Philodryas patagoniensis

Philodryas patagoniensis (Girard, 1858) Figures 3 A, 3 B, 3 D, 3 E, 3 G, 3 H, 4 A, 4 B, 5 A, 5 B, 6 A, 6 B, 7 A – D, 9 A, 9 C, 9 E, 9 G, 10, 11 A, 11 B Callirhinus patagoniensis Girard, 1858: 182 Euophrys modestus Günther, 1858: 139 Pseudophis patagoniensis – Cope (1862: 348) Liophis poecilostictus Jan, 1863 a: 289 Dirrhox patagoniensis – Cope (1887: 58) Philodryas schottii (not Schlegel, 1837) – Boulenger (1896: 130, in part), Koslowsky (1898: 196, in part), Nágera (1915: 28), Devincenzi (1925: 47, in part) Chlorosoma schottii – Amaral (1929: 214, in part), 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), Vega and Bellagamba (1990: 12), Williams and Francini (1991: 75, in part), Cei (1993: 639, in part), Vega and Bellagamba (1994: 143), Tiranti and Avila (1997: 111), Achaval (2001: 7, in part), Carreira (2002: 36, in part), Giraudo and Scrocchi (2002: 32, in part), Carreira et al. (2005: 372, in part), Scolaro (2005: 66), (2006: 92), Scrocchi et al. (2010: 218), Wallach et al. (2014: 551, in part), Harrington et al. (2018: 71, in part), Nogueira et al. (2019: 221, in part), Di Pietro et al. (2020 a: 3), (2020 b: 7), Williams et al. (2021: 73, in part), Chuliver and Scanferla (2024: 10, in part) Common name. We propose changing the common name “ Patagonia green racer ” used for P. patagoniensis sensu lato to “ Patagonia maculated racer ” to better reflect the characteristics (i. e., distinctive maculation pattern) of P. patagoniensis sensu stricto. Lectotype. USNM 5536, an adult female from the mouth of the Río Negro, border of Río Negro and Buenos Aires provinces, Argentina (41.0241°S, 62.7896°W; elevation 0 m), collected by the U. S. Exploring Expedition under the command of Captain Charles Wilkes during 1838–1842. Referred specimens. We examined 213 museum specimens (see File S 1) from Argentina and Uruguay, corresponding to the B-morphotype. This collection included photographs of the lectotype, and also of the two syntypes of E. modestus, which were entirely consistent with our re-description of P. patagoniensis (see below), thereby confirming that name as a junior synonym of P. patagoniensis sensu stricto. Additionally, numerous photographs from citizen science platforms were analysed to enhance the distribution dataset, bringing the total number of B-morphotype specimens considered for this purpose to 322 (File S 1). Emended diagnosis. Philodryas patagoniensis 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 2.3 and 4.6 %, (3) SVL / TTL between 68.2 and 88.8 %, (4) TL / TTL between 11.2 and 31.8 %, (5) ventral scales between 159 and 193, (6) subcaudal scales between 57 and 109, (7) loreal markedly quadrate, (8) dorsal half of the preocular barely exceeds the posterior margin of the loreal, (9) supralabials 7 (3, 4), (10) lateral border of the supraocular concave in dorsal view, (11) first temporal scale short (height> 45 % of the length), (12) dorsal scales of the head brown, irregularly spotted with black, and bordered with wide black margins, (13) dorsal body design with maculated pattern, and (14) ventral scales exhibiting lateral black spots. Re-description of the lectotype. See Fig. 10. We examined photographs of the lectotype (USNM 5536) and found it to be entirely consistent with the Girard (1858) description and the Thomas (1976) enriched account. Additionally, we enriched the earlier descriptions as follows: (1) loreal supernumerary (2 / 2) and not 1 / 1 as is typical for the species, (2) dominant loreal (ventral) square-shaped with no dominant axis; (3) preoculars 1 / 1 with the dorsal half barely exceeding the posterior margin of the loreal; (4) postocular 2 / 2; (5) external border of the supraocular concave in dorsal view; (6) temporals 1 + 2, first temporal short (height representing 46 % of the scale length); (7) supralabials 7 (3, 4) / 7 (3, 4); (8) infralabials 9 (5) / 10 (6); (9) dorsal head scales (parietals, frontal, supraoculars) exhibit dark irregular areas and wide black scale borders; (10) dorsal scales with single apical pits; (11) uniform dorsal and head colouration; (12) lateral black spots present between successive ventral scales (a pattern blurred in the subcaudals); (13) 19–19 – 15 dorsal scales; (14) 182 ventral scales; (15) 69 subcaudal scales; and (16) tail short (TL / TTL = 17.6 %; calculated based on the measurements provided by Thomas in the description of the lectotype). Variation. In adult males, TTL ranges from 605 to 976 mm (mean: 747.2 ± 95.6 mm), HL from 18.5 to 30.6 mm (mean: 24.4 ± 2.9 mm), SVL from 425 to 752 mm (mean: 545.5 ± 73.1 mm), and TL from 161 to 259 mm (mean: 205.5 ± 25.8 mm); in adult females, TTL ranges from 622 to 1415 mm (mean: 981.1 ± 180 mm), HL from 20.3 to 39.4 mm (mean: 30.2 ± 4.7 mm), SVL from 471 to 1130 mm (mean: 765.8 ± 147.4 mm), and TL from 128 to 285 mm (mean: 218.5 ± 41.5 mm). Tables 2 and 3 summarise variations in pholidosis and measurements. In life, the colouration of P. patagoniensis (Fig. 11 A, B) exhibits two distinct patterns of dorsal and lateral head and body colouration, characterised by varying shades of brown and the presence of dorsal and lateral body maculation. It is important to note that maculation may not be uniformly expressed across the entire series of dorsal scales. The dorsal head scales (parietals, frontal, and supraoculars) typically display dark irregular areas with broad black scale borders. One of the two distinct patterns occurs in specimens from the Monte of Plains and Plateaus, Patagonian Forests, Steppe, southeast Espinal, and south Pampa ecoregions (Chubut, La Pampa, Mendoza, Neuquén, Rio Negro, southern San Luis, and southern Buenos Aires provinces). These specimens range from brown or black-brown on the dorsal and lateral head and maculated body areas, to pale brown in the non-maculated regions (Fig. 11 A). The point at which the lateral head colour transitions from dorsal brown to ventral pale yellow colour is variable, typically occurring near the supralabials. The second pattern is observed in specimens from the northern parts of the Pampa (mainly Buenos Aires province), Espinal (southern Santa Fe province), south-eastern Dry Chaco (Córdoba province), and the Pampa of south and central Uruguay (Fig. 11 B). These specimens exhibit a more homogeneous colouration across the dorsal head scales and the dorsal and lateral parts of the body, characterised by a pronounced brown (sometimes olive-brown) hue in the non-maculated areas, which renders the macula on the scales difficult to distinguish. Some specimens from both patterns exhibit paravertebral lines on the dorsal scales. The lateral areas of the head (the ventral half of the supralabials and infralabials), the gular region, and all ventral and subcaudal scales are pale yellow. The caudal edge of each supralabial is bordered in black. The pale-yellow ventral colouration is interrupted by black pigmentation on the ventral scales (less distinct on the subcaudals). This pigmentation forms lateral spots along adjacent scales’ anterior and posterior margins, sometimes producing a black line between them, which may be complete, incomplete, or absent. The tongue is bicoloured, with a red base and a black fork. The colouration in preservative remains similar to that observed in life, except in poorly preserved specimens or those fixed with aggressive concentrations of formalin, which tend to exhibit a general darkening of the scales (e. g., obscuring maculae and other scale patterns). Specimens that have been properly fixed and well preserved exhibit a slightly attenuated pattern compared to live individuals; for example, the ventral scales shift from pale yellow to beige or white. The contrast between the head and dorsal body colouration remains evident, although in slightly muted tones. Loss of the outermost scale layer can result in a lighter appearance (pale lavender; see Fig. 5 B). The overall head and body colouration could not be confirmed in specimens that were partially (one adult male from Neuquén province; MACN 30463) or fully melanistic (two adult males from Buenos Aires and Santa Fe provinces; MACN 48145 and MACN 27957, respectively). Notably, we observed an unusual body colouration in a single P. patagoniensis female (MACN 48160; Córdoba province), whose dorsal skin exhibited a black ring surrounding each scale, a pattern commonly seen in the new species described below. The hemipenes of P. patagoniensis are long and bilobed, with the maximum width occurring at the level of the lobes (width 2.8 to 3.5 times the length of the hemipenis). The lobes comprise approximately one-third of the total hemipenis length. On the sulcate face, the spermatic groove is bifurcated near the base, with both branches running parallel and close to each other before diverging approximately halfway along the hemipenis. The sulcate and asulcate faces exhibit longitudinal rows of elongated spines that increase in length distally. Among the eight hemipenes examined, the sulcate face displayed various spine configurations: 4 / 4, 4 / 6, 5 / 5 (n = 3), 5 / 6 (n = 2), and 7 / 7 (Fig. 7 A, C). The spines on the asulcate face showed configurations of 5 / 4, 5 / 5 (n = 5), 6 / 4, and 6 / 6 (Fig. 7 B, D). The asulcate face presents two longitudinal rows of large calyces extending over the body’s middle and distal portions and lobes. Additionally, the general reticulation of the lobes and the scattered distribution of the spinule patches resemble the descriptions of P. patagoniensis sensu lato provided by Thomas (1976; without specifying the origin of the specimens), Zaher (1999), Melo-Sampaio et al. (2021: fig. 2 C), and Scrocchi et al. (2024). Notably, the latter three studies based their descriptions on specimens from the distribution area of the species we describe below