Historically, all known living and extinct crocodiles were indiscriminately lumped into the order Crocodilia. However, beginning in the late 1980s, many scientists began restricting the order Crocodilia to the living species and close extinct relatives such as Mekosuchus. The various other groups that had previously been known as Crocodilia were renamed Crocodylomorpha and the slightly more restricted Crocodyliformes. Crocodylomorpha has been given the rank of superorder in some 20th and 21st century studies.
The old Crocodilia was subdivided into the suborders:
Eusuchia: true crocodilies (which includes crown-group Crocodylia)
Mesosuchia: 'middle' crocodiles
Thalattosuchia: sea crocodiles
Protosuchia: first crocodiles
Mesosuchia is a paraphyletic group as it does not include eusuchians (which nest within Mesosuchia). Mesoeucrocodylia was the name given to the clade that contains mesosuchians and eusuchians (Whetstone and Whybrow, 1983).