Really bad toy pics, but;
So;
-Humanoid
-Dragon
-Dump Truck
-Dog
-Train
What a thematic group, huh? >_>
Yellow's truck (chest and right arm) and pink's train (all of the legs - white's dog is basically a shin-insert) seem to be make up most of the body.
The main gimmick seems to be the "throne" on the chest, where red's mecha is normally located. Red's machine can swap places with Blue's dragon into what looks like a chimera mode or something >_>;
Aaaand then the first extra mecha;
Paonmaru, an elephant and UFOmaru (take a guess <_<). Each transforms into its own little robot, and then when they combine with Shurikenjin, they take Red's place on the throne.