ECL and CR have nothing to do with each other. ECL is a measure of how likely a creature is to grab the limelight as a PC. CR is a measure of how tough it is for a party to kill.
A lizardfolk ari1 would have a CR of 1, as I recall.
ECL and CR are completely seperate. Even though he has a +4 ECL, a Lizardfolk still has a CR of 1. The PC's CR is 1 (actually 1.5). NPC classes add 1/2 CR per level, which is rounded down.