The king brown snake (Pseudechis australis) is a species of highly venomous snake of the family Elapidae, native to northern, western, and Central Australia. Despite its common name, it is a member of the genus Pseudechis (black snakes) and only distantly related to true brown snakes. Its alternative common name is the mulga snake, although it lives in many habitats apart from mulga. First described by English zoologist John Edward Gray in 1842, it is a robust snake up to long. It is variable in appearance, with individuals from northern Australia having tan upper parts, while those from southern Australia are dark brown to blackish. Sometimes, it is seen in a reddish-green texture. The dorsal scales are two-toned, sometimes giving the snake a patterned appearance. Its underside is cream or white, often with orange splotches. The species is oviparous. The snake is considered to be a least-concern species according to the International Union for Conservation of Nature, though may have declined with the spread of the cane toad.
Its venom is not as potent as those of Australia's other dangerous snakes, but can still cause severe effects if delivered in large enough quantities. Its main effect is on striated muscle tissue, causing paralysis from muscle damage, and also commonly affects blood clotting (coagulopathy). Often, extensive pain and swelling occur, rarely with necrosis, at the bite site. Deaths from its bites have been recorded, with the most recent being in 1969. Its victims are treated with black snake (not brown snake) antivenom.
Taxonomy
The species was first described by English zoologist John Edward Gray in 1842 from a specimen collected at Port Essington in the Northern Territory. Gray saw little distinction from the Egyptian cobra (Naja haje) in his single preserved specimen—excepting the variation in ocular plates—and assigned the name Naja australis. On obtaining a second specimen from the College of Surgeons, Albert Günther of the British Museum recognised an affinity with the Australian species described as Pseudechis porphyriacus, resulting in the current combination as Pseudechis australis in the black snake genus Pseudechis. Scottish-Australian naturalist William Macleay described Pseudechis darwiniensis in 1878, from a more slender specimen that he thought was distinct from P. australis. Belgian-British zoologist George Albert Boulenger described P. cupreus in 1896 from a specimen collected from the Murray River, distinguishing P. darwiniensis from P. australis by the shape of the frontal scale. Austrian zoologist Franz Werner described Pseudechis denisonioides from Eradu, Western Australia in 1909. Australian naturalist Donald Thomson obtained a skull of a large specimen with a wide head collected from East Alligator River in Arnhem Land in 1914, naming it Pseudechis platycephalus in 1933. He distinguished it from P. australis on the basis of it having anteriorly grooved palatine and pterygoid teeth, and having blunt ridges and keels on the dorsal scales.
In 1955, Australian herpetologist Roy Mackay concluded that several species previously described were synonymous with P. australis, recognising that it was a highly variable taxon. He noted that P. australis had frontal scales of variable shape, and that grooves were present on the teeth of many specimens of Pseudechis, so these features did not support separate species. Australian herpetologists Richard W. Wells and C. Ross Wellington described Cannia centralis in 1985 from a specimen collected north of Tennant Creek in 1977, distinguishing it on the basis of a narrow head; however, the distinction was not supported by other authors. Two new species and a new genus have been described within this complex by Australian snake-handler Raymond Hoser—the eastern dwarf mulga snake (P. pailsei) from near Mount Isa, Queensland, Australia, and the Papuan pygmy mulga snake (P. rossignolii), found in Irian Jaya. Hoser later also resurrected the pygmy mulga snake (P. weigeli, originally described as Cannia weigeli by Wells and Wellington in 1987). These descriptions were initially received with skepticism due to the low level of evidence provided in the original descriptions.