Philodryas pseudomamba sp. nov.

Figures 3 C, 3 F, 3 I, 4 C, 5 C, 6 C, 7 E, 7 F, 9 B, 9 D, 9 F, 9 H, 11 C, 12

Dryophilax schottii (not Schlegel, 1837) – Duméril (1853: 112), Duméril et al. (1854: 1118)

Philodryas schottii (not Schlegel, 1837) – Günther (1858: 125), Jan (1863 b: 83), Hensel (1868: 332), Boettger (1885: 235), Boulenger (1886: 434), Cope (1895: 218), Peracca (1895: 18), Boulenger (1896: 130, in part), Koslowsky (1898: 196, in part), Devincenzi (1925: 46, in part), Ábalos et al. (1964: 264)

Pseudophis schottii – Cope (1862: 348)

Chlorosoma schottii – Amaral (1929: 214, in part), Amaral (1932: 101), Serié (1936: 51, in part)

Philodryas patagoniensis – Hoge (1964: 67, in part), Peters and Orejas-Miranda (1970: 244, in part), Thomas (1976: 172, in part), Williams and Francini (1991: 75, in part), Cei (1993: 639, in part), Lobo and Scrocchi (1994: 105), Fowler and Salomão (1995: 150), Leynaud and Bucher (1999: 30), Zaher (1999: 67), Achaval (2001: 7, in part), Giraudo (2001: 155), Carreira (2002: 36, in part), Giraudo and Scrocchi (2002: 32, in part), Carreira et al. (2005: 372, in part), Hartmann and Marques (2005: 25), López and Giraudo (2008: 474), Zaher et al. (2009: 121), Vidal et al. (2010: 53), Pyron et al. (2011: 337), Grazziotin et al. (2012: 443), Wallach et al. (2014: 551, in part), Cabral and Bueno-Villafañe (2015: 13), Cacciali et al. (2016 b: 240), Gouveia et al. (2017: 6), Harrington et al. (2018: 71, in part), Nogueira et al. (2019: 221, in part), Quintela and Loebmann (2019: 12), Zaher et al. (2019: 28), Arredondo et al. (2020: 6), Williams et al. (2021: 73, in part), Tioyama et al. (2023: 14), Chuliver and Scanferla (2024: 10, in part)

Pseudablabes patagoniensis – Melo-Sampaio et al. (2021: 37), Dubeux et al. (2022: 6)

Suggested common name.

South American dotted racer.

Holotype.

MLP.R 5449, an adult male from Colonia Carlos Pellegrini, San Martin department (28.5333°S, 57.1712°W; elevation 67 m), Corrientes Province, Argentina; collected by Cátedra de Herpetología, Facultad de Ciencias Naturales y Museo, Universidad Nacional de La Plata between 11 and 15 November 2008.

Paratypes (n = 14).

Argentina. Chaco Province: MLP.JW 1949 (adult female) from Juan José Castelli, General Güemes department, collected by I. Berkunsky in January 2001; MACN 38710 (adult female) from Resistencia, San Fernando department, collected by C. Schlinger on 19 November 1956. Corrientes Province: MACN 50189 (adult female) from Provincial Road 5 between San Luis del Palmar and Laguna Brava, San Cosme department, collected by B. Cajade and E. Nenda on 30 July 2017; MACN 48195 (adult male) from Yapeyú, San Martín department, collected by Ayudantía Marítima Yapeyú on 6 September 1965. Entre Ríos Province: MACN 48165 (adult female) from the surroundings of La Paz, La Paz department, collected by M. Baldi on 7 November 1975; MACN 48163 (adult female) from Pronunciamiento, Uruguay department, collected on 30 October 1967. Formosa Province: MACN 48134 (adult male) from Bartolomé de Las Casas, Patiño department. Misiones Province: MACN 48166 (adult female) from Posadas, Capital department, collected on 24 April 1966. Santa Fe Province: MLP. R 6445 (adult male) from 4 km NE of Aguará Grande, San Cristóbal department, collected by L. Alcalde, M. J. Cassano and M. B. Semeñiuk on 29 October 2016; MLP. R 6434 (adult male) from Provincial Road 3 in Los Tábanos, Vera department, collected by L. Alcalde, M. J. Cassano and M. B. Semeñiuk on 21 October 2016; MLP. R 6450 (adult female) from Provincial Road 3 near Vera, Vera department, collected by L. Alcalde, M. J. Cassano and M. B. Semeñiuk on 25 October 2016; MLP. R 6455 (adult male) from road cross between Provincial Road 3 and National Road 11 near Vera, Vera department, collected by L. Alcalde, M. J. Cassano and M. B. Semeñiuk on 25 October 2016. Santiago del Estero Province: MACN 4325 (adult male) form Malbrán, Aguirre department, collected by Cazale and Peyrade. — Brazil: São Pablo State: MACN 36703 (adult female) from the surroundings of Ibiúna, Ibiúna municipality, collected by Instituto Butantán in April 1996.

Referred specimens.

For the species description, 178 museum specimens corresponding to the A-morphotype were examined (File S 1), including those from the type series. In addition, numerous photographs from citizen science platforms were analysed to enhance the distribution dataset, bringing the total number of A-morphotype specimens considered to 403 (File S 1).

Etymology.

The prefix pseudo of the epithet derives from Greek, meaning “ falseness ” or “ falsehood ”. Mamba refers to the term “ imamba ” used in the Bantú language (spoken by various African ethnic groups) to designate snakes of the genus Dendroaspis, commonly known in English and other languages as “ mambas ”. The species name was explicitly inspired by D. polylepis (the black mamba), due to the general physical resemblance and notably aggressive behaviour shared by both species.

Diagnosis.

Philodryas pseudomamba sp. nov. differs from all other species of the genus by the following combination of characters: (1) dorsal scale rows 19–19 – 15, (2) HL / TTL between 2 and 3.4 %, (3) SVL / TTL between 68 and 77.7 %, (4) TL / TTL between 22.2 and 32 %, (5) ventral scales between 166 and 199, (6) subcaudal scales between 81 and 124, (7) loreal scale rectangular, longer than tall, (8) dorsal half of the preocular markedly exceeding the posterior margin of the loreal, (9) supralabials 7 (3, 4), (10) lateral border of the supraocular straight in dorsal view, (11) first temporal scale large (height being less than 40 % of the length), (12) dorsal scales of the head with completely immaculate olive colouration featuring tiny black scale margins, (13) dorsal body design dotted, not maculated, and (14) ventral scales lacking lateral black spots.

Description of the holotype.

See Figs 3 C, 3 F, 3 I, 4 C, 5 C, 6 C, 12. Adult male, TTL of 910 mm, HL of 27.3 mm, SVL of 645 mm, and TL of 265 mm; proportions, HL / TTL = 3 %, SVL / TTL = 70.8 %, and TL / TTL = 29.2 %.

Morphological features include: loreals 1 / 1 (square-shaped with a dominant cranial-caudal axis, longer than tall), preoculars 1 / 1 (with the dorsal half markedly exceeding the half of the loreal), postoculars 2 / 2, temporals 1 + 2 / 1 + 2 (the first temporal is long, with the height representing 35 % of the scale length), supralabials 7 (3, 4) / 7 (3, 4) with the 5 th and 6 th being larger than the others (Fig. 3 C), infralabials 9 (5) / 9 (5) (Figs 3 C, 3 I), and external border of the supraocular straight or slightly expanded laterally in dorsal view (Fig. 3 F). Dorsal scales 19–19 – 15, smooth, with single apical pits (Figs 4 C, 5 C). There are 176 ventral scales and 104 subcaudal scales, anal and subcaudals are divided.

In preservative, the dorsal surfaces of the head and neck are olive brown, closely matching the colouration of the dorsal body (Fig. 12). The ventral surface of the head is beige-white, with the dorsal-ventral colour transition occurring at the midpoint of the supralabials (Fig. 3 C). The dorsal head scales lack dark markings and exhibit fine black interscale sutures (Fig. 3 F). Paravertebral lines evident, the dorsal scales display dark spots at their anterior and posterior ends, which converge between adjacent scales to form a single dot (Figs 4 C, 5 C, 12). Many dorsal scales have lost their outermost layer, resulting in a lighter, pale lavender appearance (Fig. 12). Ventral scales are beige-white, each separated by a continuous black interscale line (Fig. 6 C), which becomes blurred along the subcaudal region (Fig. 12).

The hemipenes of the holotype of P. pseudomamba sp. nov. are long and bilobed, with the lobes comprising approximately one-third of the total hemipenial length. The maximum width occurs at the level of the lobes and corresponds to 3.1 times the hemipenial length. The branches of the spermatic groove bifurcate near the base of the hemipenis and run in close parallel before diverging at approximately the midpoint of the organ. The sulcate and asulcate faces bear longitudinal rows of enlarged spines that increase in height distally. On the asulcate face, the spine configuration is 5 / 6, and on the sulcate face, 6 / 6 (Fig. 7 E, F). The counts of the sulcate face begin at the bifurcation point of the spermatic groove toward the distal end (i. e., spines posterior to this point were considered spinules). Two longitudinal rows of large calyces are on the asulcate surface, covering the middle and distal portions of the body and lobes. These calyces are associated with a profuse reticulation of the lobes and randomly distributed patches of spinules. Overall, the hemipenial morphology of the holotype resembles that described by Zaher (1999), Melo-Sampaio et al. (2021: fig. 2 C), and Scrocchi et al. (2024) for specimens whose geographic distribution corresponds to P. pseudomamba sp. nov.

Variation.

In adult males, TTL ranges from 618 to 1207 mm (mean: 954.3 ± 138.8 mm), HL from 21.1 to 33.1 mm (mean: 28 ± 3.1 mm), SVL from 435 to 871 mm (mean: 678.5 ± 104.5 mm), and TL from 183 to 343 mm (mean: 275.7 ± 43.3 mm); in adult females, TTL ranges from 672 to 1552 mm (mean: 1135 ± 191.9 mm), HL from 22.9 to 39.4 mm (mean: 32 ± 4.3 mm), SVL from 497 to 1170 mm (mean: 849.7 ± 142.9 mm), and TL from 175 to 382 mm (mean: 285.2 ± 52.1 mm). Tables 2 and 3 summarise variations in pholidosis and measurements.

The colouration in life (Fig. 11 C) is less variable than that observed in P. patagoniensis. A consistent difference in colouration exists between the head and neck compared to the rest of the body. Depending on the individual, the dorsum and laterals of the head and neck range from ochre to orange. The body dorsum is typically olive but may also appear as mint green or olive green. Each dorsal scale bears a subtle dark spot at its anterior and posterior ends, with the anterior spot being less pronounced than in P. patagoniensis. These spots on adjacent scales converge to form a single dot, rather than a maculation as seen in P. patagoniensis, except in juveniles. The aggregation of these dots along the same dorsal scale row forms oblique lines oriented ventro-dorsally and cranially-caudally. In both dorsal and lateral views, these oblique lines give the dorsal scales a pectinated appearance on either side of the mid-vertebral line. Continuous paravertebral lines formed between subsequent scales are more frequently observed than in P. patagoniensis.

The ventral colouration of the head and body is pale yellow. The boundary between the dorsal ochre and the ventral pale-yellow lies below the midpoint of the supralabials. The black pigmentation along the sutures of the head scales is more delicate than in P. patagoniensis, particularly in the parietals, frontal, and supraoculars, which also lack the irregular dark markings characteristic of P. patagoniensis. The pale yellow ventral colouration is occasionally interrupted by black lines between successive ventral scales. Each of these lines is typically continuous, although they may less frequently be interrupted at the mid-ventral region. In the subcaudal region, this pattern becomes progressively blurred. The tongue is bicoloured, displaying a red base and a black fork.

In preservative, the colouration resembles that observed in life, except in poorly preserved specimens. Adequately fixed and well-preserved specimens appear pale compared to live specimens. For example, the ventral scales often fade from pale yellow to beige or white, and the contrast between the head and dorsal body colouration becomes less distinct. Although melanistic specimens are frequently found in collections (e. g., MACN 10228 or MACN 39619), we did not encounter melanism during our fieldwork. Typical head and body patterns are entirely or partially obscured in these melanistic specimens. Furthermore, black rings surrounding dorsal scales are present in some specimens and appear more frequently than in P. patagoniensis (e. g., MACN 7841, MACN 48179).

The other specimen examined for hemipenial morphology differed from the holotype in a single aspect: it exhibited a 5 / 5 configuration of the elongated spines on the sulcate and asulcate faces.

Comparison.

The dorsal scale rows distinguish Philodryas pseudomamba sp. nov. (19–19 – 15) from P. agassizii (13–13 – 13), P. varia (17–17 – 13 to 19–17 – 13; Thomas 1976), P. livida (17–17 – 15), P. boliviana (15–17 – 13 to 17–17 – 13; Thomas 1976), P. baroni (ranging from 21–21 – 17 to 23–23 – 17; Thomas 1976), P. nattereri (from 21–21 – 15 to 21–22 – 17; Thomas 1976), and P. trilineata (21–23 – 17 to 26–23 – 17; Thomas 1976). The absence of a dorsal colour that shifts from green in the anterior half of the body to brown in the posterior part distinguishes P. pseudomamba sp. nov. from P. erlandi and P. mattogrossensis, which exhibit a dorsal colour shift between the mid and posterior body. The lack of well-defined broad stripes on the body distinguishes P. pseudomamba sp. nov. from P. chamissonis and P. psammophidea, both of which possess stripes. Both P. aestiva and P. olfersii display a uniform green colouration on the dorsum and flanges of the body and tail, which is absent in P. pseudomamba sp. nov. Additionally, P. aestiva differs in having keeled dorsal scales (smooth dorsal scales in P. pseudomamba sp. nov.), while P. olfersii typically features a black ocular stripe, which is always absent in P. pseudomamba sp. nov. The rare P. cordata can be distinguished from P. pseudomamba sp. nov. by its entirely black tongue (bicoloured in P. pseudomamba sp. nov., with a red base and black fork), and its hemipenial features, which are markedly divergent from those described in all Philodryas species. Certain body proportions are useful to distinguish between P. pseudomamba sp. nov. and P. arnaldoi (Amaral 1932). In P. pseudomamba sp. nov., the tail is shorter (mean TL / TTL <27 % for both sexes) than in P. arnaldoi (> 46 %).

Lastly, P. pseudomamba sp. nov. differs from P. patagoniensis by (character states of the former in parenthesis): (1) head and body shorter (larger), (2) short tail (large), (3) subcaudal scales 57–109 and ventral scales 159–193 (high number in both cases: 81–124 subcaudal scales and 166–199 ventral scales), (4) loreal scale markedly quadrate with no dominant axis, and the dorsal half of the preocular barely exceeds the posterior margin of the loreal (loreal scale is rectangular, longer than tall, with the dorsal half of the preocular markedly exceeding the posterior margin of the loreal), (5) external border of the supraocular concave in dorsal view (straight in dorsal view), (6) first temporal scale shorter, with the height representing more than 45 % of the length (longer than it is tall, with the height being less than 40 % of the length), (7) parietal, frontal, and supraocular scales brown, irregularly spotted with black, and bordered with wide black margins (completely immaculate olive colouration featuring tiny black scale margins), (8) dorsal scales exhibit a maculated pattern (not maculated), (9) lateral black spots present in the ventral scales (absent), (10) vomerine processes of the premaxilla sub-parallel (slightly divergent), (11) dorsal lamina of the nasal robust with non-concave posterolateral flange (dorsal lamina of the nasal slender with concave posterolateral flange), (12) three pointed and double-notched anterior ends of the parabasisphenoid (two pointed and single median-notched), and (13) rounded maxillary process of the palatine (triangular).

Distribution.

See Fig. 1. Philodryas pseudomamba sp. nov. is distributed across five countries: Argentina, Bolivia, Brazil, Paraguay, and Uruguay. In Argentina, the species occurs in 12 provinces: Buenos Aires, Chaco, Córdoba, Corrientes, Entre Ríos, Formosa, Misiones, San Luis, Santa Fe, Santiago del Estero, Tucumán, and Jujuy. It inhabits nine ecoregions (Delta and Islands of the Paraná and Uruguay Rivers, Dry Chaco, Espinal, Fields and Weeds, Humid Chaco, Ibera’s Marshlands, Pampa, Paranaense Forest, and Yungas Forest), and 33 regional complexes (sensu Morello et al. 2012).

In Uruguay, P. pseudomamba has been recorded in seven departments: Artigas, Cerro Largo, Paysandú, Río Negro, Rivera, Salto, and Tacuarembó. It occurs in four ecozones: Western Sedimentary Basin, Basaltic Slope, Gondwanic Sedimentary Basin, and Eastern Hills (Brazeiro et al. 2012). In Paraguay, this species occurs in six departments: Alto Paraná, Central, Misiones, Ñeembucú, Paraguari, and Presidente Hayes. It inhabits two ecoregions: Alto Paraná and the Atlantic Forest, and the Humid Chaco (Ávila Torres et al. 2018). In Bolivia, the species has been recorded in the Santa Cruz department, and the Gran Chaco and Chiquitano Dry Forest ecoregions (Ibisch et al. 2003). In Brazil, P. pseudomamba sp. nov. occurs in 14 states: Bahia, Distrito Federal, Goiás, Mato Grosso, Minas Gerais, Paraíba, Paraná, Rio de Janeiro, Rio Grande do Norte, Rio Grande do Sul, São Paulo, Santa Catarina, Sergipe, and Espírito Santo. Its distribution spans five major Brazilian biomes: Atlantic Forest, Caatinga, Cerrado, Pampa, and Pantanal (IBGE 2019).