Many of this writer's generation grew up calling everything that had a rotating house that wasn't a crane, a shovel, sometimes even a 'steam shovel' though diesel engines have long replaced steam boilers. While there is actually a page for a real shovel on this site Link Belt LS98 Shovel
Actually machines such as the UH16 are properly called excavators, because the digging boom is configured to dig on the pull stroke (towards the marchine) instead of away from the machine as is the case with a shovel. Coincidently, if you look elsewhere on this site for "log loaders' you will find that they look very similar, and though often called 'shovels', they are in fact modified excavators with different booms and sometimes an elevated cab. Indeed our American 35 is listed in both places as we converted it back to an exavator.
Actually, however, the Excavtors have evolved a lot over the years. As the Cable based track machines were dominantly of USA orgin, the early excavtors were similarly souced. Many models to varying degrees were simply cable machines converted to hydraulics. They would have hydraulic motors instead of friction drives. Classic of these conversions is the Koehring 366 mentions above.
During the recession of 1980, the US manufacturers mostly failed and the Japanese and other far Eastern imports became the order of the Day. Many Hitachi's are sold as John Deere, while Cat has often used another imported brand private labeled.
What the Imported ones did is to start with a pretty much clean slate in their design. Instead of using the old pin and pad tracks of heavy cranes (which wear out quickly ifyou drive them a lot, they used readily available bulldozer undercarriages (usually D-7 Cat compatible). From a design stand point they starded not with a deck designed to hold winches and the like, but just a flat deck. They put a well regarded Japanese engine and used a high pressure hydraulic system. By going to 4 or 5,000 PSI, they could put drive motors inisde planatary reductions for the drive getting rid of the gear trains and drive chains. With piloted hydraulics, the spool valves could be positioned to be optimized for plumbing instead of being optimized for the connection of control levers. Later versions use electic spool valves making all the controls push buttons electric joysticks meaning that only a wiring harness needs to reach the cab.
Alas, This Hitachi is a very early imported machine. It relies on hydrualic piloted hydraulics and highpressure hydraulics, but uses hydraulic pilots for the spool valves.