The bill skin of the platypus and echidna detects tactile stimulation via the push-rod, thought to be a type of mechanoreceptor.
"The other prominent receptor in the bill skin of both the platypus and echidna is the 'pushrod,' which is thought to be a mechanoreceptor responding to tactile stimulation." (Fowler and Miller 2003:279)
Learn more about this functional adaptation.
- Fowler, ME; Miller, RE. 2003. Zoo and Wild Animal Medicine. Philadelphia: W.B. Saunders Co.