- Athabascaella penika
- Athabascaella playfordii
- Athabascaella rara
- Athabascaella rossii
- Athabascaella sp
- Athabascaella sp.A
- Athabascaella sp.A Yin,1995
- Athabascaella sunwaptana
- Atheotesta elliptica
- Athigmatocysta
- Athigmatocysta glabra
- Athigmatocysta granulata
- Athigmatocysta sp
- Athigmatosphaera
- Athleta japonica
- Athyrium sp.1
- Athyrium sp.2
- Athyrium sp.3
- Atiemia sp
- Atlantodinium
- Atlantodinium jurassicum
- Atlantodinium sp.A Bren.,1992
- Atlantodinium sp.A Poul.,1996
- Atlantopollis
- Atlantopollis choffatii
- Atlantopollis convexus
- Atlantopollis grootii
- Atlantopollis heystii
- Atlantopollis lusitanicus
- Atlantopollis microreticulatus