Who were the Antidicomarites?

[Pergamum]

"Heretics called Antidicomarites are those who contradict the perpetual virginity of Mary and affirm that after Christ was born she was joined as one with her husband"

Augustine, Heresies, 56.


Why would denying the perpetual virignity of Mary be considered a "heresy" and not merely a minor error?

Did the Catholic Church count this as an excommunicatable offense?

 

[Douglas P.]

Antidicomarites (Antidicomarita; lit. "litigant against Mary"). Who are they? I guess I would be one.

If you google Antidicomarites you'll get hand-full of books which speak on the issue, but after a quick scan I can't tell if any of them get into the history of how the Catholic Church dealt/deals with them.