ayellowbirds:

lionesses that grow manes and lions that don’t
fish and amphibians that change reproductive sex depending on age, environment, or availability of mate
an entire species where the vulva and clitoris adapted into an organ outwardly indistinguishable from a penis, complete with a scrotum—spotted hyenas
some bears who show that as a mutation, including individuals known to have given birth
countless documented cases of same-sex partnerships in animals that mate for life
insects where the semen-bearing sex is the one that receives penetration and the ova-bearing sex is the one that has a penetrative phallus
seahorses, my gods, you should know about seahorses by now
“male” cuttlefish that present as female and seek to mate with other females
countless species where the larger, more aggressive sex is female and the smaller, flashier one is male

but for your science fiction or fantasy setting, you decided that most nonhuman sapients have a strict gender binary that maps perfectly to contemporary western human cultural standards?

even humans aren’t like that.