These fossil taxa cannot be assigned to any major group with reasonable certainty. The "proto-birds" above are of some indeterminate basal position in the entire avialan (and paravian) radiation, but known from such diagnostic material that their relationships at the family level are known. In contrast, the taxa here have a hypodigm that is usually just sufficient for giving them a valid scientific name, but not for phylogenetic purposes beyond classing them as pygostylians or more modern birds. Some, however, are known from such fragmentary remains that the possibility that they are non-avian "reptiles" such as dinosaurs cannot be ruled out at present.