The “symmetrodont” mammal, Gobiotheriodon infinitus (Trofimov, 1980), from the Early Cretaceous (Aptian–Albian) of Mongolia, is redescribed.The species is restricted to the holotype only (dentary with three last molars), the referred maxillary fragment with M3? is considered here as cf. Gobiconodon sp.The dental formula of G. infinitus is reinterpreted as i1–3 c1 p1–3 m1–4. G. infinitus is characterized by a short dentary symphysis; long, well−developed Meckel's groove; small, triangular−shaped pterygoid fossa; weakly developed pterygoid crest; i3 enlarged; p1–3 two−rooted; lower molars acute− to obtuse−angled, labial cingulids lacking, lingual cingulids very short, well developed mesial and distal cingulid cuspules (“e” and “d”) and prominent wear surface on the paracristid. Gobiotheriodon is similar to Tinodon (Late Jurassic, USA; Early Cretaceous, Great Britain and Portugal) in postcanine dental formula and structure of the pterygoid fossa;it is provisionally assigned to Tinodontidae Marsh, 1887. Some taxa previously assigned to (or suggested as possible relatives of) “Symmetrodonta” are reviewed. Amphidontidae Simpson, 1925 is considered as nomen dubium. A new classification for “Symmetrodonta” is proposed.

Key words: Gobiotheriodon, “Symmetrodonta”, systematics, Höövör, Mongolia, Early Cretaceous.

Alexander O. Averianov [sasha@AA1923.spb.edu], Zoological Institute, Russian Academy of Sciences, Universitetskaya, nab. 1, 199034 Saint Petersburg, Russia.