KHDRBS protein sequences of most major metazoan taxa were obtained from NCBI and Ensembl database. Other KHDRBS protein sequences were identified by a BLASTp search with a query sequence (human KHDRBS1 protein). The sequences used were listed in Supplementary Table 1. Sequence alignment was performed by ClustalW method in MegAlign v7.1.0. To acquire the best evolutionary model for phylogenetic inference, we used default parameters in MEGA7 to conduct a best-fit protein model test. According to calculated BIC (Bayesian information criterion) scores for every model, we chose LG + G model which had the lowest score for further phylogenetic analysis. After that, rooted phylogenetic trees were constructed by Bayesian analysis and maximum likelihood (ML) method. These two methods were conducted with MrBayes v3.2.6 and PHyML website, respectively. ML phylogenetic analysis used LG + G model and set bootstrap as 1,000 replicates. Bayesian analysis was performed with following parameters: ngen = 2,000,000, nruns = 2, nchains = 4, aamodel = fixed (LG), rates = gamma, samplefreq = 1,000, burninfrac = 0.25. Finally, phylogenetic trees obtained were viewed and modified with FigTree v1.4.2. Synteny data of khdrbs genes were collected using tools available from Ensembl and NCBI database. Gene structural features of those chosen transcripts were analyzed using data from Ensembl database. Characteristics of the protein domain were predicted by SMART website.