Grimpoteuthis plena is known from only one specimen, which cannot be easily separated from other species of Grimpoteuthis in the Atlantic Ocean. This species may be a senior synonym to Grimpoteuthis wuelkeri (but has fewer suckers), but the poor condition of the only known specimen (the holotype) hinders comparison. Grimpoteuthis plena, along with G. wuelkeri and G. discoveryi, may all be junior synonyms of G. umbellata, but this also cannot be resolved given the poor condition of the only known G. umbellata specimen.

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