Penis
primary sexual organ of male animals
In many animals, a penis (; pl.: penises or penes) is the male sexual organ used to inseminate females (or hermaphrodites) during copulation. Such organs occur in both vertebrates and invertebrates, but males do not bear a penis in every animal species. Furthermore, penises are not necessarily homologous.
The term penis applies to many intromittent organs, but not to all. As an example, the intromittent organ of most Cephalopoda is the hectocotylus, a specialized arm, and male spiders use their pedipalps. Even within the Vertebrata, there are morphological variants with specific terminology, such as hemipenes.
In most species of animals in which there is an organ that might be described as a penis, it has no major function other than intromission, or at least conveying the sperm to the female, but in the placental mammals, the penis bears the distal part of the urethra, which discharges both urine during urination and semen during copulation.
Vertebrates
The last common ancestor of all living amniotes (mammals, birds and reptiles) likely possessed a penis, and it has been suggested that the penises of living amniotes are likely homologous to each other and share a common developmental origin.
Birds
Most male birds (e.g., roosters and turkeys) have a cloaca (also present on the female), but not a penis. Among bird species with a penis are paleognathes (tinamous and ratites) and Anatidae (ducks, geese and swans).
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The citation trail is more important than the brevity of the summary: it shows where individual claims can be examined in context. The source revision retrieved here is dated Sep 15, 2026. The linked authority identifier is Q58. The Library of Congress control number is sh85099480. 1 of 1 selected statements include explicit references; 1 carry qualifiers and 0 use preferred rank.
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This entry incorporates text from “Penis” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.