The genus considered to be the most basal member of the family.

It is considered to be the most basal member of the group Trionychoidae.

These analyses usually placed it as a basal member of a group called Mesoeucrocodylia.

Thus, they may be quite basal members of the Palacrocoracoidea.

It is the most basal known member of the Parvicursorinae.

According to Paul, ornithomimosaurs are the most basal members of this group.

Genetic studies show it is a basal member (early offshoot) within the group.

It is apparently a basal member of its genus (Rice et al. 2003).

According to a 1997 paper, Callichthys is the most basal member of the subfamily.

An analysis published in 2010 indicated it was a basal member of the Hadrosauroidea.