Dassault Mercure
 

Anybody know why the Mercure had such a pronounced tailplane dihedral compared to the A320 to which it otherwise bears more than a passing resemblance?
I thought not.

Following found at: http://yarchive.net/air/airliners/727_rear_doors.html

As to why the Mercure looks so much like the A320 - yes it is
related and no, it isn't. The Mercure was built by Dassault, which is a (nominally) private French aero company, while Aerospatiale, which is part of Airbus is the publicly held French aero company. Back in the gestation of the A320, Dassault was involved in one partnership which looked at a growth Mercure with CFM-56s. This partnership split, but begat other partnerships that lead to the A320. You might say that the growth Mercure genetically led to the A320. On the other hand, Dassault was not involved (directly) in the design of the A320, so any relationship is distant.

I also found a picture of a mock-up at:
http://translate.google.com/translat...%3Den%26sa%3DN

It shows no tailplane dihedral, so presumably they built it, it flew like a dog, they fixed it.