Couldn't find unit description for unit type 'Champion Marauders'.

During the AI turn on my current Averland campaign, immediately after an AI army moves, my game crashes. The log file indicates:

17:45:59.383 [data.invalid] [error] World creation error: couldn't find unit description for unit type 'Champion Marauders'.
17:45:59.896 [system.rpt] [error] Unspecified error. The game will now exit.

I don't remember any 'champion marauders' and there is no reference to them in the EDU. Do I need to add their description in somewhere?

This seems like it should be easy to fix, I'm just not sure exactly how. Any help?