It is quite common for a Lizardmen army to include units containing models with different sized bases such as a Slann in a Temple Guard unit or one or more Kroxigor in a Skink unit - so it is worth some clarification as to how this affects ranks and rank bonuses.

The best way to handle rank bonuses is to count the model on the larger base as the same number of models that would normally occupy that space. So, a Slann in a Temple Guard unit would count as four models two in each rank - when determining rank bonus (see example diagram below).

Furthermore, by the normal Warhammer rules, a rear rank cannot be larger than the one in front. Following the above principle, if there were two Kroxigors in a unit of Skinks, and only three Skinks were left in the front rank, one of the Kroxigor would have to move forward to the front rank.