In the Journal of Molecular Endocrinolgy (Vol 52. No 3) there are several reviews on the evolution of G-protein coupled receptors: Secretin, CRH, Kisspeptin, Ghrelin, melanocortin, somatostatin/urotesin, and the 26 RFamide (GPR103). These reviews are obviously freely available.

I read them only cursory, however, I found very interesting relations of CRH from vertebrates, and diuretic hormones of insects which are going into the English version of the textbook on endocrinology.