The Trace Fossil Diplichnites – A New Occurrence in Eastern Ontario

 The trace fossil Diplichnites was named by Professor Dawson of McGill University in a paper presented about 140 years ago.   It is a trackway that consists of two parallel rows of blunt to elongate to ellipsoidal, closely spaced tracks.   It can be contrasted with the trace fossil Protichnites which is a trackway that consists of two parallel rows of imprints surrounding a medial impression.

Interestingly, the trace fossil Protichnites and the trace fossil Diplichnites are often found at the same occurrence.    For example, Alexander Murray of the Geological Survey of Canada reported on such an occurrence in 1852, the same year  William E. Logan and Professor Owen were presenting the initial papers on Protichnites.  

Various researchers have commented on the association of Protichnites with Diplichnites.  A few have suggested that “the Diplichnites may have been undertracks that penetrated to the underlying layer of sediment, and the fossil trackways thus produced on the top surface (preserving the impression of the dragging tail) were Protichnites” (Wikipedia).     In contrast, others suggest that the Diplichnites tracks occur on the surface.  For example, a recent paper discussing a few Diplichnites trackways in the Potsdam Group sandstones in Quebec mentions that  “Examples with pushback mounds and examples that occur on bed surfaces with adhesion structures are not likely undertracks; their lack of central drag marks suggest that some tracemakers held their tails aloft...” (Hagadorn, Lacelle and Groulx, 2012).   A third possibility is that the tracksways grade into one another.    This was noted by a researcher who reported that  “Several tracks of  Diplichnites are also present, with a medial drag mark appearing in places, grading into  Protichnites.” (Charles. T. Hoxie, 2005).

Below I’ve provided photographs of specimens of Diplichnites trackways from the same outlier of Potsdam Group sandstone between Kingston and Perth where I found the specimens of Protichnites mentioned in my last blog posting.

Photos SAM_0491  and SAM_0492 were taken of the same slab.  They show a Diplichnites trackway (two parallel rows of  tracks) crossing ripple marks.   This is likely the sole of an overturned slab, as the footprints are in positive relief.

Photo SAM_0435.JPG is a different slab.    It clearly shows two parallel rows of tracks.

Photo SAM_0438.JPG  is a  specimen  that  was collected close to the specimen shown in Photo SAM_0435.JPG.  There is one good  line of circles (arguably paired  with another line of circles),  plus     crossing lines of  circles,  plus numerous  other circles.

  

Below are photos   SAM_0495 and SAM_0497 of two slabs that might bear the trackway Diplichnites.

       

Christopher P. Brett
Perth, Ontario