The Gospel of Mark is believed to have been written several decades before Matthew, Luke & John.
The original manuscript that we have ends abruptly where Chapter 16, verse 8 is. We have found two alternative ending (one referred to as the long ending and one referred to the short ending), but whether there are more to the ending than we currently have, we do not know for sure. The other Gospels mention Jesus doing things after rising from the Dead that might have been in Mark’s Gospel, but that were lost.
Jimmy Akin talked about this last month on Catholic Answers Live in more detail after a woman called in asking about a fiction book she was reading about the missing pages. She thought it might be a silly question, but it turned out to be a very good question. Jimmy is of the belief that there are not other lost pages and that the Gospel of Mark was a literary style of taking notes.
Check your Bible and see if it goes to verse 8 or on to verse 20. And if it has the long, short, or both alternative endings.
Verses 17-20 of Mark’s Gospel are not an optional afterthought, they are part of the Gospel and are included in the Lectionary. These verses speak of the signs and wonders that would be associated with ordinary believers(not only apostles). Check it out!
Right, but what I am saying is in the original manuscript it stopped before these verses. In others that they found, the short and the long version that included these verses were included. There are some who believe there are other missing portions that have been lost. But, yes, we should accept the ones that have been found, even if there are more to the Gospel that is missing or that is non-existent.
I highly recommend this book:
Why Four Gospels? by David Alan Black (amazon.com)
Even though the author is a Baptist, his thesis and research is solid and matches well with the more traditional Catholic understanding that Matthew’s gospel was first, not Mark’s.
Does he give reasons that support this claim? I’m genuinely interested.
Even though he is not Catholic, from what I can remember he relies on early fathers/tradition. Basically, the earlier you get back in history, the more credible the sources.