Wilson, Don E.; Reeder, DeeAnn M. (16 November 2005). Mammal Species of the World: A Taxonomic and Geographic Reference. JHU Press. ISBN 978-0801882210 . Retrieved 20 July 2013. Riedelsheimer, B., Unterberger, P., Künzle, H. and U. Welsch. 2007. Histological study of the cloacal region and associated structures in the hedgehog tenrec Echinops telfairi. Mammalian Biology 72(6): 330-341. The most common form of genital alteration is circumcision, the removal of part or all of the foreskin for various cultural, religious, and more rarely medical reasons. There is controversy surrounding circumcision. Most animals have their reproductive organs located close to their tail-ends. But that's not the case for a newly discovered species of river fish identified in Vietnam's Mekong Delta. Phallostethus culling's penis sprouts, oddly enough, out of its head. More specifically, the reproductive organ shoots out from just under the fish's throat, giving the fish the unique ability to grab onto a female with its mouth while fertilizing her eggs at the same time.

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Rose, Kenneth D.; Archibald, J. David (22 February 2005). The Rise of Placental Mammals: Origins and Relationships of the Major Extant Clades. JHU Press. ISBN 978-0-8018-8022-3 . Retrieved 22 July 2013. McBane, Susan (2001). Modern Horse Breeding: A Guide for Owners. Globe Pequot Press. ISBN 978-1-58574-389-6. Archived from the original on 7 July 2014 . Retrieved 18 February 2014. Lukefahr, Steven D.; Cheeke, Peter R.; Patton, Nephi M. (2013). Rabbit Production. CABI. ISBN 978-1-78064-012-9 . Retrieved 20 July 2013. Dolphins don’t just use their penises for baby-making, either. Bottlenose dolphins frequently copulate for pleasure, and often with members of the same sex. Dolphin sex doesn’t last long, only about ten seconds, but males can ejaculate multiple times an hour. Fencing With a PhallusThe penises of even-toed ungulates are curved in an S-shape when not erect. [20] In bulls, rams and boars, the sigmoid flexure of the penis straightens out during erection. [21] Lienhard, Charles; Oliveira do Carmo, Thais; Lopes Ferreira, Rodrigo (2010). "A new genus of Sensitibillini from Brazilian caves (Psocodea: 'Psocoptera': Prionoglarididae)". Revue Suisse de Zoologie. 117 (4): 611–635. doi: 10.5962/bhl.part.117600. ISSN 0035-418X. Archived from the original on 2014-11-03.