Chicken
Gallus gallus domesticus
No penis to measure.
Doesn't have one
A chicken embryo starts to grow a phallus, but a Bmp4 signal makes its cells die off. Adult roosters mate by pressing their vent to the hen's.
Margin note: Card intentionally left blank.
Sources
- Coles B.H. (2009) Galliformes. In Tully T.N., Dorrestein G.M., Jones A.K. (eds) Handbook of Avian Medicine, 2nd edn. Saunders/Elsevier doi:10.1016/B978-0-7020-2874-8.00013-4
- Clark M.I. (2018) Management of breeding in small poultry production units. In Noakes D.E., Parkinson T.J., England G.C.W. (eds) Veterinary Reproduction and Obstetrics, 10th edn, ch. 30. Elsevier doi:10.1016/B978-0-7020-7233-8.00030-6
- Herrera A.M., Shuster S.G., Perriton C.L., Cohn M.J. (2013) Developmental basis of phallus reduction during bird evolution. Current Biology 23(12):1065–1074 doi:10.1016/j.cub.2013.04.062
- Assersohn K., Brekke P., Hemmings N. (2021) Physiological factors influencing female fertility in birds. Royal Society Open Science 8:202274 doi:10.1098/rsos.202274
- Brennan P.L.R., Prum R.O., McCracken K.G., Sorenson M.D., Wilson R.E., Birkhead T.R. (2007) Coevolution of male and female genital morphology in waterfowl. PLoS ONE 2(5): e418 doi:10.1371/journal.pone.0000418
Drawn from
- Clark 2018, Veterinary Reproduction and Obstetrics, Fig. 30.7: Diagram of a cockerel's reproductive tract ending in the cloaca (coprodeum, urodeum, proctodeum) and vent, with no external phallus