The Mesozoic Sclerorhynchoidea are basal or incertae sedis; they show features of the Rajiformes but have snouts resembling those of sawfishes.
Adrian Hunt and Martin Lockley, who described Entradasuchus in 1995, classified it as Crocodyliformes incertae sedis.
The Cretaceous Mesohemerobius was formerly considered a brown lacewing, but is today rather placed as incertae sedis in the Neuroptera; it might be a member of the Hemerobioidea but not even that is certain.
But paleontologists Richard Butler and Robert Sullivan nonetheless view the species as being Marginocephalia incertae sedis, rejecting the presumed synapomorphies with the Pachycephalosauria as incorrect identifications or lacking cogency because of a possible presence in ceratopsian groups.
Romer considered Younginidae to include many genera that are no longer classified as younginids: Paliguana, Palaegama, and Saurosternon are now considered basal lepidosauromorphs, Galesphyrus and Heleosuchus are diapsids of uncertain affinities (incertae sedis), Heleophilus is now a milleretid, andHeleosaurus is now thought to be a varanopid synapsid.