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[B, E, H] Philodryas patagoniensis (Girard, 1858); [C, F, I] Philodryas pseudomamba Pietro, Sánchez, Poljak & Alcalde, 2026 |
Abstract
We analysed the genetic and morphological variation in Philodryas patagoniensis, a widely distributed South American racer snake. Two well-differentiated haplogroups were identified using mitochondrial gene sequences (12S and 16S) and the nuclear gene c-mos. Genetic divergence between these haplogroups correlates strongly with morphological differences, allowing the recognition of two morphotypes within P. patagoniensis. We integrated genetic and morphological data into a total evidence analysis using parsimony. Our results support the distinction between the two haplogroups/morphotypes, consistent with recognising two species within P. patagoniensis. Accordingly, we re-describe P. patagoniensis, refining its morphological variation and geographical distribution to reflect the observed genetic differentiation, and describe a new species. Morphological characteristics can distinguish the two species, including body measurements, scale patterns, and cranial osteology. The new species differs from P. patagoniensis sensu stricto in traits associated with arboreal habits, which are strongly correlated with the distribution of the two taxa across forested and open habitats in South America. Furthermore, P. patagoniensis sensu stricto has a significant Lycosa spider component in its diet, which is absent in the newly described species.
Keywords: Biodiversity, Dipsadinae, Philodryadini, Serpentes, South America, systematics, taxonomy
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| In-life colouration of A a Monte of Plains and Plateaus specimen of P. patagoniensis (Rio Negro, Chipauquil, Meseta de Somuncura), B a Pampa specimen of P. patagoniensis (Buenos Aires, Sierra de Curamalal), and C a Humid Chaco specimen of P. pseudomamba sp. nov. (Chaco, Tres Isletas). Photos are not to scale. Photo credits: David Vera (A), Eduardo Schaeffer (B). |
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| Lateral (A–C), dorsal (D–F), and ventral (G–I) views of the heads of representative specimens from both morphotypes. The left column (A, D, G) shows a B-morphotype specimen from the Monte of Plains and Plateaus (Rio Negro province, MLP.R 5313). The middle column (B, E, H) features a B-morphotype specimen from the Pampa (Buenos Aires province, MLP.R 6039). The right column (C, F, I) presents an A-morphotype specimen from the Humid Chaco (Corrientes province, MLP.R 5449, holotype). Arrows and asterisks highlight character states (see File S2). Photographs A–F include a line-drawing diagram highlighting in grey the scales involved in each character state, as indicated by arrows and asterisks in the corresponding images. Scale bars = 5 mm. |
Philodryas pseudomamba sp. nov.
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.
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.
Diego Omar Di Pietro, Julieta Sánchez, Sebastián Poljak and Leandro Alcalde. 2026. Morphological and Molecular Variation reveal Cryptic Diversity in the Racer Philodryas patagoniensis (Girard, 1858) (Squamata: Colubridae). Vertebrate Zoology. 76: 93-119. doi.org/10.3897/vz.76.e169219 [10 Feb 2026]