No, the iPad Mini is just the iPad Mini. The 4th gen iPad was updated at the time the Mini came out to give it the same new dock connector and boosted specs, probably to prevent people from flooding to the cheaper option due to the perceived outdatedness of the larger iPad.

I don't know why they didn't stick with just iPad 3 and iPad 4. Maybe people have different reactions to version numbers?

In any case: The third-generation iPad ("The new iPad") was released last Spring. The fourth-generation iPad ("iPad with Retina Display") was released last Autumn. The iPad Minis internally have the same major version number at the iPad 2s. There isn't much difference between the third and fourth generations, other than a new port and a slight spec bump.

Wait, the newest one (the second version to have Retina) is "iPad with Retina Display"? Are you sure those aren't backwards? Because that'd make no sense to me.

Yeah, that's the right way round. Crazy, huh? The only reason I can think of is to have parity with the "MacBook Pro with Retina Display".

Thunderbolt. When the iPad Mini was announced, they announced the new iPad (regular) would have a Thunderbolt port, which put them at 4th gen.

Apple call it a "lightning" connector, and I don't think its mechanicalally or electrically compatible with the Thunderbolt port... I think it even connects to bog standard USB 2.0

You mean "Lighting connector"?

You mean lightning connector.

Lightning, not thunderbolt.

The biggest hardware improvement is the inclusion of the Apple A6X processor. The third generation iPad had the A5X.

The iPad 4 also has the A6X processor compared to the A5X in the iPad 3.

iPad 3rd gen was released in March with retina. iPad 4th gen was released in November (alongside the mini) and added a Lightning connector.