Bottom Bracket mounted derailleur
 

OK, just when you think you've seen it all... I haven't really dug into it yet but this Marin Larkspur '98 has a FD mounted to a bracket that appears attached to the BB. I'm not a fan of the crank that came with this bike but I'm seeing several reasons to stay with it. First, this hybrid has a 42t big sprocket and a 24t small. Normally I'd think this is too small for a hybrid but with the 11t freewheel, maybe not. Presumably I'd be able to remove the bracket and go with a low mount clamp derailleur. The mount seems to come with a chain guard that keeps the chain off the BB. This all seems needlessly complicated to me but apparently Marin changed to this FD from the previous years clamp style of the previous year. Can anyone add any words of wisdom to my musings?https://cimg0.ibsrv.net/gimg/bikefor...fe8bd3e431.jpg

I've dealt with a few of those. Their only advantage is ease of bike production. The crank, BB, and FD are a system - slap them on with no need for much tweaking. As you pointed out, a ring change will require replacement.

It's held in place by the BB fixed cup or cartridge. To remove it, you have to first remove crank arms and BB.

E-Type FD, been around for years (although they would have been pretty new back in '98) as Moe Zhoost notes, they're for ease of production and have been superseded mainly by Direct Mount, although less and less MTBs have FD's now.

For a bit more info, see here https://www.bikeradar.com/features/s...nts-explained/