Well preserved Precambrian algal microfossils and megafossils have been recovered in the northern Mackenzie Mountains from several levels and localities in a basinal, limestone-dominated rhythmite formation of the Little Dal Group. The microbiota includes the filaments Archaeotrichion, Taeniatum and Siphonophycus, and the sphaeromorph acritarchs Kildinella, Trachysphaeridium, Nucellosphaeridium, and Chuaria circularis. The megafossils, ail of probable algal affinities, comprise large carbonaceous ribbons assigned to the new vendotaenid species Tawuia dalensis n.g. n. sp., and the irregular compressions Mariana? antiqua and Beltina danai. The same formation has also yielded a dubiofossil probably representing traces on bedding planes made by small cylindrical, discoid, or spheroidal organisms, questionably referred toBergaueria. The biota suggests a late Helikian to early Hadrynian age (1.1–0.8 Ga) for the Little Dal Group, and adds to the growing body of evidence for the existence of eucaryotic organisms at that time.