Pseudonaja mengdeni

Pseudonaja mengdeni grows up to a total length of 2 metres (6 ft 7 in) with an average length 1.2 metres (3 ft 11 in). It has slender body and narrow head. Mengden's brown snake is highly variable in colour and patterns, ranging from light brown to almost black, however it has two distinct forms: "orange with black head" and "pale head, grey nape". The underside along the belly is often cream, yellow, orange, or grey in colouration, frequently consisting of dark orange or grey blotches. Scales on the head often form a black V or W pattern. Western brown snakes can be confused with the eastern brown snake, which has a pink mouth lining; the northern brown snake has a purplish/blue-black mouth lining. P. mengdeni has a distinctive large strap-like scale around the front of the snout. To accurately identify this species the scales around the mid-body and along the lips need to be counted. 180-230 ventral scales, 45-70 subcaudals with a divided anal scale and 17 or 19 rows of smooth mid-body scales. However this must only be done by an experienced herpetologist, as a scratch from the fangs can still be fatal from P. mengdeni. Confusion between the species is largely due to the possible hybridisation between the Pseudonaja species. The western brown snake is often confused with other Pseudonaja spp. (brown snakes) and also Aspidites melanocephalus (black headed python).

It is found from the coast of Western Australia through central Australia to the north-west of New South Wales and western Queensland. The species distribution is poorly defined within its northern limits; however, it is absent from wetter areas of eastern Australia and south-western Western Australia. Pseudonaja mengdeni is found throughout all dry to arid areas including, woodlands, boree woodlands, sandhill woodlands, mallee woodlands, spinifex deserts, spinifex-covered dunefields, sandplains, stony plains, croplands, grasslands and temperate sclerophyll forests. The western brown snake is often found within fallen timber, dead trees, shrubs, native grasses and ground cavities.

Pseudonaja mengdeni preys upon small reptiles, mammals, other snakes, ground nesting birds and bird eggs.