A New Species of New Guinea Worm-Eating Snake (Elapidae: Toxicocalamus Boulenger, 1896), with Comments on Postfrontal Bone Variation Based on Micro-computed Tomography
Morphology and DNA sequences are used to describe a new species of New Guinea Worm-Eating Snake (Elapidae: ToxicocalamusBoulenger, 1896) from Papua New Guinea: Toxicocalamus goodenoughensis n. sp., endemic to Goodenough Island of the D'Entrecasteaux Archipelago. Toxicocalamus goodenoughensis morphologically most closely resembles T. pachysomusKraus, 2009, but it differs by having undivided nasal scales completely surrounding nares (vs. divided), pale yellow markings on supralabials (vs. purple), a yellow nape band (vs. unbanded uniform nape), a dark gray-brown dorsum (vs. medium brown), dark brown mottling on yellow ventral scales, darkening toward cloaca (vs. uniform light brown), and >175 ventral scales. Phylogenetically, T. goodenoughensis is sister to another D'Entrecasteaux endemic, T. nigrescens Kraus, 2017. Coalescent-based species delimitation found the new species to be uniquely delimited from all other taxa (n = 13) in all combinations of parameters settings. Micro-computed tomography (μCT) scanning revealed the presence of distinctive variation in postfrontal bone morphologies, with three morphotypes exhibited within the genus: directed forward, directed lateral/perpendicular to cranium, and absent. Toxicocalamus goodenoughensis was found to have a sickle-shaped and directed forward postfrontal bone. The directed forward morphotype was shared by T. loriae clade 3 (sensu Strickland et al., 2016), T. mintoni, T. nigrescens, and T. pachysomus. Our work is the most comprehensive phylogenetic analysis of the genus and the first study using μCT scanning for comparative morphology of Toxicocalamus. We also provide an updated dichotomous key for the genus.ABSTRACT
Map showing southeast New Guinea and the D'Entrecasteaux, Louisiade, Trobriand, and Woodlark archipelagos with localities of included Toxicocalamus spp. Inset shows an outline of New Guinea, with focal region represented in the highlighted black border. The map legend specifies species and associated symbols.
Photos in life showing (A) Toxicocalamus goodenoughensis n. sp., holotype (LSUMZ 98043); (B) Toxicocalamus goodenoughensis paratype (LSUMZ 98042); and (C) an earthworm regurgitated by T. goodenoughensis (paratype, LSUMZ 98042) after collection, Casio watch case diameter, 44 mm.
Toxicocalamus goodenoughensis n. sp., showing the (A) dorsum of T. goodenoughensis holotype (LSUMZ 98043), (B) venter of holotype, (C) right view of head of holotype, (D) dorsum of T. goodenoughensis paratype (LSUMZ 98042), (E) venter of paratype, and (F) right view of head of paratype. Scale bars aside dorsum and venter images (A), (B) and (D), (E) are each 2 cm. Scale bars aside head images (C) and (F) are each 5 mm.
Line drawings highlighting head scalation of the holotype. Left (A) and (B) dorsal view of the T. goodenoughensis holotype (LSUMZ 98043). The scale bar for (A) and (B) is 6 mm.
μCT scans of the new species, highlighting postfrontal bone variation compared with selected congeners. Each species is represented by a right and dorsal view and then a close up of the postfrontal bones. Postfrontal bones were photographed in direction and orientation that they are attached to the skull to highlight the difference in angles. All skull scale bars are 5 mm. All postfrontal bone scale bars are 1 mm, except that of (F), which is 0.5 mm. (A–C) Holotype (LSUMZ 98043) of T. goodenoughensis n. sp. (D–F) Paratype (LSUMZ 98042) of T. goodenoughensis. (G–I) A voucher (LSUMZ 93563) of T. loriae clade 3. (J–L) Holotype (BPBM 20822) of T. mintoni. (M–O) Holotype (BPBM 16545) of T. nigrescens. (P–R) Holotype (BPBM 15771) of T. pachysomus. (S–U) Holotype (AMNH 76660) of T. holopelturus. (V–X) Holotype (AMNH 85745) of T. spilolepidotus.
Toxicocalamus spp. phylogeny representing 11 of the 16 proposed species, based on the concatenated sequence alignment. Also included are undescribed clades of cryptic diversity identified as T. loriae (see Strickland et al., 2016). Phylogeny was inferred using RAxML. Circles above branches correspond to bootstrap support values: black meaning ≥95 and white meaning 75–94. Circles below branches correspond to posterior probabilities produced by MrBayes: black meaning ≥0.95 and white meaning 0.85–0.94. Bootstrap support or posterior probabilities below 75 or 0.85, respectively, have been indicated. Symbols aside species relates to localities on Figure 1. There was 100% concordance between RAxML and MrBayes trees of the concatenated dataset.
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