The leaves are covered with star-shaped hairs, and the edges are wrinkled, turned down and finely toothed.

The flowers are arranged singly or in racemes of up to 5 on a red peduncle 30–40 mm (1.2–1.6 in) long near the ends of the branches.

The sepals are mauve and form a cup-shaped flower 10–15 mm (0.39–0.59 in) wide, the petals deep red and tiny.

[2][3][4][5] Thomasia petalocalyx was first formally described in 1855 by Ferdinand von Mueller and the description was published in his book Definitions of rare or hitherto undescribed Australian plants.

[3] Paper flower grows in forest, woodland, coastal heath and on granite outcrops in the Esperance Plains, Jarrah Forest and Mallee bioregions of southern Western Australia, in the south-east of South Australia, including on Kangaroo Island, and in scattered locations in the west and south-west of Victoria, with an isolated population on Wilsons Promontory, where it is common.