Dinosaur tracks are fascinating fossils, and I’ll never forget traveling to a few local museums as a child to look at the reddish slabs from the Newark Supergroup containing the tracks of small theropod dinosaurs. To be honest, however, I didn’t really keep up with the study of tracks (I was always more attracted to the bones of the animals), but luckily some people have, and there’s a new paper out by Jesper Milan and David Loope entitled “Preservation and Erosion of Theropod Tracks in Eolian Deposits: Examples from the Middle Jurassic Entrada Sandstone, Utah, U.S.A.” (the link leads right to the paper, so don’t miss out!). This paper is particularly interesting because it acts like a mini-field guide to recognizing theropod trackways, driving home the point that not all tracks are perfect impressions in the sandstone; often they merely appear to be blobs made up of concentric rings going in a particular direction. Milan and Loope put it this way;
The direct impression of the trackmaker’s foot in the tracking surface is the true track (Lockley 1991). When an animal walks, not only is the tracking surface deformed, but also the layers subjacent to the tracking surface are deformed. Experimental work with track formation shows that the weight of the trackmaker is transferred radially outward in the sediment around and below the foot (Allen 1989, 1997), forming a stacked succession of undertracks (sensu Lockley 1991). Normally, it is possible to distinguish undertracks from true tracks in that they are less detailed than true tracks and never preserve any fine anatomical details like skin impressions.
This may seem like fairly obvious research, but oftentimes the most obvious research is that which goes undone; I really recommend that anyone with an interest in dinosaurs check this paper out as it is easy to understand and explains some ichnofossils that may easily be overlooked.