However, these seem to have been more closely related to modern birds than to Ichthyornis dispar. In Julia Clarke's 2004 review of Ichthyornis-like fossils, the former order Ichthyornithiformes and the family Ichthyornithidae were considered synonyms of the clade Ichthyornithes, which in that paper was defined according to phylogenetic taxonomy as all descendants of the most recent common ancestor of Ichthyornis dispar and modern birds.
The fossils were found to be more closely related to modern birds than to Ichthyornis dispar.  Julia Clarke's 2004 review suggested that Ichthyornithiformes and Ichthyornithidae, which are now considered synonymous with the clade Ichthyornithes, should be defined based on their phylogenetic relationship to the most recent common ancestor of Ichthyornis dispar and modern birds.