Hello your Tetraulax is probably the species gracilis Breuning 1937. Indeed the apex of the elytra stretched in point is rather characteristic. The patterns in Tetraulax can often vary. That's it! I have 3 exes of RSA and Malawi almost identical to this one!
Hi, thanks Jérôme. Indeed, I also have a series of this (males & females), and it seems that the patterns are amazingly constant. Agree that it is most probably T. gracilis although I have not seen the type.