''Oesia disjuncta'' is a monospecific genus known from the Middle Cambrian Burgess Shale. 1147 specimens of ''Oesia'' are known from the Greater Phyllopod bed, where they comprise 2.18% of the community.
Despite some similarities to the chaetognaths, its affinity is unknown, though recent data suggest it may be affiliated with hemichordates.
References
Burgess Shale fossils
Enigmatic prehistoric animal genera
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Cambrian genus extinctions