It's a bit more than that.
"The last twelve verses of the commonly received text of Mark are absent from the two oldest Greek manuscripts (א and B), from the Old Latin codex Bobiensis (itk), the Sinaitic Syriac manuscript, about one hundred Armenian manuscripts, and the two oldest Georgian manuscripts (written A.D. 897 and A.D. 913). Clement of Alexandria and Origen show no knowledge of the existence of these verses; furthermore Eusebius and Jerome attest that the passage was absent from almost all Greek copies of Mark known to them. The original form of the Eusebian sections (drawn up by Ammonius) makes no provision for numbering sections of the text after 16:8. Not a few manuscripts that contain the passage have scribal notes stating that older Greek copies lack it, and in other witnesses the passage is marked with asterisks or obeli, the conventional signs used by copyists to indicate a spurious addition to a document."
Metzger, B. M., United Bible Societies. (1994). A textual commentary on the Greek New Testament.