A new species of Leposternon Wagler, 1824 (Squamata, Amphisbaenia) from northeastern Argentina Author Ribeiro, Siria Author Santos-Jr, Alfredo P. Author Zaher, Hussam text Zootaxa 2015 4034 2 309 324 journal article 10.11646/zootaxa.4034.2.4 69aeb7a8-4960-41a0-a9ed-cbe23aab24e0 1175-5326 242957 C09E1E16-5D8B-4F20-90A4-07050A1A560D Leposternon bagual sp. nov. ( Figs. 1–4 ) Leposternon microcephalum — Scrocchi & Giraudo (2005: 163, 181) Leposternon microcephalum ( partim )—Ribeiro et al . (2008: 35) Holotype . FML 11319 (field number REB 21242), an adult female from El Bagual Ecological Reserve ( 26º10’53’’S ; 58º56’39’’W ), Province of Formosa , Department of Laishi, Argentina , collected in 0 5 February 2002 , collector unknown ( Figs. 1 , 2 ). Paratypes . FML 11312 (field number REB 20887), a male collected in 0 1 October 1992 ; FML 11313 (field number REB 20888), a female collected in 14 June 1992 ; FML 11318 (field number REB 1227), a female collected in 0 1 February 1993 ; all three paratypes from El Bagual Ecological Reserve ( 26º10’53’’S ; 58º56’39’’W ), Province of Formosa , Department of Laishi, Argentina ; collector unknown. FIGURE 1. Leposternon bagual sp. nov. (holotype, FML 11319). (A) Dorsal, (B) lateral, (C) ventral view of the head; (D) pectoral and (E) cloacal regions. Scale bar = 5 mm. FIGURE 2. Leposternon bagual sp. nov. (holotype, FML 11319). (A) Dorsal, (B) lateral, (C) ventral view of the head; (D) pectoral and (E) cloacal regions. Scale bar = 5 mm. Diagnosis. Leposternon bagual sp. nov. is a medium-sized amphisbaenian (largest specimen total length 309.5 mm ) and can be characterized as a Leposternon and distinguished from all South American amphisbaenians by having the nostril openings on the ventral surface of snout, rostral and nasals fused into a single shield, gular portion without segmental cover and prefrontal bones in facial view with nasal process long and ‘T’ shaped (details of skull in Gans & Montero 2009 ) (Ribeiro et al. 2008). Additionally, the new species differs from all other South American amphisbaenians, except Leposternon spp. and Amphisbaena anomala ( Barbour, 1914 ) , in having the frontal portion of the head greatly depressed and pectoral shields irregular (not arranged in dermal regular annuli). It differs from the other species of the genus by the presence of rostral processes in the maxillae and nasals that contact each other in the facial portion of the skull ( Fig. 3 , Table 1). The new species further differs from L. cerradensis Ribeiro, Vaz-Silva & Santos-Jr, 2008 , L. infraorbitale ( Berthold, 1859 ) , L. microcephalum , L. octostegum ( Duméril, 1851 ) , L. scutigerum ( Hemprich, 1820 ) and L. wuchereri ( Peters, 1879 ) by the presence of 3 infralabial shields; and from L. cerradensis , L. kisteumacheri Porto, Soares & Caramaschi, 2000 , L. maximus Ribeiro, Nogueira, Cintra, Silva Jr. & Zaher, 2011 , and L. polystegum ( Duméril, 1851 ) by lacking precloacals pores. Leposternon bagual is further characterized by the following combination of pholidotic, meristic, cranial, and morphometric characters (see also Table 1 for a synthesis of diagnostic features within the genus): 1) two supralabials; 2) supraocular present; 3) 240–267 dorsal postpectoral half-annuli; 4) 206–214 ventral postpectoral half-annuli; 5) 11–12 tail annuli; 6) 27–29 dorsal segments in midbody half-annulus; 7) 23–27 ventral segments in midbody half-annulus; 8) 96 precloacal vertebrae; 9) many small and irregularly shaped pectoral shields ( Fig. 1 D); 10) adults specimens dark brown dorsally; 11) five premaxillary teeth; 12) four maxillary teeth; 13) six dentary teeth; 14) rostral process of nasal present; 15) rostral process of maxilla present; 16) premaxillary foramina present; 17) head length with 3.5–4.5% of snout-vent length; 18) rostronasal length with 22.6–23.5% of head length; 19) rostronasal width with 64.0–68.1% of the greatest width of head; 20) azygous length with 29.3–35.0% of head length; 21) azygous width representing 35.6–45.8% of the greatest width of head; 22) frontal suture length with 25.3–25.5% of head length; 23) parietal suture with 9.8–13.9% of head length; 24) temporal length with 18.9– 22.0% of head length; 25) temporal width with 13.2–17.8% of head width; 26) prefrontals length with 23.0–26.8% of head length; 27) prefrontals width with 38.3–41.7% of head width; 28) height posterior of head comprising 69.0–72.5% of head length; 30) comissure of the mouth length comprising 53.4–59.1% of head length; 29) midbody width with 3.2–4.4% of snout-vent length; and 30) tail length representing 4.9–5.6% of snout-vent length. Description of the holotype . The specimen is an adult female with 257 mm snout-vent length and 14.5 mm tail length (5.6% of total length); midbody diameter 9.2 mm ; tail diameter of five annuli 8.9 mm ; head length 9.0 mm (3.5% of snout-vent length); head anterior height 2.8 mm ; head posterior height 6.5 mm ; head anterior width 2.8 mm ; and head posterior width 6.8 mm ( Figs. 1 , 2 ). Dorsal portion of the head with four transversal row shields ( Figs. 1 A, 2A). Rostronasal 1.1 times wider than long and 0.1 times wider than its heigth, in contact with the first supralabials laterally, and azygous and prefrontals posteriorly. Nostrils opening in the ventral portion of rostronasal scutes. Prefrontals, azygous and supraoculars slightly fused ( Figs. 1 A, 2A). Prefrontals with irregular shape, slightly fused with azygous, almost as long ( 2.2 mm ) as wide ( 2.6 mm ), in contact with first supralabials laterally, and azygous and supraocular posteriorly. Azygous with anterior portion project ( Figs. 1 A, 2A) and posterior portion straight, 0.2 times longer than wide, in contact with the supraoculars laterally, and frontals posteriorly ( Figs. 1 A, 2A). Supraocular slightly quadrangular, 0.2 times wider than long, in contact with temporal posteriorly. Frontals paired (suture length 1.9 mm ), anterior portion projected and posterior portion straight, almost as long ( 2.28 mm ) as wide ( 2.31 mm ), in contact with temporals laterally and parietals posteriorly. Temporals slightly rectangular, 0.5 times longer than wide, disposed on each side of frontals ( Figs. 1 A, 2A), in contact with laterals parietals posteriorly. A pair of medial parietals (suture length 1.2 mm ) ( Figs. 1 A, 2A), roughly rectangular, 0.4 times wider than long, in contact with lateral parietals laterally and occipitals posteriorly. One small lateral parietal on each side of the pair of medial parietals, both with irregular shape, in contact with temporals anteriorly and body annuli posteriorly. A pair of occipitals, with irregular shape and size, in contact with the first row of dorsal anterior half-annuli posteriorly. Ocular slightly quadrangular, 0.3 times longer than high, in contact with first infralabial, anteriorly, and inferior portion of the second supralabial and postocular posteriorly. Two supralabials. First supralabial larger than second supralabial, 0.7 times longer than high, 1.9 times longer and 0.4 times higher than second supralabial, in contact with the second supralabials posteriorly. Second supralabial slightly rectangular, 0.2 times its width, higher than long, and in contact with three postlabials posteriorly ( Figs. 1 B, 2B). Three postlabials of reduced size, the smallest one located at the inferior portion of the second supralabial ( Figs. 1 B, 2B). FIGURE 3. Dorsal view of the skull in the genus Leposternon . (A) skull of Leposternon bagual sp. nov. (paratype, FML 11313) with rostral processes of the maxillae and nasals contacting each other on the facial portion of the skull; (B) skull of Leposternon aff. microcephalum (MRT 11984) with rostral processes of the maxillae and nasals not contacting each other on the facial portion of the skull; (C) skull of Leposternon polystegum (ZUFRJ 528) without rostral processes of the maxillae and nasals. Abbreviations: F, frontal; N, nasal; PF, prefrontal; MX, maxilla; NPPM, nasal process of premaxilla; RPM, rostral process of maxilla; RPPM, rostral process of premaxilla. FIGURE 4. Dorsal view of the heads of paratypes of Leposternon bagual sp. nov. (A) FML 11312, (B) FML 11313 and (C) FML 11318. Scale bar = 5 mm. Three infralabials, with the first one slightly triangular and in contact with the mental laterally and second infralabial posteriorly; the second one relatively narrow (3.3 times longer than the first infralabial), in contact with postmental and malars laterally and third infralabial posteriorly; the third one slightly rectangular, 0.2 times longer than first infralabial, in contact with postlabials and lateral malar laterally ( Figs. 1 C, 2C). Mental with posterior margin 0.55 times wider than anterior margin, in contact with postmental posteriorly. Postmental 0.4 times longer than wide, with anterior portion straight and posterior projected, in contact with malar and posterior malar intern laterally and genials posteriorly. Two small, irregularly shaped genials, disposed posteriorly to postmental. An elongated teardrop shaped malar, disposed on either sides of the post-mental, 1.4 times longer than wide, contacting posterior malars posteriorly. Two posterior malars located between the postmental and the lateral malar; the medial one in contact with the postmental and the outermost malar; and lateral one in contact with the lateral malar. Lateral malar 0.5 times longer than wide, tapering anterolaterally and rounded posteriorly, in contact with the postmalar row. Postmalar row formed by 10 small shields. Dorsal and ventral portions of the body divided by a lateral groove; dorsal region further divided by a vertebral groove; lateral grooves absent in the tail. Pectoral scales diamond-shaped, with central scales larger than lateral scales ( Figs. 1 D, 2D). Eighteen dorsal anterior half-annuli, 253 dorsal postpectoral half annuli plus two incomplete half-annuli, 214 ventral postpectoral half-annuli, five lateral half-annuli, and 12 tail annuli. Twenty eigth dorsal segments per half-annulus at midbody, 23 ventral segments per half-annulus at midbody, and 35 segments forming the fifth tail annulus. Anal flaps semicircular, 1.0 times longer than half-annuli, with 11 narrow segments ( Figs. 1 E, 2E). Ninety six precloacal vertebrae, with dorsal and ventral half-annuli around the body being more than twice the number of vertebrae. Color of holotype in preservative . Head, trunk and tail are uniform dark brown, except for the belly that is whitish. Variation . Variation on the meristic and morphometric characteristics of the paratypes is presented in Table 2 and in the Figure 4 . Additionally, the paratypes show some variation in the disposition and morphology of the cephalic shields in comparison to the holotype . FML 11312 has a poorly defined anterior border of the frontal; the posterior border of the left parietal is elongated, occupying the space where the occipital shield would be located on the right side. FML 11313 shows partially fused parietal and occipital shields. FML 11313 shows a pre-frontal portion with numerous diminute, irregularly shaped shields, a frontal portion with a rounded anterior border; and a tuberculate dorsal portion of the tail. Etymology . The specific epithet for the new species is used here as a noun in apposition, an allusion to the ecological reserve where the new species has been collected (El Bagual Reserve). The word bagual comes originally from the indigenous word cahual , which in Araucana culture (native inhabitants of Chile and Argentina ) is applied to cattle ( Di-Giacomo & Krapovickas 2005 ). Among other denominations, bagual is used by “Gauchos” to define a wild horse. TABLE 1. Pholidotic, cranial, and morphometric characters for the species of the genus Leposternon . Pholidosis : IL , Infralabial; PPO, precloacal pores; SL, Supralabial; DOA, Dorsal postpectoral halfannuli; VEA, Ventral postpectoral half-annuli; TA, Tail annuli; DS, Dorsal segments in midbody half-annulus; VS, Ventral segments in midbody half-annulus; PVE, Precloacal vertebrae; PEC, pectoral shields; COL, colorations specimens adults. Skull : PMXT, premaxillary teeth; MXT, maxillary teeth; DT, dentary teeth; RPN, rostral process of nasal; RPMX, rostral process of maxilla; FPMX, foramina of premaxilla. Morphometrics: HL/SVL, head length/snout-vent length expressed as a percentage; SSLL/HL, second supralabial length/head length expressed as a percentage (analyzed only in species with supralabials); RL/HL, rostronasal length/head length expressed as a percentage; RW/HW, rostronasal length/greatest width of head expressed as a percentage and analyze; RH/HH, rostronasal height/posterior height of head expressed as a percentage; AZL/HL, azygous length/head length expressed as a percentage; AZW/HW, azygous width/posterior height of head expressed as a percentage; AZL/FW, azygous length/azygous width expressed as a percentage; FSL/HL, frontal suture length/head length expressed as a percentage; PL/HL, parietal suture length/head length expressed as a percentage; TL/HL, temporal length/head length expressed as a percentage; TW/HW, temporal width/head head width expressed as a percentage; PFL/HL, prefrontal length/head length expressed as a percentage; PFW/HW, prefrontals width/head width expresses as a percentage; HH/HL, head posterior height/head length expressed as a percentage; CML/HL, commissure of the mouth length/head length expressed as a percentage; MB/SVL midbody width/snout-vent length expressed as a percentage; TL/SVL, tail length/snout-vent length expressed as a percentage; SD, standard deviation. Diagnostic characters are given in bold. Charact Species of Leposternon ers bagual cerradensis infraorbitale kisteumacheri maximus microcephalum octostegum polystegum scutigerum wuchereri 3/3 2/2 2/2 3/3 3/3 2/2 1/1 3/3 1/1 1-2/1-2 PPO Absent 2-4 Absent 2 2 Absent Absent 2-4 Absent Absent 2/2 2/2 3/3 2/2 2/2 2/2 1/1 3/3 2/2 1-2/1-2 SOC 1/1 Absent 1/1 0-1/0-1 1/1 1/1 Absent Absent Absent 1/1 DOA 240-267 299-341 250-292 244-271 404-448 204-255 353-398 253-363 259-295 231-263 (n = 4; Mean = (n = 6; Mean = (n = 20; Mean (n = 5; Mean = (n = 11; Mean (n = 119; Mean (n = 4; Mean = (n = 30; Mean (n = 5; Mean = (n = 5; Mean = 256; SD ± 13) 317.2; SD ± = 270,0; SD ± 256.2; SD ± = 424.9; SD ± = 228.1; SD ± 372.3; SD ± = 302.8; SD ± 270.2; SD ± 247.0; SD ± 16.4) 11.7) 11.0) 14.1) 7.6) 20.5) 31.0) 14.2) 14.4) VEA 206–214 302-333 229-285 246-259 408-448 192-229 342-390 252-349 250-278 226-254 (n = 4; Mean = (n = 6; Mean = (n = 20; Mean (n = 4; Mean = (n = 11; Mean (n = 120; Mean (n = 4; Mean = (n = 30 Mean = (n = 5; Mean = (n = 5; Mean = 211; SD ± 3) 319.3; SD ± = 250.4; SD ± 253.5; SD ± = 426.9; SD ± = 207.6; SD ± 363.8; SD ± 294.2; SD ± 261.6; SD ± 239.0; SD ± 17.9) 15.0) 5.4) 11.3) 11.1) 19.8) 27.3) 11.5) 11.0) 11-12 13- 15 9-13 12-14 14- 16 8-14 11 9- 18 12-14 11-13 (n = 4) (n = 6; Mean = (n = 20; Mean (n = 5; Mean = (n = 11; Mean (n = 120; X (n = 4) (n = 30; Mean (n = 5; Mean = (n = 5; Mean = 13.7; SD ± 0.8) = 10.9; SD ± 13; SD ± 0.7) = 14.7; SD ± Mean = 10.7; = 13.4; SD ± 12.6; SD ± 0.9) 12.4; SD ± 0.9) 1.0) 0.5) SD ± 1.0) 1.9) 27–29 32-37 22-28 20-33 24-33 17-31 27-34 22-41 21-27 16-19 (n = 4; Mean = (n = 6; Mean = (n = 20; Mean (n = 5; Mean = (n = 11; Mean (n = 117; Mean (n = 3; Mean = (n = 30; Mean (n = 5; Mean = (n = 4; Mean = 28; SD ± 1) 34.8; SD ± 1.7) = 25.1; SD ± 26.8; SD ± 4.7) = 28.2; SD ± = 21.3; SD ± 30.7; SD ± 3.5) = 29.4; SD ± 23.2; SD ± 2.4) 17.5; SD ± 1.3) 1.8) 2.6) 2.1) 3.6) 23–27 30-36 25-35 22-32 23-32 17-31 27-28 20-33 25-29 16-21 (n = 4; Mean = (n = 6; Mean = (n = 20; Mean (n = 5; Mean = (n = 11; Mean (n = 115; Mean (n = 4; Mean = (n = 30; Mean (n = 5; Mean = (n = 4; Mean = 24; SD ± 2) 32.7; SD ± 2.5) = 30.1; SD ± 27.4; SD ± 3.6) = 28.5; SD ± = 22.6; SD ± 27.7; SD =0.6) = 25.0; SD ± 27.4; SD ± 1.7) 18.3; SD ± 2.1) 3.1) 4.0) 2.5) 3.1) PVE 96 118-121 92-98 118 (n = 1) not available 92-102 144 (n = 1) 117-131 (n = 2) 117-124 (n = 2) 91 (n = 1) (n = 1) (n= 4; Mean = (n = 4; Mean = (n = 43; means 119.2; SD 1.3) 95.0; SD ± 2.4) = 97.1; SD ± 12.2) ……continued on the next page TABLE 1. (Continued) TABLE 1. (Continued)

Charact ers	bagual	cerradensis	infraorbitale	kisteumacheri	Species of Leposternon maximus microcephalum	octostegum	polystegum	scutigerum wuchereri
PEC COL PMXT	Many shields. All small and irregularly shape. Dark brown 5	Many shields. Mostly small and diamond- shaped. Absent 5	Many shields. All small and irregularly shape. Yellow 5–6	Many shields. Mostly small and diamond- shaped. Absent 7	Many shields. Many shields. Mostly small All small and and diamond- irregularly shaped. shape. Uniform Dark brown pinkish color pattern Not available 7	Few large shields. Almost as long as wide. Absent 1	Many shields. Mostly small and diamond- shaped. Absent and yellow. 1	Few large Few large shields. Almost shields. All as long as wide. relatively long and two times longer than wide. Yellow Dark brown 1 3, 5 and 7
MXT	4/4	4/4	4/4	4/4	Notavailable 4/4	3/3	2/2	5/5 3/3
DT	6/6	6/6	6/6	6/6	Notavailable 6/6	5/5	5/5	5/5 4/4 and 6/6
RPN RPMX FPMX	Present and contacting each other in the facial portion of skull. Present and contacting each other in the facial portion of skull. Present	Absent Absent Absent	Present, but relatively undeveloped and not contacting in the facial portion of skull. Present and not contacting in facial portion of skull. Present	Absent Absent Absent	Not available Present, but relatively undeveloped and not contacting in the facial portion of skull. Not available Present and not contacting in facial portion of skull. Not available Present	Absent Present and not contacting in facial portion of skull. Absent	Absent Absent Absent	Absent Present, but not contacting in the facial portion of skull. Absent Present and not contacting in facial portion of skull. Absent Present
HL/SV L RL/HL RW/H W	3.5–4.5 % (n = 3; Mean = 3.9; SD ± 0.5) 22.6–23.5% (n = 3; Mean = 23.3; SD ± 0.6) 64.0–68.1% (n = 3; Mean = 65.9; SD ± 2.1)	2.6–3.3% (n = 6; Mean = 2.8; SD ± 0.2) 20.3–23.1% (n = 6;Mean = 21.6; SD ± 1.3) 56.4–63.7% (n = 6; Mean= 60.2; SD ± 2.7)	3.3–5.1% (n = 17; Mean = 4.3; SD ± 0.5) 20.2–26.4% (n = 16; Mean = 23.9; SD ± 1.7) 49.3–74.3% (n = 17; Mean = 57.7; SD ± 7.4)	2. 6–3.3% (n = 3; Mean = 2.9; SD ± 0.4) 24.0–27.4% (n = 4; Mean = 25.7; SD ± 1.4) 56.7–63.0% (n = 4; Mean = 59.9; SD ± 2.9)	1.9–2.8% 3.0–5.1% (n = 11; Mean (n = 113; Mean = 2.2; SD ± 0.2) = 3.8; SD ± 0.4) 22.5–27.4% 21.9–33.7 % (n = 11; Mean (n = 115; Mean = 25.7; SD ± = 28.4; SD ± 1.7) 2.5) 57.9–75.4% 53.0–75.3% (n = 11; Mean (n = 115; Mean = 67.3; SD ± = 64.6; SD ± 5.0) 4.3)	2.3–2.9% (n = 4; Mean = 2,7; SD ± 0.3) 22.1–23.8% (n = 4; Mean = 22.9; SD ± 0.9) 56.9–84.2% (n = 4; Mean = 64.3; SD ± 13.3)	2.5–3.3% (n = 10; Mean = 2,7; SD ± 0.2) 28.9–34.3% (n = 14; Mean = 31.4; SD ± 1.6) 68.5–80.6% (n = 12; Mean = 71.9; SD ± 4.6)	2.7–3.2% 2.6–4.1% (n = 4; Mean = (n = 4; Mean = 3.0; SD ± 0.3) 3.1; SD ± 0.6) 28.3–29.3% 25.7–30.3% (n = 4; Mean = (n = 4; Mean = 28.9; SD ± 0.4) 27.6; SD ± 2.0) 78.6–84.3% 58.1–72.3% (n = 4; Mean = (n = 5; Mean = 81.4; SD ± 2.3) 67.4; SD ± 5.6) ……continued on the next page

Charact Species of Leposternon ers bagual cerradensis infraorbitale kisteumacheri maximus microcephalum octostegum polystegum scutigerum wuchereri AZL/H 29.3–35.0% 40.1–51.4% 29.9–41.1% 35.4–40.5% 39.9–48.9% 22.7–43.2 % not applicable, 15.2–27.2% Not applicable, 41.9–50.3% (n = 3; Mean = (n = 6; Mean = (n = 16; Mean (n = 3; Mean = (n = 8; Mean = (n = 96; Mean shield probably (n = 14; Mean shield absent. (n = 4; Mean = 33.0; SD ± 3.3) 40.7; SD ± 4.4) = 36.2; SD ± 37.4; SD ± 2.8) 45.02 ; SD ± 3.1) = 29.6; SD ± fused with = 18.8; SD ± 46.2; SD ± 3.8) 3.1) 3.8) frontals 3.2) AZW/ 35.6–45.8% 35.5–48.6% 36.1–58.0% 25.5–34.6% 29.6–69.2% 29.6–58.8 % 61.2–84.7% 13.7–20.4% Not applicable, 59.0–67.4% (n = 3; Mean = (n = 6; Mean= (n = 16; Mean (n = 3; Mean = (n = 11; Mean (n = 105; Mean (n = 4; Mean = (n = 12; Mean shield absent. (n = 4; Mean = 40.2; SD ± 5.2) 43.8; SD ± 4.4) = 44.9; SD ± 29.8; SD ± 4.6) = 56.9; SD ± = 44.0; SD ± 68.9; SD ± = 16.9; SD ± 63.0; SD ± 4.3) 5.6) 10.9) 5.7) 10.7) 2.4) /H 25.3–25.5% 21.9–27.8% 21.0–29.4% 28.9–36.6% 17.6–24.1% 15.2–30.6% Not applicable, 41.1–47.9% Not applicable, 36.0% (n = 2) (n = 4; Mean = (n = 16; Mean (n = 2, other (n = 8; Mean = (n = 90; Mean shield absent. (n = 5; Mean = shield absent. (n = 1; other 24.8; SD ± 2.5) = 25.0; SD ± specimens with 21.2; SD ± 2.1) = 22.8; SD ± 43.6; SD ± 2.6) specimens with 2.4) fusion frontals) 3.3) fused frontals) /HL 9.8–13.9% 7.5–8.3% 9.7–18.0% 4.8–9.4% 4.6–13.0% 7.6–17.8% Not applicable, 4.3–5.3% 9.2–11.3% Fusioned (n = 3; Mean = (n = 3; Mean = (n = 17; Mean (n = 3; Mean = (n = 9; Mean = (n = 94; Mean shield absent. (n = 2) (n = 2) parietals. 12.2; SD ± 2.1) 7.9; SD ± 0.4) = 13.6; SD ± 7.8; SD ± 2.6) 7.9; SD ± 2.5) = 12.4; SD ± 2.7) 2.3) TPL/H 18.9–22.0% 25.0–29.9% 15.8–27.4% 27.1–31.4% 14.3–44.3% 14.0–23.8% 27.5–31.8% 24.5–30.9% Not applicable, 16.4–18.0% (n = 3; Mean = (n = 5; Mean = (n = 17; Mean (n = 4; Mean = (n = 8; Mean = (n = 109; Mean (n = 4; Mean = (n = 12; Mean shield absent. (n = 3; Mean = 20.2; SD ± 1.6) 27.7; SD =1.7) = 20.1; SD ± 28.7; SD ± 1.9) 29.3; SD ± 8.1) = 19.0; SD ± 29.4; SD ± 2.0) = 27.2; SD ± 18.6; SD ± 1.9) 3.0) 2.3) 1.8) TPW/H 13.2–17.8% 22.1–31.0% 7.1–24.5% 20.3–31.1% 19.2–28.6% 9.3–42.2% 18.4–27.5% 29.9–39.5% Not applicable, 15.8–18.0% (n = 3; Mean = (n = 5; Mean = (n = 18; Mean (n = 4; Mean = (n = 10; Mean (n = 109; Mean (n = 4; Mean = (n = 12; Mean shield absent. (n = 3; Mean = 15.6; SD ± 2.3) 25.1; SD =3.2) = 15.8; SD ± 26.3; SD ± 4.5) = 24.7; SD ± = 19.7; SD ± 21.1; SD ± 4.3) = 34.8; SD ± 16.8; SD ± 1.1) 4.2) 3.0) 5.7) 2.8) PFL/H 23.0–26.8% 37.0–44.3% 20.6–36.9% 37.2–41.6% 22.2–27.2% 14.5–29.5% 36.4–41.3% 24.2–28.2% Not applicable, 20.9–26.1% (n = 3; Mean = (n = 5; Mean = (n = 16; Mean (n = 4; Mean = (n = 2) (n = 71; Mean (n = 4; Mean = (n = 5; Mean = shield absent. (n = 3; Mean = 24.8; SD ± 1.9) 39.6; SD =2.7) = 27.5; SD ± 39.4; SD ± 2.2) = 22.1; SD ± 37.8; SD ± 2.4) 26.0; SD ± 2.0) 23.0; SD ± 2.7) 4.3) 2.5) PFW/H 38.3–41.7% 18.9–27.3% 32.0–45.7% 25.4–36.7% Not available 28.4–52.0% 15.9–34.7% not available Not applicable, 41.6–49.7% (n = 3; Mean = (n = 5; Mean = (n = 16; Mean (n = 4; Mean = (n = 90; Mean (n = 4; Mean = shield absent. (n = 3; Mean = 39.5; SD ± 1.9) 21.6; SD =3.0) = 36.6; SD ± 28.8; SD ± 5.3) = 43.9; SD ± 24.5; SD ± 7.8) 44.9; SD ± 4.3) 4.3) 4.1) CML/H 53.4–59.1% 64.0–73.8% 49.2–69.6% 53.7–67.8% 56.7–64.5% 47.3–63.2% 61.0–69.7% 54.0–57.4% 58.9–59.5% 54.0–57.1% (n = 4; Mean = (n = 6; Mean = (n = 17; Mean (n = 4; Mean = (n = 2) (n = 91; Mean (n = 4; Mean = (n = 3; Mean = (n = 2) (n = 3; Mean = 56.9; SD =2.8) 68.1; SD =3.7) = 59.9; SD ± 62.1; SD ± 6.0) = 55.4; SD ± 65.5; SD ± 4.8) 55.7; SD=1.7) 0.7; SD ± 0.1) 5.6) 3.6) /SV 3.2–4.4% 2.4–3.2% 3.7–6.8% 2.6–3.0% 1.7–1.9% 2.5–5.5% 2.0–2.9% 1.6–2.7% 2.4–2.9% 1.9–2.9% (n =4; X = 3.7; (n = 6; Mean = (n = 17; Mean (n = 4; Mean = (n = 10; Mean (n = 111; Mean (n = 4; Mean = (n = 10; Mean (n = 4; Mean = (n = 5; Mean = SD =0.5) 2.7; SD =0.3) = 5.1; SD ± 0.9) 2.9; SD ± 0.2) = 1.8; SD ± 0.1 ) = 3.8; SD ± 0.5) 2.4; SD ± 0.3) = 2.4; SD=0.3) 2.6; SD ± 0.2) 2.4; SD ± 0.3) /SV 4.9–5.6% 4.9–5.8% 4.5–7.4% 5.3–6.7% 3.9–6.2% 3.8–7.5% 3.2–4.3% 4.2–5.0% 4.7–5.4% 4.6–5.8% (n =4; X = 5.3; (n = 6; Mean = (n = 17; Mean (n = 4; Mean = (n = 10; Mean (n = 114; Mean (n = 4; Mean = (n = 9; Mean = (n = 4; Mean = (n = 5; Mean = SD ± 0.3) 5.3; SD =0.4) = 5.6; SD ± 0.7) 5.8; SD ± 0.7) = 4.8; SD ± 0.7) = 5.5; SD ± 0.6) 3.7; SD ± 0.5) 4.6; SD=0.3) 5.0; SD ± 0.3) 5.3; SD ± 0.5) TABLE 2. Meristic and morphometric measurements (in millimeters) of the type series of Leposternon bagual sp. nov. Abbreviations of characters: CA, Caudal annuli; DAA, Dorsal anterior half-annuli; DPA, Dorsal postpectoral halfannuli; DS, Dorsal segments per half-annulus of midbody; F, female; HL, Head length; LA, Lateral half-annuli; M, male; MD, Midbody diameter; PV, Precloacal vertebrae; S, Sex; SC, Segments caudal (5th annulus); SVL, Snout-vent length; TL, Tail length; VPA, Ventral postpectoral half-annuli; VS, Ventral segments per half-annulus of midbody. Characters Holotype Paratypes Mean ±SD FML FML FML FML 11319 11312 11313 11318 Sex F M F M

DAA DPA VPA	18 253 214	16 266 211	17 240 206	15 232 + n* 205 + n*	16.5 253.0 210.3	± 1.3 ± 13.0 ± 4.0
CA LA DS	12 4/5 28	11 5/5 28	11 5/5 29	10 4/4 29	16.5 28.5	± 1.3 ± 0.6
VS CS HL	23 35 9.0	24 37 10.6	27 36 8.0	26 30 7.3	25.0 34.5 8.7	± 1.8 ±3.1 ± 1.4
SVL MD TL	257 9.2 14.5	294 9.4 15.5	178 7.9 8.8	ca. 174* 6.3 11.4	243 8.2 12.5	± 59.3 ±1.5 ± 3.0

* Specimen with mutilated body. FIGURE 5. Geographic distribution of Leposternon bagual sp. nov. Geographic distribution and habitat. So far, the new species is only known to occur in the type locality, El Bagual Ecological Reserve, located in the Province of Formosa , Laishi Department, Argentina ( Fig. 5 ). The Ecological Reserve has an extension of 3.336 ha within the fitogeographic region of the Humid Chaco, mainly dominated by floodplain pastures interspersed by forested areas ( Mercolli & Yanosky 2001 ).