Symmetrodonta, Simpson, 1925

O. Averianov, Alexander, 2002, Early Cretaceous “ symmetrodont ” mammal Gobiotheriodon from Mongolia and the classification of “ Symmetrodonta ”, Acta Palaeontologica Polonica 47 (4), pp. 705-716 : 714

“ Symmetrodonta ”

Though I do not ascribe to the view that a classification must be isomorphic with a single cladogram, a classification must clearly not contradict the prevailing phylogenetic hypothesis (e.g., Fox 1985: 24; Sigogneau−Russell and Ensom 1998: 455).In the case of “symmetrodonts”, available data are ex − tremely scarce and limited, so that a reliable, robust hypothesis of relationships is presently unattainable.Among “sym − metrodonts”, a reasonably well−corroborated phylogeny can only be established for the specialized spalacotheriids; the relationships of the remaining taxa remain problematic.In this case a conventional classification, based on some degree of similarity between taxa, appears to be the most reasonable and stable approach.As discussed above, monophyly of a broadly conceived “ Symmetrodonta ” is poorly corroborated and has been contradicted by recent studies: while continuing to use the group name mainly for the purposes of convenience, I tend to agree with other authors who consider this group as paraphyletic, if not polyphyletic (see review by Luo et al.2002).The classification of “ Symmetrodonta ” pro − posed herein is presented in Table 1.