Mastodon rhymes with:
sandon, anton, arabichon, arabicon, avignon, bygone, cabletron, chemlawn, cinnabon, coupon, fair-lawn, fairlawn, kingon, kulon, mahlon, marienbonn, regeneron, roselawn, sandon, saskatchewan, schiferon, skylawn, woebegone
Mastodon sounds like:
macadam, macadamia, macedonia, macedonian, mactan, magadan, magten, maktoum, mangosteen, masden, masten, mastin, maston, maxton, mcadam, mccadden, mccuistion, mccuiston, mchatton, mckeithan, mckeithen, mckethan, mcquiston, meston, micatin, minnesotan, moisten, moonstone, mostyn, mujahadeen, mujahedeen, mujahideen, muscatine, mustain, mustin, muston