Australian Blue Riverdamsel

Pseudagrion crenatum is a slender blue-and-black damselfly belonging to the Pseudagrion blue-group. Males have blue markings on the head, thorax and abdomen, with black dorsal markings on the abdominal segments. The species is distinguished from related species by the shape of the male appendages. The tips of the appendages are deeply divided when viewed from the side.

Pseudagrion crenatum occurs in northern and eastern Australia, Indonesian West Papua and Papua New Guinea. In Australia it is found mainly in tropical and subtropical regions. Species of Pseudagrion typically inhabit streams, rivers and still waters with emergent vegetation.

In 2026, Malte Seehausen and Milen Marinov described Pseudagrion crenatum as a new species during a revision of the Pseudagrion microcephalum complex. The species was separated from Pseudagrion microcephalum on the basis of differences in the male appendages. Prior to this revision, Australian populations of this species had generally been identified as Pseudagrion microcephalum, a species then considered to be widespread across southern and eastern Asia, Australasia and the Pacific. Seehausen and Marinov restricted Pseudagrion microcephalum to the Indian subcontinent and recognised several distinct regional taxa, including Pseudagrion crenatum in Australia and New Guinea.