There are great papers that get all the attention that they deserve, great papers that don’t get the attention they deserve, bad papers that get attention they don’t deserve and one that get just the right amount. This is one of the latter. Not, I would hasten to add, that it is not a good paper but simply that I would be surprised if many people outside of the dinosaur ichnology crowd would be particularly interested and perhaps not even them.
Yes I have a new paper out as ably led by my good friend Corwin Sullivan of Epidexipteryx fame and since I have a blog and no media outlet is ever going to pick up this one I thought I’d do the job myself. In it we describe some new fossil footprints from the Jurassic of China and try to resolve some of the ongoing issues over ichnotaxonomy (the names given to footprints) that have plagued some of the Chinese trackways and footprints for a number of years.
Corwin will perhaps be less than enthused by the title of this post, but well it’s hard for me to even get too excited about this paper, but it really actually *is* important if unexciting. One of the central things about academia and especially biology-based subjects is getting the nuts and bolts papers done so that everyone is reading from the same page so to speak. They are not exciting or interesting to write (in my opinion) and the press are never going to be impressed, but they are absolutely essential to research. You need to make sure these things are correct and sorting them out can be difficult and time consuming, but in the long run it makes life much easier for everyone. If you taxonomy is confused everything else becomes ten times harder as no-one is sure if everyone is talking about the same thing or not. If we can’t tie down names properly then everything rapidly gets confused and needs to be sorted out.
Corwin deserves all the plaudits for this as he sat and fought with the intricacies of ichnotaxonomy (and I apologise to any ichnotaxonomists who might be reading this when I say that this is a Sysyphean task) of Chinese theropod tracks. It a very complex issue as obviously you typically have little idea what exactly made the tracks that you have found and thus ichnotaxonomy is based on what the tracks themselves look like, and not the animals that made them. So of course this means that very different animals can potentially make very similar looking tracks. Then you have the problem of track variability, individual animals or species can leave very different tracks depending on what surface they were walking on, what they were doing and how those tracks were preserved. One of the key aspects of dinosaurian ichnotaxonomy is the size of the print, and the angles between the toes. However a running animal on a hard substrate will leave widely spaced tracks, that are quite small and with narrowly diverging toes, but one walking on thick mud is likely to leave short strides, with bigger individual prints (the foot will smush the mud out) and with the toes widely spaced. Suddenly this gets tricky.
Add to all of this the long history of ichnotaxonomy, the fact that there are quite a few papers in Chinese and Japanese on the subject, and a couple of recent revisions of the likely ichnogenus for our tracks (Grallator, Anchisauripus and Eubrontes for those in the know) and you can see why I am impressed. There was a lot of work involved (both mathematical and descriptive) and I am proud (or should that be ‘ashamed’?) to say that Corwin did it all on his own and I just hid in the corner of the office and criticised occasionally from a safe position of ignorance. I find it helps people to keep them grounded in reality and not get carried away with their own genius and the praise heaped upon them. Ultimately the tracks were assigned to Anchisauripus, but the fit was not perfect and there was a reasonable case for erecting a new species within to account for our tracks, but in the end we left it as A. ispp. (This means we have left it within the ichnogenus, but have not assigned it to a specific ichnospecies as we are not sure exactly where it goes or if a new species needs to be named, a pretty common practice in palaeo where you don’t always have the best material to work with).
Anyway, so back to the actual paper at hand. What we had was a small section of trackway that had been spotted by American geologist Tim Cope and then collected from Nanshuangmiao in Hebei Province by our IVPP colleague Liu Jun (a specialist in basal reptiles) in addition to a cast being taken of some others that could not be removed. This was pretty tricky as the tracks stuck out from the underside of an overhang of rock so ever getting to them was difficult, let alone removing or casting sections.
Describing them was relatively easy: they are relatively small (though there is quite a range of sizes present), have three long thin-ish toes with the middle digit being the longest, and leave clear claw marks, making them the product of a small theropod. You can get a rough estimate of the height of the animal and its length from the size of print which tells us they were probably about 2-3 m in length. Individual tracks cannot easily be assigned to left and right tracks made by a single animal because of the variation in size, some overprinting (one track on top of another), the fact that they are all moving sub-parallel to each other and the lack of a diagnostic identification for any one track – in short despite having quite a few tracks obviously representing quite a few animals, picking out a set as being a trackway made by one individual was impossible. The beds were originally part of a fluvial system, and the track are preserved in mudstone implying the animals were walking close to a river or as part of a floodplain (the prints are pretty deep for a small, light animal so the surface was probably pretty soft and wet at the time).
Based on all of this we can surmise that we had a small group of small theropods moving along a floodplain together. All the tracks are going in the same direction, were roughly the same size and had similar morphologies so there is no reason to think they were not acting as a monospecific group. We can also say that they were travelling together and not just along a game trail since there are very few overprints which one would expect if it was a series of animals walking along a single path, and the fact that the prints do not just lie along a single line, but are spread out over an (admittedly small) area.
So there you have it all. The paper is actually quite big with lots of techie stuff on ichnotaxonomy assignation and resolution and is not for the fainthearted, and I wanted to keep this post relatively short (so much for that plan). Still I think it’s important to show hoe these kinds of papers get done and *why* they get done. As I have said before these papers are massively underappreciated by research councils and funding bodies and even hiring committees, and yet are essential to how science works. We must establish the basics of what things are, and how they vary and to what extent and when and where, without that you are simply building on shaky foundations that will only need to be fixed later and the longer they are left the harder it is to sort them out as you have to dig that that much more research to get to the initial problem, and then make sure everything refereeing to it is still accurate.
Finally I think it goes to show just how much you can infer (if carefully and with plenty of caveats) about behaviour with the right tools. All we have is a few isolated prints, but the manner in which they were laid down allows us to gather some useful evidence for sociality in theropods, something that is actually profoundly lacking from the body fossil record. The next task is of course to go back with a proper team and try and strip away the original overhangs and see if we can extract the inaccessible prints and the others that doubtless remain buried around them. I’ll let you know, but it might be quite a wait.
Sullivan, C., Hone, D.W.E., Cope, T., Liu, Y., & Liu, J. In press. New occurance of small theropod trackss in the Houcheng (Tuchengzi) formation from Hebei province. Vertebrata Palasiatica.