabecular processes; single cartilaginous process prominent laterally on each side, somewhat cylindrical (width across processes 30.3 % CL); foramen for carotid artery rounded and small, located anteromedially in basal plate; foramen for orbital artery small, located at base of each cartilaginous process. Occipital region with two triangular occipital condyles, placed ventrally; foramen magnum very wide (its width 9.2 % CL); foramen for vagus nerve (X) narrow; glossopharyngeal base markedly thick and subtriangular, placed posterolaterally on each side of occipital region, with foramen for glossopharyngeal nerve (IX) strongly broad and oval. Pelvic girdle and fin (Fig. 49). Puboischiadic bar transverse, short, slim, and thicker laterally, convex medially and concave more laterally at its anterior portion, posterior portion completely straight; lateral prepelvic process evident on each side, slightly rounded; two expansions lateroposteriorly articulating pubosichiadic bar to pelvic fin; two foramina at each side of puboischiadic bar. Basipterygium vertical, short and straight; anterior pelvic basal element subrectangular, elongate, its length corresponding to one-half length of basipterygium, and associated to three series of small irregular radials; pelvic radials elongate and slender, segmented into proximal and distal elements, the later shorter than the former; 13 total pelvic radials. Claspers (Fig. 49). Intermediate segment barrel-shaped and short, placed between the pelvic fin basipterygium and axial cartilage; beta cartilage rod-like, cylindrical, and large, its length corresponding to more than one-third length of dorsal terminal cartilage, located dorsally for attaching pelvic fin basipterygium to axial cartilage. Axial cartilage slender and somewhat sinuous with a deep groove evident lateroventrally; end-style very short, not reaching half length of dorsal terminal cartilage (or claw), located medially at end of axial cartilage; dorsal marginal cartilage inconspicuous, laterally over the axial cartilage; dorsal terminal cartilage (or claw) short, its length corresponding to one-third the axial cartilage length, slightly concave and pointed distally, connected anteriorly to dorsal marginal cartilage; dorsal terminal 2 cartilage leaf-like, very soft and small, attached anteriorly to dorsal marginal cartilage and medially to dorsal terminal cartilage (or claw), externally supporting the rhipidion. Ventral marginal cartilage conspicuous and thick, bowl-shape, broader posteriorly than anteriorly, with a prominent folded plate laterally; ventral terminal cartilage spatula-like, small, its length less than one-half of axial cartilage length, attached proximally to ventral marginal cartilage and axial cartilage; accessory terminal 3 cartilage (or spur) thick and short, its length corresponding to one-half axial cartilage length, inserted into folded plate of ventral marginal cartilage, s