What is a “Well Preserved” footprint?

A somewhat belated blog post about my recent paper with Stephen Gatesy, published in JVP (If you don’t have access, just drop me an email).

It’s one of the papers I’m most proud to have worked on, because I think it’s a really interesting discussion about what we mean when we say a track is “well preserved” or “poorly preserved.”

Essentially, the two terms have traditionally been used almost synonymously with “foot-like” and “less foot-like.”  But as the title of our paper, “Neither bones nor feet” suggests, that may be inadvertently misleading.

In our paper we make the case that “preserved” terms should only indicate how much a track has been altered after it has been formed.  What does that mean?  Well, our figure 2 summarises this nicely:

Gatesy and Falkingham 2017 fig 2.JPG

All of the above tracks are “perfectly preserved”, in as much as we recorded them with photogrammetry immediately after they were made.  But if found in the fossil record, it wouldn’t be uncommon to see B, F-H referred to as “poorly preserved”, because they don’t look like feet; it would be difficult or even impossible to measure things like toe length, or even toe number from some of those tracks.

If you’re interested in what animal made a track, you probably are concerned with how much the track looks like the anatomy of the trackmaker’s foot. But if you’re interested in function, and how the foot is moving and the track is made (as we generally are), you will be equally interested in all these tracks (in fact, probably least interested in the “well preserved” C).

We make the case (reasonably convincingly I think) that we should use the term ‘preserved’ in the same way we do with bones: That is, pathologies and the like have no bearing on how ‘well preserved’ a bone is described as, only how much the bone altered after the animal’s death. To that end, we summarise our thoughts with this:

Gatesy and Falkingham 2017 fig 5.JPG

Whereby we essentially consider end of track formation (which we define as all energy imparted by the foot ceasing to displace sediment; allowing for slumping and the like to be part of track formation) analogous to the death on an animal.

As I say, I’m really pleased with how this paper turned out, so go read it and see what you think.

Gatesy, S.M. & Falkingham, P.L. (2017): Neither bones nor feet: track morphological variation and ‘preservation quality’, Journal of Vertebrate Paleontology, DOI: 10.1080/02724634.2017.1314298

 

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