Squatina argentina Marini 1930
Creators: name: Vaz, Diego F. B.
name: De, Marcelo R.
Publisher: name: Zenodo
Year: 2013
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Elasmobranchii
Squatiniformes
Squatinidae
Squatina
Squatina argentina

description: Squatina argentina (Marini, 1930)
(Figs. 24–30; Tabs. 5–6)
Rhina argentina Marini, 1930: 5 –7, fig. 1 (original description, Western South Atlantic, near shore, province of Buenos Aires, Argentina).
Squatina argentina: Marini, 1936: 19 –30, fig. 3 (taxonomic revision); Roux, 1977: 159–168, fig. 8 (in part, only MNHN 1984.33, taxonomic revision); Roux, 1979: 124–125, fig. 10 (in part, only MNHN 1984.33; taxonomic account); Solé- Cava and Levy, 1987: 139–144 (isozimic studies, cited as "morphotype III"); Vooren and da Silva, 1991: 589–602, fig. 6 (taxonomic revision); Gadig et al., 1999: 133–136 (taxonomic account); Milessi et al., 2001: 1–7, fig. 2b (taxonomic account); Soto, 2001: 96 (listed); Gadig and Gomes, 2003: 27 (listed); Soto and Mincarone, 2004: 83 (listed); Bernardes et al., 2005: 72 (taxonomic account); Compagno et al., 2005: 138–139, pl. 17 (identification guide); Vooren and Klippel, 2005: 57–82, fig. 4.1c (ecology); Carvalho et al., 2012: 171–183, figs. 2b, 3b, 4b, 6b (description of neurocranium).
Squatina squatina:?Schreiner and Miranda Ribeiro, 1903: 80 (taxonomic account);?Miranda Ribeiro, 1907: 169–171, fig. 10 (taxonomic account, figured).
Holotype. MACN 574, juvenile male (455 mm TL), Quequén, Province of Buenos Aires, Argentina (not examined).
Additional material examined. 8 specimens (see Appendix 1).
Diagnosis. A species of Squatina distinguished from congeners by a darker background color, ranging from dark-brown to reddish-brown (vs. light-brown to dark-brown in S. guggenheim and S. occulta), higher number of tooth rows with 24 vertical tooth rows in both upper and lower jaws (tooth formula 12-12/12-12; vs. 9-9 to 10-10 / 9-9 to 11- 11 in S. occulta, and 9-9 to 11-11 / 9-9 to 11- 11 in S. guggenheim), and anterior half of pectoral fin margin convex (vs. anterior margin of pectoral fin straight). Squatina argentina is further distinguished from S. guggenheim and S. occulta by interspiracular surface covered by small and homogeneous dorsal denticles, without enlarged denticles (vs. a pair of enlarged, conical and morphologically distinct dermal denticles between spiracles in S. occulta and S. guggenheim). Squatina argentina is also distinguished from S. occulta by lacking blackish irregular small spots surrounding white spots on dorsal surface (i.e. absence of ocelli-like markings). Squatina argentina is further distinguished from S. guggenheim by having dorsal midline denticles on trunk morphologically similar to other trunk denticles and barely organized in a row (vs. in S. guggenheim, dorsal midline row of enlarged denticles morphologically distinct from other trunk denticles), denticles close to origin of pectoral fin morphologically homogeneous, similar to other pectoral denticles (vs. presence of a pair, or more, enlarged and morphologically distinct denticles from other pectoral denticles, in S. guggenheim). Squatina argentina is further distinguished from Squatina sp. by lower number of vertebral centra (maximum values 136 vs. 150, respectively).
Description. Measurements in Table 5, meristic data in Table 6. The following description is based on all specimens. For the description below, refer to Figs. 24–30.
External morphology. Body robust, elongate and dorsoventrally depressed from head to origin of caudal fin (head height 5.2 to 7.4% TL). Abdominal region longer than wide, not tapering abruptly near origin of pectoral and pelvic fins; pectoral-pelvic distance 9.9 to 11.7% TL; width at pectoral origins 13.7 to 15.7% TL, and trunk width 15.9 to 18.4% TL. Head broad, anterior margin rounded, and posterior margin concave (Fig. 25). Dermal folds extend along entire lateral margin of head, from distal end of ventral labial furrow to superior margin of first gill opening. Dermal fold margins straight to slightly convex in some specimens, without lobes or projections (Fig. 53 c). Snout very short; anterior margin between nostrils straight to slightly convex, with dorsal surface straight. Preorbital length 2 to 3.7% TL, without preorbital pit. Eyes small, not greatly protruding above head, and slightly obliquely positioned, with posterior margin external to anterior margin (preorbital distance 4.4 to 5.9% TL; eyelength 2.3 to 2.9% TL and width 1.3 to 1.9% TL). Eyes widely separated, interorbital surface slightly bulging; interorbital distance 8.8 to 10% TL. Spiracles well separated from eyes (eye-spiracle distance 2.4 to 3.3% TL), wider than long, about equal or slightly larger than eyes (spiracle length 2.4 to 3.1% TL), comma shaped, with a knob on inner half of posterior margin. Interspiracular distance about equal or slightly smaller than interorbital length; interspiracular surface straight. Pseudobranchial folds on anterior margin of spiracle generally more than ten (variable depending on preservation).
Nostrils small, terminal on head, approximately one-half length of eye, greatly spaced apart (6.7 to 7.1% TL), and positioned just dorsal to mouth upper lip. Anterior nasal flap very large, overlapping mouth, with three very developed, ventrally directed barbels; inner and outer barbels elongate and spatulate, larger than nasal aperture; outer barbel slightly wider than inner barbel; median barbel somewhat rectangular, wider than long, with fringed free margin, its length about half that of outer barbel. Posterior nasal flap slightly fringed, confluent with lateral dermal fold, less developed than anterior nasal flap, and protruding only slightly from nasal margin. Mouth large, terminal on head, posteriorly arched, and extending to about mid-length of eye (mouth width 13.7 to 15.4% TL). Upper labial furrow very large, conjoined, forming a deep preoral groove from symphysis to posterior jaw angle; lower labial furrow smaller than upper furrow, length about one-fourth of mouth width. Lower labial furrow extends from posterior mid-length of lower labial cartilage to posterior to jaw angle. No teeth externally visible with mouth closed. Gill openings covered laterally by pectoral fins, but inner edges of slits visible ventrally. Distance between first and fifth branchial apertures very short (intergill length 2.1 to 3% TL). Gill slits widely separated, width between first gill openings 8.2 to 9.8% TL; distance between opposite gill slits very similar.
Pectoral fins very large, approximately two times longer than wide (length 32.4 to 36.7% TL and width 16.5 to 18.9% TL), with anterior angular projection slender, with acute apex. Anterior pectoral margins with a prominent convexity (‘shoulder’) on anterior half of pectoral fin (specimen MNHN 1984.33 with almost straight anterior margin of pectoral fin; Figs. 27 a, b). Posterior pectoral margin slightly concave. Inner margin strongly convex, its length slightly longer than pectoral fin width (pectoral fin inner margin 17.1 to 19.8%, mean 18.2% TL; pectoral fin width 16.5 to 18.9%, mean 17.8% TL; one specimen, UERJ 975, with pectoral inner margin slightly smaller than width). Pectoral-fin base length large (10.5 to 13.4% TL), positioned anteriorly on body (pre-pectoral length 19.2 to 21% TL). Pelvic fins elongate, triangular to semi-rhomboidal, much longer than wide (length 22.1 to 23.6% TL and width 13.0 to 14.2% TL). Anterior, posterior and inner margins straight to slightly convex, with free rear tip bluntly rounded, not reaching origin of first dorsal fin. Pelvic fin broad at more or less its midwidth, slender at margins. Distal ends of pectoral fins reaching anterior margins of pelvics.
Tail elongate, slightly longer than length of head and trunk (cloaca-caudal length 49.2 to 51.8% TL; mean 50.6% TL). Tail slightly depressed, its width 9.2 to 11.7% TL and height 4.5 to 5.7% TL. Caudal peduncle strongly depressed, short, without precaudal pit or lateral keels. Dorsal fins similar in size and shape, positioned on tail posterior to pelvic fin free rear tip; first dorsal origin close to tail midlength. First dorsal fin just taller than second (means: first dorsal fin base length 3.8% TL, height 5.2% TL; second dorsal fin base length 3.3% TL and height 4.6% TL). Anterior margins of dorsals straight to slightly convex, bent posteriorly; both inner and outer apices narrowly rounded (Fig. 25 e). Posterior margins straight to slightly convex, generally upright, with posterior inner margin straight. Caudal fin hypocercal, proportionally short, upper margin straight to slightly convex (10.8 to 11.8% TL), lower margin convex and larger than upper (14 to 16.3% TL), and caudal fin height 10.6 to 14.9% TL. Posterior caudal margin with a prominent notch at midheight, and convex on both upper and lower posterior margins (Fig. 25 f).
Coloration. Dorsal color in preservative with dark brown to reddish-brown background, with several whitish, small and rounded spots symmetrically positioned on entire dorsal surface. Size of spots variable; larger whitish spots one-half to equal to eye length, occurring mainly on pectoral and pelvic fins. Small spots rounded, slightly greater than one-half eye length, occurring on entire dorsal surface and densely grouped on trunk. Several small spots, usually more than five, surrounding some larger spots on pectoral fin, forming rosette-like markings. Pectoral fin with larger spots, about eye length in size, forming specific pattern: at level of pectoral origin, one spot positioned medially (close to pectoral origin), another positioned laterally (close to pectoral margins), one on pectoral center level with pectoral base midlength, one near pectoral insertion, and one centrally at pectoral inner margin (Fig. 25 d).
Ventral coloration uniform creamy-white on smaller specimens, and dark beige in large specimen (UERJ 975) on central region of head, external and inner margins of pectoral fins, posterior region of trunk, and origin of pelvic fins. Tail dark beige from close to tail origin to origin of lower caudal fin lobe; tail posteriorly with dark to reddishbrown color similar to dorsal surface. Remainder of ventral surface creamy-white to beige.
Dentition. Small gradient monognathic heterodonty; teeth with little morphological variation. Upper jaw teeth proportionally smaller than lower jaw teeth, and slightly more spaced apart. On upper jaw, teeth of first three vertical medial rows and both distal vertical rows slightly smaller than teeth of central vertical rows. On lower jaw, teeth of first and second vertical inner rows with root less wide than other teeth; teeth on distalmost four vertical rows proportionally smaller than others.
Teeth in 24 rows in both upper and lower jaw (tooth formula 12-12/12-12; a neonate, MZUSP 73170, with only 10 rows on right lower jaw). Tooth row arrangement without overlap, with a longitudinal row independent from others, with slight differences between upper and lower jaws. Innermost three vertical rows on each palatoquadrate densely grouped at symphysial region, with fourth longitudinal row separated posteriorly from anterior rows. Fifth to last upper vertical rows greatly spaced apart from fourth row. Distalmost two rows positioned more posteriorly than distal rows in S. occulta, S. guggenheim and Squatina sp. Tooth rows equally spaced throughout Meckel’s cartilage, and without teeth adjacent to symphysis, as in upper jaw. Tooth morphology with bulky main cusp, upright and bent lingually, without serrations or accessory cusplets (Fig. 29). Fracture zone on mid-height of main cusp of upper teeth (e.g. MOFURG 457). Tooth crown base laterally expanded, with prominent heels, projected diagonally in most teeth (projecting laterally to slightly diagonally on teeth of first upper row). Cutting edges of main cusp and lateral heels sharp, prominent and continuous. Labial face of tooth crown convex. Crown base with a prominent rounded apron, labially overhanging root but not reaching root base. Lingual crown face convex, contiguous with short, slender and cylindrical uvula covering dorsal surface of root lingual protuberance. Crown base without evident striae near junction with root. Mediolingual foramen present on distal end of lingual protuberance; at least four marginolingual foramina present. Sexual dimorphism in teeth not discernible.
Dermal denticles. Dermal denticles densely covering entire dorsal surface, with exception of posterior margins of unpaired fins and anterior apex of pectoral fin. Midwidth of trunk and tail with dermal denticles usually larger than those on head, lateral region of trunk and tail, and pectoral and pelvic fins. Dermal denticles with posteriorly directed crowns, with four ridges over anterior surface extending from crown base to apex. Central fifth ridge not observed in any denticle (as in S. occulta and S. guggenheim). Some denticles on surface of pectoral fin with only three ridges (one central and two lateral ridges). Basal plate morphology slightly variable. Trunk and tail with rounded basal plate, but rhomboidal on pectoral fin (Figs. 30 d–f). In some juveniles, an indistinct midline row of slightly enlarged dermal denticles present, usually from origin of tail to origin of first dorsal fin. Morphology of enlarged midline denticles similar to others on dorsal surface, with an enlarged basal plate (1.5 times diameter of basal plate of other dorsal denticles; pattern similar to S. occulta).
Enlarged denticles on head symmetrically organized, with two rows with two to three denticles each between nostrils, from anterior margin of snout to anterior margin of eye (directly over lateral margins of anterior fontanelle of neurocranium). Two enlarged denticles obliquely positioned anterior to each eye, with anteriormost reaching anterior margin of snout (over posterolateral margins of preorbital processes). A pair of denticles present posterior to each eye, on postorbital process. Enlarged denticles absent from interspiracular region (differently from S. occulta and S. guggenheim). Enlarged denticles on head distinct, with rounded basal plate, three to four times diameter of basal plate of other dorsal denticles. Enlarged denticles with large, conical and posteriorly directed crown, with smooth base; crown midheight with ten ridges, and crown apex acute and smooth (similar as described for S. occulta and S. guggenheim). Sexual dimorphism in morphology and distribution of dermal denticles absent.
Remarks. This species is uncommon in Brazilian zoological collections, accounting for the low number of specimens examined. The diagnostic characters described for S. argentina were not found in any specimen of the other species, however. Diagnostic characters such as tooth count, shape of pectoral fin and coloration were already cited by previous authors, including in the original description (Marini, 1930, 1936; Vooren and da Silva, 1991; Compagno et al., 2005).
In comparison to S. occulta and S. guggenheim (Figs. 9, 21), the dermal denticle crown of S. argentina is similarly elongate and more narrow, with crown ridges more closely positioned to each other; however, due to the small sample studied, it was not possible to confirm if this is a diagnostic character for S. argentina. Due to the low number of specimens available, it was also not possible to describe and compare the morphology of visceral arch elements, vertebral column, and paired and unpaired fins. Radiographs show an apparently similar morphology of these elements to those described above for S. occulta and S. guggenheim (see below). The only difference observed was the general outline of the basihyal, as the anterior segment does not project as far rostrally as in S. occulta, and is similar to that described for S. guggenheim; however, a prepared skeleton is necessary for confirmation.
The female reproductive system could not be examined and no adult male was available for study; reproductive features in this species were studied by Vooren and da Silva (1991) and Vooren and Klippel (2005). The larger specimen (UERJ 975, 646 mm TL; Figs. 24, 25) has an incomplete clasper, with a short clasper groove beginning close to pelvic fin insertion. In juveniles, clasper length varies between 10.7 and 10.8% TL (inner length), 1.7 to 2.6% TL (outer length) and width from 0.8 to 1% TL. We also could not examine embryos and determine size of birth in S. argentina; however, the smallest specimen examined (MZUSP 73170, a 280 mm TL female; Fig. 28) lacks a yolk-sac, and the embryonic yolk-connection is completely closed by hypaxial musculature. A small scar is still visible though, indicating that it must have closed recently; size at birth may therefore be slightly less than 280 mm TL.
Geographic distribution. According to material examined, Squatina argentina is distributed from Santa Catarina state in Brazil to southern Uruguay. The type-locality, however, is off northern Argentina (39o S, 56o W; Fig.40) (also Gomes et al., 2010). Vooren and Klippel (2005) proposed that this species occurs off Rio de Janeiro state; however, this was not confirmed.
description: Published as part of Vaz, Diego F. B. & De, Marcelo R., 2013, Morphological and taxonomic revision of species of Squatina from the Southwestern Atlantic Ocean (Chondrichthyes: Squatiniformes: Squatinidae), pp. 1-81 in Zootaxa 3695 (1) on pages 34-45, DOI: 10.11646/zootaxa.3695.1.1, http://zenodo.org/record/284327