On your timeline you would place the first colonial organisms at 233 million years BCE. "BCE" means "before common era", and is how we represent in scientific terms how long ago something happened. Colonial organisms are a step in the evolution from single-celled to multi-cellular organisms. A colonial organism is defined as a
collection of genetically identical cells that are permanently associated but in which little or no integration of cell activities occurs.
In other words, colonial organisms are made of cells that are formed from the same, individual cell, and live together permanently, but do not have any specialization of function the way cells do in multi-cellular organisms. Green algae are thought to be the first example of this type of organization; some still exhibit this type. The steps from single- to multi-cellular organisms is believed to be:
- cells secreted proteins and sugars that "stuck" them together.
- cell division began to be controlled genetically for these cells, rather than the cells simply reproducing when conditions were favorable.
- some types began to orient their flagella in the same direction, enabling movement of the colonial organism as a whole.
- some specialization of cells occurred for reproduction.
It took about 125 million years for these steps to occur. Development of multi-cellular organisms from single-celled organisms is one of the most important steps in evolution.
After answering your question I came across this new piece of information that may be helpful to you. An article in MSN.com/Technology discusses the likelihood that one particular mutation in a protein may have been the spark that allowed cells to interact and communicate with each other. I've attached the link below. It sounds like much more work needs to be done to confirm that this is a mechanism for allowing cells to work together, but it is quite interesting.