What is "archelosauria"

Archelosauria is a clade proposed in 2014 for the grouping of turtles and archosaurs (birds and crocodilians) and their fossil relatives. There were about 1000 ultra-conserved elements in their genome that are unique to turtles and archosaurs, but are not found in lepidosaurs (tuatara, lizards and snakes). Other genome-wide analysis also supports this grouping.