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Australian researchers discover why only two of echidna's four penis heads become erect at one time | Australia news | The Guardian
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Plasma progesterone secretion during gestation of the captive short-beaked echidna in: Reproduction Volume 162 Issue 4 (2021)
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Nature's strangest SEX rituals, revealed - from echidnas with four-headed penises to banana slugs that can mate with themselves | Daily Mail Online
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Journal de l'anatomie. mesure du museau au cloaque de l'Platypusis 87 cm. et 18 cm de largeur. Ecliidaa {Echidna aculeata). Comme dans l'Ornithorynque, trois grandes parties de la rate peut être
![Australian researchers discover why only two of echidna's four penis heads become erect at one time | Australia news | The Guardian Australian researchers discover why only two of echidna's four penis heads become erect at one time | Australia news | The Guardian](https://i.guim.co.uk/img/media/d3fadd01edc9b19f597c1f7d3638581ac85ee822/0_108_1440_864/master/1440.jpg?width=700&quality=85&auto=format&fit=max&s=ec0910ff8b963e58e9fe6e7e2bb3db9a)
Australian researchers discover why only two of echidna's four penis heads become erect at one time | Australia news | The Guardian
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