How to handle titles and responsibilities changing separately?

 BLUF: How do I represent on my resume that my title and responsibilities changed at different times?
 
Let me give you a bit of background. I work in IT for a regional Financial Institution. I have been with the System Administration group for over two years working on a small (4 person) team within that larger (25 person) group. About 8 Months ago I was promoted from Associate Sys Admin (level 1) to Sys Admin (level 2). There is also a Senior Sys Admin (level 3) position in the larger group. Everyone in my team is now the level 2 position, I was the newest person and the most recent to be promoted. There was no change in my responsibilities or job functions at this time. I was doing the same work, just making more money for it.
 
5 Months ago, 3 months after the promotion, our department was reorganized when our manager was promoted to a director position. My team and one other team of 4 was split out of the System Administration group. The rest of the Sys Admin group was given to another manager and the 2 teams were set to report directly to the department director. All of her other direct reports are Managers of their groups including the new manager of the System Administration group. She didn't have time to manage 8 new direct reports so she made myself and one person from the other team the 'team leads'. This concept didn't exist before the reorg. We are explicitly not 'managers' but we are responsible for all of the functional components of managing the teams. We assign work, represent our team in projects and meetings, report status and issues to the director, and I am currently leading the effort to hire another member for my team. I have seen this as an opportunity and have implemented, slowly, as many manager tools as I can, starting with One on Ones within weeks of the reorg.
 
So now I'm not sure how to present these changes on my resume. When I was made a 'team lead' my title didn't change. I'm still a Sys Admin like everyone else on my team. Yet my responsibilities are very different from the rest of the team.
 
I think I have two options:
First I can show one 'title change' when I was promoted and just include the new responsibilities in that title, even though I didn't start doing them at the date listed.
 
Second I can show two separate 'positions', one lasting only 3 months and both having the same title but the second having more responsibilities.
 
I am leaning towards the first but I'm really not sure which is 'correct'. I know I need to do something as I'm already behind in my quarterly resume updates.
 
Any input or feedback would be most appreciated.

Canyon R