The Systematics, Biogeography, and Natural History of the Endemic Papuan Snake Genus Toxicocalamus (Elapidae: Hydrophiinae)

Toxicocalamus Boulenger 1896, is a genus of front-fanged venomous snakes belonging to the Australo-Melanesian subfamily Hydrophiinae, in the near-global family Elapidae. It is endemic to the island of New Guinea, and its satellites, the d’Entrecasteaux and Louisiade Archipelagos, in Milne Bay Province, Papua New Guinea (PNG), off the southeastern tip of the Papuan Peninsula, and four small islands along the northern coast of Madang, East Sepik, and Sandaun Provinces, PNG. Currently twenty-four species are recognised, twelve of which have been described since 2009 (five involving this author as first or last author), with three species resurrected from synonymy, making Toxicocalamus the largest terrestrial, alethinophidian genus in the entire Australia-Pacific region. Yet, many species are poorly known, five species being only known from their holotypes, four from just two specimens, and a further five from fewer than ten specimens. Conversely, 189 specimens have been collected belonging to a single species in one relatively small area, accounting for 36% of all known Toxicocalamus specimens (520) in thirty collections worldwide. The diversity of this genus is set to increase still further over the next 1–3 years, as between four and six new species are awaiting description and the only subspecies will be elevated to specific status. Snakes in the genus Toxicocalamus vary greatly in size (less than 250 mm to 1.2 m), physique (bootlace slender to stout and robust), and even activity (diurnal and terrestrial to secretive and semi-fossorial/fossorial). They also exhibit a wide range of scale counts and scalation characteristics, which are useful in determining their identification: varying degrees of head scute fusion; dorsal, ventral and subcaudal counts; subcaudal and cloacal plate condition, and colouration or patterning. All species also share several biological or behavioural characteristics, i.e., all members are venomous (although the venom composition of only one species has been analysed) and some species exhibit extremely elongate venom glands that run into the body cavity, all species are believed to be vermivorous (worm-eating) and all are oviparous. Toxicocalamus is believed to occupy a basal position in the subfamily Hydrophiinae and its distribution across northern and central New Guinea, and on the southeastern and northern coast islands mirrors the underlying geology. Snakes in this genus are found primarily in those parts of New Guinea that originated as Pacific or Southeast Asian oceanic arcs and terranes, rather than the rump of southern New Guinea, which formed the vanguard of the Australian Craton, and therefore to understand the distribution of Toxicocalamus it is necessary to understand the geological and biogeographical history of the island of New Guinea itself.

Citation

O'Shea, M. (2025) The Systematics, Biogeography, and Natural History of the Endemic Papuan Snake Genus Toxicocalamus (Elapidae: Hydrophiinae). University of Wolverhampton. https://wlv.openrepository.com/handle/2436/626053

Publisher

University of Wolverhampton

URI

https://wlv.openrepository.com/handle/2436/626053

Type

Thesis or dissertation

Language

en

Description

A thesis submitted in partial fulfilment of the requirements of the University of Wolverhampton for the degree of Doctor of Philosophy by Published Works.

Collections

Theses and Dissertations