from a mainstream paper:
Why sex chromosomes turn over and remain undifferentiated in some taxa, whereas they degenerate in others, is still an area of ongoing research. The recurrent occurrence of homologous and homomorphic sex chromosomes in distantly related taxa suggests their independent evolution or continued recombination since their first emergence.
Here, we focus on sex chromosome evolution in haplochromines, the most species-rich lineage of cichlid fishes…
… we did not find evidence for shared ancestry, suggesting that LG7 evolved as sex chromosome at least twice in haplochromine cichlids. Hence, our work provides further evidence for the labile nature of sex determination in fishes and supports the hypothesis that the same genomic regions can repeatedly and rapidly be recruited as sex chromosomes in more distantly related lineages.