It is of uncertain taxonomic placement within the subphylum Chelicerata.

It is of uncertain placement within the order Ericales, and was described in 2001.

It has always been of uncertain placement, in the past usually being submerged in the family Flacourtiaceae.

Prieto-Marquez et al. (2006) found the animal to be a hadrosaurid, but of uncertain placement within the family.

It is of uncertain taxonomic placement within the order Eurypterida.

It is controversial because of its uncertain placement.

Those with a question mark preceding the name have an uncertain placement.

It might form a group with Capsaspora, another opisthokont of uncertain placement.

Some species are of uncertain placement with regard to these groups, however:

Genera with a question mark preceding them have an uncertain taxonomic placement in the family.