The messaoudensis-trifidum acritarch assemblage (Ordovician: Late Tremadoc - Early Arenig) of the Barriga Shale Formation, Sierra Morena (southwest Spain).
Reference:
Servais,T. et al. (2000)
The messaoudensis-trifidum acritarch assemblage (Ordovician: Late Tremadoc - Early Arenig) of the Barriga Shale Formation, Sierra Morena (southwest Spain). Review of Palaeobotany and Palynology
Vol. 113 # 3 P. 145- 164