When Mark was an epitome of Matthew

The "Gospel of the Ebionites" is associated with Jewish-Christian sects and - by Epiphanius - with Cerinth the haersiarch. Wilhelm Schneemelcher (d. 1928) thought it was a stripped-down Matthew, and that's the last word at Wikipedia. Here, I would muse upon Epiphanius and his Panarion.

It happens the Panarion has suffered by interpolation. It enjoyed great popularity: it was adapted by many, not least John Damascene. Its standalone text itself got glossed on its way to mediaeval times. A few days ago Richard Carrier raised flags about how this text handled the Library of Alexandria.

I know of one gospel as of the late second century dismissed as the truncation of Matthew - our gospel of Mark, as in fact Augustine and his Church would remember it. During this Marcan darkage, Hippolytus of Rome preceded Epiphanius as a refuter of all haeresies. As Mark struggled back into canon, those haeretics still using Mark might not be accepted as using Mark, instead using something spurious (like "Peter" is spurious). Maybe Clement of Alexandria could get wind of a "secret Mark" as was not Matthew; but he was writing later than Hippolytus, and was more intelligent than was Epiphanius.

So these Mark-using haeretics were first blamed for using truncated-Matthew, in second-century haeresiologies; subsequently parroted in Epiphanius and various glossers, who knew Mark but didn't remember Mark's time on the outs.