Cambrian mystery trace fossil

I have been puzzled by this Early Cambrian trace fossil ever since I collected it about 35 years ago while on a field trip with my paleontology class. The trace consists of two parallel grooves that show up on the bottom of a bed of slightly metamorphosed sandy siltstone. What you see is the sediment that infilled the grooves (the sediment constitutes a cast). The trace is from the Inyo Mountains, California. I wonder what kind of animal could have made this trace. Did a single animal make it while crawling over the surface of the muddy sediment? Or, did two animals crawling alongside each other make the grooves?

I have tentatively identified this trace fossil (i.e., technically speaking, an ichnofossil) as Scolicia sp.

If anyone has a better identification, please let me know via the comments option on this blog site.