Hi, A.D. —
I can only speak for Christ's Church, the Catholic Church.
Before ascending into Heaven, Jesus only founded one Church and said to St. Peter
that the gates of Hell would not prevail against His Church with Peter and his successors
If what you said is true, the Oxford World Christian Encyclopedia is wrong or you are misreading something.
There was one Church back in 33 A.D.; and there is one Church today.
The only thing 242 or 245 could possibly represent are religious orders within the one Church.
These are different ways of living out the Catholic Christian life in accord with today's one Catholic Church.
They are not denominations as the Catholic Church has no denominations.
We are the one Church that Jesus founded on St. Peter and His successors.
Hope this helps,