These bats are the only mammals known to mate without non penetrative sex - eviltoast
These bats are the only mammals known to mate more like birds
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Male serotine bats have penises too large for penetration. To mate, the animals rub their genitals against each other, somewhat like birds’ cloacal kiss.

This study in serotine bats (Eptesicus serotinus) shows that the penis is used as a ‘copulatory arm’ rather than an intromittent organ, revealing a novel copulatory behaviour in mammals. DOI:https://doi.org/10.1016/j.cub.2023.0