This list of the Mesozoic life of South Dakota contains the various prehistoric life-forms whose fossilized remains have been reported from within the US state of South Dakota and are between 252.17 and 66 million years of age.
A
Acipenser – or unidentified comparable form
†Actinocamax
†Actinosepia
†Actinosepia canadensis
†Adocus
†Agerostrea
†Agerostrea translucida
†Aletridelphys
†Aletridelphys florencae
†Aletridelphys hatcheri
†Allosaurus
†Alphadon
†Alphadon marshi
†Amesoneuron
†Amesoneuron FU37 – informal
†Anatotitan
†Anatotitan copei
†Anisomyon
†Anomia
†Anomia gryphorhyncha
†Antillocaprina
†Anzu – type locality for genus
†Anzu wyliei – type locality for species
†Apatosaurus
†Araucarioxylon
†Araucarioxylon hoppertonae – type locality for species
†Archelon – type locality for genus
†Archelon ischryos
†Archelon ischyros – type locality for species
†Artocarpus – report made of unidentified related form or using admittedly obsolete nomenclature †Artocarpus lessigiana Aspideretes †Asplenium †Asplenium Dicksonianum †Axestemys – or unidentified comparable form †Axestemys splendida