Can somebody help me... and tell me what this part is called ????

Hello everybody, I was driving along the motorway the other day and something came off from under the bumper area , I drove over it and looking behind saw a long black plastic shape , I couldn't stop so had to leave it.panicking driving to the next service stop thinking it was half my bumper I drove over I got out an was relieved my bumper is fine and still intact,but around the inside of the wheels you can see threw to parts of the engine , and around the inside of both front wheels the plastic guard is missing

Any body any ideas what this is thanks

Thank you for the help guys much appreciated