Eusuchia is a clade

Clade

A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...

 of crocodylomorph

Crocodylomorpha

The Crocodylomorpha are an important group of archosaurs that include the crocodilians and their extinct relatives.During Mesozoic and early Tertiary times the Crocodylomorpha were far more diverse than they are now. Triassic forms were small, lightly built, active terrestrial animals. These were...

s that first appears in the Early Cretaceous

Early Cretaceous

The Early Cretaceous or the Lower Cretaceous , is the earlier or lower of the two major divisions of the Cretaceous...

 with Hylaeochampsa

Hylaeochampsa

Hylaeochampsa is an extinct genus of eusuchian crocodylomorph. It is known only from a partial skull recovered from Barremian-age rocks of the Lower Cretaceous Vectis Formation of the Isle of Wight. This skull, BMNH R 177, is short and wide, with a eusuchian-like palate and inferred enlarged...

. All living crocodilian species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 are eusuchians, as are many extinct forms.

Description

Unlike primitive crocodylomorphs, crocodyliforms have a secondary bony palate. This feature enables living crocodylians to safely breathe in through their nostrils while the rest of the head (including the mouth) remains submerged. This structure reaches its greatest elaboration among eusuchians, in whom the internal nares are completely surrounded by the pterygoid bones.

Phylogeny

Cladogram

Cladogram

A cladogram is a diagram used in cladistics which shows ancestral relations between organisms, to represent the evolutionary tree of life. Although traditionally such cladograms were generated largely on the basis of morphological characters, DNA and RNA sequencing data and computational...

 after Pol, Turner and Norell, 2009:
Below is a cladogram after Puértolas, Canudo and Cruzado-Caballero, 2011: