Dear colleagues, I am pleased to announce our new paper which can be found at https://royalsocietypublishing.org/doi/10.1098/rspb.2024.1106 Telizhenko V, Kosiol C, McGowen MR, Gol'din P. 2024 Relaxed selection in evolution of genes regulating limb development gives clue to variation in forelimb morphology of cetaceans and other mammals. Proc. R. Soc. B 291: 20241106. https://doi.org/10.1098/rspb.2024.1106 <https://doi.org/10.1098/rspb.2024.1106?fbclid=IwZXh0bgNhZW0CMTAAAR3MBTpJmPW1IYq5OFfQdqSuqjiqhvklVmGXzuxiZARco0LnkimwWS4eRCs_aem_AGMgQP7sVnkrubYr1LcP9w> Cetaceans have evolved unique limb structures, such as flippers, due to genetic changes during their transition to aquatic life. However, the full understanding of the genetic and evolutionary mechanisms behind these changes is still developing. By examining 25 limb-related protein-coding genes across various mammalian species, we compared genetic changes between aquatic mammals, like whales, and other mammals with unique limb structures such as bats, rodents and elephants. Our findings revealed significant modifications in limb-related genes, including variations in the Hox, GDF5 and Evx genes. Notably, a relaxed selection in several key genes was observed, suggesting a lifting of developmental constraints, which might have facilitated the emergence of morphological innovations in cetacean limb morphology. We also uncovered non-synonymous changes, insertions and deletions in these genes, particularly in the polyalanine tract of HOXD13, which are distinctive to cetaceans or convergent with other aquatic mammals. These genetic variations correlated with the diverse and specialized limb structures observed in cetaceans, indicating a complex interplay of relaxed selection and specific mutations in mammalian limb evolution. Feel free to contact authors, including Valeriia Telizhenko valeriia.dccclxiv@gmail.com On behalf of the team and all the best, Pavel Gol'din, Schmalhausen Institute of Zoology, Kyiv, Ukraine