Diogenes and the "Platonic human"

According to the ancient biographer Diogenes Laertius, Plato was praised for defining a human as a featherless biped. Diogenes of Sinope brought in a plucked bird and joked, “Here is Plato’s man.” The detail that the Academy then added “with broad, flat nails” appears in later retellings; this is a witty anecdote, not a transcript of an event.