That part is the timing chain tensioner! There is an aluminum crush washer/sealing ring that exists between the tensioner and the cylinder head, it appears that a crack has developed in the washer/ring from your picture! The washer/ring is only a couple millimeters in cross section dimension and mabye one mm thick.

The tensioner assembly is removed with a 27 mm/1 1/16" socket or wrench applied to the larger of the two hex sections of the assembly, the crush washer/seal ring is available from on line suppliers and at the dealership. Hopefully being that you pulled over and shut down quickly after the oil level warning light illuminated you didn't damage anything. It is amazing how quickly 7-8 quarts of oil can be lost at 45+ PSI enen through a small lopening. I'd suspect the opening in the picture with the engine operating and the oil system under pressure expands some.