Morelia amethistina is a non-venomous species of snake, known as the amethystine, scrub python or Sanca permata locally, found in Indonesia, Papua New Guinea and Australia. Popular among reptile enthusiasts, and noted for its coloration and size, it is one of the six largest snakes in the world, as measured either by length or weight, and is the largest native snake in Australia and Papua New Guinea. There are currently four subspecies of the nominate race, Morelia amethystina amethystina, which are generally recognized. The Mollucan islands, including Halmahera, Ternate and Tidore are home to Morelia a. tracyei. The Tanimbar Islands are home to a smaller subspecies, Morelia a. nauta. On the island of Seram, Morelia a. clastolepis can be found, and mainland PNG (including the Indonesian western half, once called Irian Jaya—now West Papua) and many of its near offshore islands Morelia a. amethystina is quite common. In Australia, Morelia a. kinghorni is represented.
Specimens have reportedly been measured at more than 8.5 m (27.9 ft) in total length, but this is exceptional, as 5 m (16.4 ft) specimens are already considered large. As is typical for very large constricting snakes, almost no verified specimens of this species have exceeded 6 m (19.7 ft). However, in 1990, while conducting a herpetological survey, Tom Mendelson collected a wild female specimen on Biak Island, far Eastern Indonesia, which measured 22 feet 7 inches. Another huge female, in a report considered reliable by the staff of the Guinness Book of World Records, was measured by S. Dean in 1954 as 7.2 m (23.6 ft). A typical adult specimen will measure around 2 to 4 m (6.6 to 13.1 ft). Females typically weigh around 15 kg (33 lb). Some exceptional specimens have been confirmed to weigh over 30 kg (66 lb) and unconfirmed outsized specimens have been reported to scale 90 kg (200 lb), although no specimen of this enormous size has been authenticated. Males are much smaller and slimmer, averaging at 5.1 kg (11 lb) in mass at maturity, and occasionally weighing upwards of 11 kg (24 lb). The body is relatively slim, unlike those of many other large members of this family.
The specific name, amethistina, is an allusion to the milky iridescent sheen on its scales, which gives it an amethyst-like color.
The smooth dorsal scales are arranged in 39–53 rows at midbody. There are deep pits on 6 or 7 of the posterior lower labials.
Found in Indonesia (Maluku Islands, Timur Laut Islands, Banda, Kai Islands, Aru Islands, Misool, Salawati, most of Western New Guinea, many islands in Geelvink Bay, such as Biak, Numfor, Yapen and Supiori), Papua New Guinea (including Umboi Island, Bismarck Archipelago, Trobriand Islands, the d'Entrecasteaux Islands to Rossel Island, Louisiade Archipelago), and Australia (on some islands in the Torres Strait, the northern Cape York Peninsula south including the Atherton Tableland and the eastern foothills of the Great Dividing Range). The type locality is unknown.
Occurs in both bushland and suburbia. In Indonesia and northern tropical Queensland, Australia, it is found mostly in rainforests. Warm, humid habitats with good water sources are preferred.
In northern Australia and New Guinea, it mostly lives in scrublands.
The diet generally consists of birds, bats, rats, possums, and other small mammals. Larger Australian and Papuan specimens will catch and eat wallabies, and cuscus, waiting by creek and river banks for prey seeking drinking water.
According to McDiarmid et al. (1999), all cases in which the specific name was spelled with a y follow Daudin's (1803) Python amethystinus and are therefore unjustified emendations.