The Inferno Canto XXV

Vanni Fucci concludes his spiteful predictions by blaspheming with an obscene gesture. The serpents immediately engulf him, and Dante considers them as friends from that time forth. A centaur approaches whose haunches are covered with snakes and upon his shoulders a dragon rests. He is Cacus, a mythological monster known for thievery. Then Dante sees five of noblemen of Florence: Agnello, Buoso, and Puccio who are in human form; and Cianfra and Francesco de' Cavalcanti, who are in reptile form. Dante witnesses the reptilian Cianfra merged with the body of Agnello followed by a bizarre exchange of form between Buoso and Francesco.