The Earliest-Known Stem  Mammals

DESCRIBER    Sigogneau-Russell, 1983
TIME    Triassic Late
Rhaetian
CLASS    Mammalia
SUBCLASS    Incertae Sedis
ORDER    Morganucodonta (Kermack, et al., 1973)
FAMILY    Megazostrodontidae (Gow, 1986)
FOSSILSITE    Keuper Formation, Saint-Nicolas-de-Port, Lorraine, France
INFO

Brachyzostrodon coupatezi (Sigogneau-Russell, 1983 ) > Brachyzostrodon major (Hahn et al., 1991)  > Brachyzostrodon sp. (Hahn et al., 1991) > Brachyzostrodon sp. (Jenkins et al., 1994 )

All species of Brachyzostrodon are distinctly larger than any other species of Morganucodon, Erythrotherium and Megazostrodon.