According to the protologue: elytra orange with premedial dark markings reduced to a sutural spot (+/- a small spot over the humeral callus on each side); coppery coloration elsewhere with widespread blue reflections; (also the characteristic features of the C. sexplagiata group such as reduction in tarsal pads and the triangular aedeagus).

This species was described by Barker 2005 based on three specimens collected by Sundholm, Scott and de Keyzer from Grevillea pterosperma flowers in the Great Victoria Desert, on Goog Track N of Ceduna.

Virtually identical specimens to those of the type collection, with orange elytra and reduced fasciae, have now been collected from the MU Region (Murray Mallee) and northern SE Regions. However, there are also some that show evidence of intergradation towards larger forms with red elytra and complete (or largely complete) fasciae, traits which have been considered to characterise C. piliventris in SA.

There is some question as to whether C. keyzeri should be treated as a different to Castiarina piliventris (Saunders, 1868), at least at species level. In the protologue of C. piliventris Saunders 1868b does describe the elytra as red, however, he states that the pre-medial mark is reduced to 'a triangular spot on the suture' (as in C. keyzeri). In the account of Barker 2006a the elytra are still given as red, but the premedial fascia is described as entire or only partly reduced ('may be broken into three spots, one on each elytron and on suture'), and the illustration shows an individual with an entire premedial fascia.

For C. piliventris, Saunders states 'Hab.: Queensland', implying type material from eastern Australia, but according to the AFD there are also syntypes from Adelaide. Eastern Australian specimens referred to C. piliventris in a private collection have the elytra variable in colour from red and orange to almost yellow, in various combinations with their fasciae ranging from complete to interrupted or much reduced. There is also much variation in overall size, and in colouration of the scutellum, pronotum and other parts with bronze to blue reflections.

Barker 2005 compared his new species to C. vanderwoudeae, but the main difficulty, however, is in separating it from C. piliventris.