Most phylogenetic studies of the three diadectomorph families – Diadectidae, Limnoscelidae, and Tseajaiidae – have found diadectids and limnoscelids to be more closely related to each other than either is to "Tseajaia". In other words, Diadectidae and Limnoscelidae form a clade within Diadectomorpha and "Tseajaia" is excluded from the clade. In a 2010 phylogenetic analysis, Diadectidae formed a clade that was characterized by wide cheek teeth with cusps on either side. Unlike previous studies, it was found to be more closely related to Tseajaiidae than Limnoscelidae. The family was defined as "Diadectes" and all taxa sharing a more recent common ancestor with "Diadectes" than with "Tseajaia". Below is a cladogram modified from the 2010 analysis: