On the basis of new collections from the Lanongla area, Nyalam county, Tibet, Rhaetian and Hettangian ammonoid assemblages are recognized, including the Choristoceras marshi, Neophyllites-Charistoceras, Psiloceras calliphyllum and Discamphiceras pleuronotum assemblages. As the only Triassic and Jurassic boundary section known in the East Tethys, the Germig section provides a biochronological correlation in term of ammonoid assemblage, or zonation in the Tethyan domain; the Choristoceras marshi assemblage is comparable with the MARSHI, or CRICKMAYI Zones of Europe, Peru and Chile, Nevada, British Columbia. Neophyllites and Chorstoceras co-occur in a transitional interval between the Choristoceras marshi and Psiloceras calliphyllum assemblages, which can be likely comparable with that in Nevada of North America where both Neophyllites and Choristoceras appear in the basal Jurassic TILMANNI Zone. The Psiloceras calliphyllum assemblage is most likely equivalent to the CALLIPHYLLUM Zone of North Alps and the PLANORBIS Subzone of Northwest European Province.