I just started using Blender, so I don't have much knowledge about its tool and stuff. Anyway, I was trying to animate an object, put the bones and assigned the vertex that wanted, etc. But when I move a bone that moves other bones together, some parts of my mesh stays behind. I checked to see if I have selected some wrong vertex, but nope. I believe it has something to do with loose faces that has no edge and vertex, but I'm not sure and have no idea of how to fix it. If anybody could help, please! I'm desperate! And thanks!
The vertex of those parts that stay behind means you don't have them assigned to any bones to move them. Check all the vertex groups in weight painting mode and most likely they will be blue for all vertex groups.
You can select a vertex group while the mouse pointer is still in the list you can use the up/down arrow key to select all the vertex in the list to check quicker.
Then you need to weight paint them with the Add brush to the desired vertex group.
Select mesh object (e.g. dino) and go to edit mode. Apply selected mesh you want to move, click the Data icon (one with 3-dot triangle icon, highlighted in blue) at the right, go to Vertex Group under Data. Select the bones to assign (e.g. neck) and click assign.
Try move that bone in Pose mode.
Also, you have to be less messy in assigning bones to each of the selected vertex group carefully.