The gene set for Platypus was built using a modified version of the standard Ensembl genebuild pipeline, using available cDNA evidence to add UTRs and improve the protein-based gene models. However, this initial geneset was limited by the lack of species-specific evidence. The gene models were assessed by generating sets of potential orthologs to genes from other mammalian species and chicken. Potentially missing predictions and partial gene predictions were identified by examining the orthologs, and exonerate was to align orthologous human and chicken peptides in order to build new gene models. We have now extended the initial gene set using recently released cDNA data from 454 sequencing, plus additional annotation from the Oxford Functional Genomics group. These data have enabled us both to clarify existing models and to add additional transcripts.