Claim: Megistotherium—an extinct genus of hyaenodontid that is possibly a junior synonym of Hyainailouros sulzeri—had a carnassial teeth that were the upper first molars which overlapped with their lower counterparts in which these can be used for their ample supply of prey from the bodies of water.
Evidence: Megistotherium (from Greek, megistos "greatest" + therion "beast" and osteon 'bone' + thlaston 'crushed, bruised' with -es being an agent noun: 'bone-crusher') is an extinct genus of hyaenodontid, the only known species of which is Megistotherium osteothlastes. It is possibly a junior synonym of Hyainailouros sulzeri (see below). The carnassial teeth of Megistotherium (like those of other hyaenodontids) were the upper first molars, and overlapped with their lower molar counterparts like scissors to form a formidable and powerful shearing action. Lakes and ponds provided water for large fauna, which provided Megistotherium and other predators with an ample supply of prey.