The members of the order Pasteurellales are currently distinguished mainly based on their position in the branching of the 16srRNA tree. There are currently very few molecular markers known that can distinguish members of this order from other bacteria. A CSI approach was recently used to elucidate the phylogenetic relationships between the species in this order; more than 40 CSIs were discovered that were uniquely shared by all or most of the species. Two major clades are formed within this Pasteurellales: Clade I, encompassing Aggregatibacter, Pasteurella, Actinobacillus succinogenes, Mannheimia succiniciproducens, Haemophilus influenzae and Haemophilus somnus, was supported by 13 CSIs. Clade II, encompassing Actinobacillus pleuropneumoniae, Actinobacillus minor, Haemophilus ducreyi, Mannheimia haemolytica and Haemophilus parasuis, was supported by 9 CSIs. Based on these results, it was proposed that Pasteurellales be divided from its current one family into two different ones. Additionally, the signatures described would provide novel means of identifying undiscovered Pasteurellales species.