#madtsoiidae

Wonambi is an extinct genus of madtsoiid snakes that lived throughout Australia from the in late Neogene to late Quaternary some 23 million to 50,000 years ago. The first remains of wonambi consisting of a partial skeleton were uncovered in the town of Naracoorte in South Australia. It was given the name Wonambi from the description, by the local Aboriginal people, of a serpent of the Dreamtime. This serpent, a mythological being commonly referred to by both Aboriginal people and Europeans as the Rainbow Serpent, was often held responsible for the creation of major features of the landscape. The family of this genus, Madtsoiidae, became extinct in other parts of the world around 55 million years ago, but continued to thrive on the island continent of Australia where they persisted well into the Pleistocene. There are two known species, Wonambi naracoortensis which reached 12-23ft (4-7m) in length and 100 -300lbs (45- 136kg) in weight, and the smaller Wonambi barriei which reached 6.5 -10ft (2-3m) in length. Although not closely related to pythons, madtsoiids shared a similar way of feeding; slowly suffocating prey before swallowing it whole. However they possessed uniquely robust skulls that were unable to fully disartuculate there jaws like many modern snakes can, which means that even the larger examples of Wonambi would have had to feed fairly small prey. It is believed that wonambi would have inhabited woodlands, grasslands, and scrublands spending its time near creeks and watering holes where it would ambush prey such as wallabies, birds, lizards, kangaroos, and other marsupials which came to drink.

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Almost-Living Fossils Month #14 -- Ancient Snakes

While the evolutionary origin of snakes is still rather poorly understood, one very early branch of their lineage -- known as the madtsoiids -- were a particularly long-lived group.

Originating back in the mid-Cretaceous (~100 mya), these “primitive” snakes were found mostly in the southern continents of Gondwana (known from South America, Africa, India, and Australia), but a few also spread into Europe. They were either some of the earliest true snakes or perhaps ophidians very closely related to them, and may have retained small hindlimbs that were slightly more well-developed than the vestigal ones of some modern snakes.

They ranged in length from under 1m (3′3″) to at least 7m (23′), with biggest of them rivaling some of the very largest living snakes in size.

They would have been similar to pythons, non-venomous and relying on constriction to kill their prey, although they had less flexible skulls than their modern relatives and couldn’t easily swallow animals much larger than their own heads. At least some of the Cretaceous species would have preyed on smaller dinosaurs, with one fossil even preserving a mid-sized madtsoiid in a sauropod nest alongside a hatchling.

Although the madtsoiids survived the end-Cretaceous extinction quite well and kept going throughout most of their range for the first half of the Cenozoic, most of them eventually disappeared in the Eocene-Oligocene extinction about 33 million years ago.

Aside from a single possible Late Olgiocene/Early Miocene record from South America (~29-21 mya), after that point the madtsoiids were found only in Australia, where they persisted almost into modern times.

Wonambi naracoortensis was one of the last of the Australian madtsoiids, living from the mid-Miocene (~11 mya) to at least the Late Pleistocene (~40,000 years ago). It was also one of the larger members of the group, 5-6m long (16′5″-19′8″), and seems to have been an ambush predator that lurked around waterholes to catch drinking animals.