Liassic ammonites from the Nong Son basin are rare, and little diversified.
The fossil record is restricted to two fossiliferous beds. The ammonites d
isplay original features with the genera Ectocentrites CE. dommerguesi nov,
sp. et E. kherucensis nov. sp.) et Tongdzuyites nov. gen. (T. nongsonensis
nov, sp.). These new ammonites are with difficulty correlatable with forms
in the literature and moreover their age is not precise; it includes an in
terval of uncertainty from Early Sinemurian to Early Pliensbachian. For the
first time Atractites, associated with the ammonites, is recorded from the
Nong Son basin. Worldwide correlations are attempted between the Vietnames
e fauna and related taxa.