Dragoons historically weren't dismounted cavalry, they were mounted infantry, and equipped accordingly. Gunpowder weapons had enough of a kick that a full infantry musket or rifle would dismount a cavalry man even if the horse was stationary, never mind when moving. Cavalry weapons were notably shorter, and it was very common for the actual cavalry of the era to instead be equipped with a brace of pistols and sabers, or lances and sabers, to break enemy lines and rush through.
What the appropriate term is for space/ground forces is kind of difficult to determine because there's two major factors at play. First, all terrain you are likely to engage in is directly the 'shore line', because from space the question is only how much atmosphere you have to go through, and that's not a question whose answer substantially changes wherever you are on the planet. Second, planets are rather big and come with a lot of different terrain types that on the ground offer different challenges, and it's just not efficient to train for all possible terrain types with all formations. As such, it'd be expected that a formation trains and is equipped to perform extremely well under some circumstances, perform adequately under more circumstances and perform extremely poorly for those circumstances its training and equipment are utterly unsuited for.