Should we name fragments?

The title of this was goign to be about names, but after the last two, I thought that no-one might be reading anymore! Still, it kind of is about names, but in a rather different way than the previous posts.

It is appropriate that I am doing this piece now as a new genus has just been unveiled by my friends and colleagues Mike Taylor and Darren Naish that rather illustrates my point. Darren touches on the points I am about to make in his post and it is something he has alluded to in the past, but I wanted to tackle it myself.

The issue at stake is, in short: when should you name a new species (or genus etc.) when the available material is less than complete?

Of course the vast majority of fossils are incomplete (even taking into account the fact that with dinosaurs we are typically dealing with just bones!) – you pretty much never have all of the bones preserved, and if they are all there, some will be crushed or distorted. What I am really driving at here are the really fragmentary ones. The names given to single bones, or (as in the recent case of Xenoposeidon) parts of single bones. Is this really a legitimate practice? Is it not just wasting time and effort naming little crappy bits that are effectively meaningless? Well, hopefully I can elucidate a bit and bring out a few reasons why not only is it a good idea, it is often essential.

Naturally, as a good scientist, the first thing I will do is cover my back! Of course there is bad taxonomic practice in the literature. There are tons of unreliable names attached to incomplete fragements and even whole skeletons which really should not be named, and fixing them is a huge amount of effort and often very confusing for researchers. So, you ask, if this is already the case, why are you advocating naming bits of bone that are just that – bits?

Well the big issue is one of diagnosis. Can you take a bone (or part) however small and prove that it does not belong to anything else known at the time (as well as identify what sort of animal it is from). Often, we can. All kinds of bits of skeletons are diagnostic for various groups – dinosaurs have one kind of femur, theropods have a certain kind of astragalus (ankle bone), dromaeosaurs have a special carpal (wrist bone) so even a partial carpal can let you narrow the field down to a small family of dinosaurs, or even a genus!

Thus, with a good anatomical knowldege you can find a bone fragment, work out that it is, say a partial tibia, note that it is from an allosaur of some kind and then compare it to other allosaurs. If there are no allosaurs known from that region or that time period (allowing for quite a margin admittedly) or if it has some feature unknown in other allosaurs then it is reasonable to think it is new. But, and obviously this is the key bit, should we give it a name?

We could just called it ‘allosauroid indeterminate’, or ‘assumed allosauroid’, or even ‘possible Allosaurus’ and leave it at that. We have a record of the specimen and have a reasonable idea of what it is, so why bother to give it a formal name.

The point here is that properly named taxa are treated rather differently (and understandably more importantly) than indeterminate taxa. If I want to analyse how many allosaurs are known, or how how many predators there are in a given region I can only used named taxa. If we are not sure what they are (i.e. indeterminate) that I can’t use them in my studies. But if we are sure that they are new and independent of others then they *should* be named. It may sound like a minor point, but it is critical to how we understand the evolution, diversification, biogeography and ecology of dinosaurs to know what is a ‘real’ taxon, and for that it must be named.

If these kinds of things go unnamed we can potentially lose a huge amout of information. In trying to estimate dinosaur diversity, or analyse which groups made it onto which continents we could come to completely the wrong conclusions by eleminating taxa that are considered indeterminate, when in fact they are unique and identifiable. Thus, while it is all too easy to assume palaeontologists are time wasting with naming small fragments, there is a very real and important purpose to this process. Don’t just dismiss it at first glance because the bone in question doesn’t look like much – it probably tells the right story to the right people in the right way, and without that name, we really could not use it in the right manner.

It is a shame that taxonomy is often at the heart of such major questions in palaeontology and as a result can been seen in a negative light – it comes over as just quibbling between people over exact names and definitions. But without these names and this kind of work we could never complete the research we need to. If you take it to an extreme, how would we compare a Tyrannosaurus with a Triceratops if the names were not formally tied to a descrtiption and a skeleton for us to compare them to one another? How would we know which is which, or who was talking about which in a paper?

So do spare a though for people like Mike Taylor who go to the enormous amout of trouble to check, cross-reference, describe, diagnose, and most importantly, name these specimens. There is potentially a huge amout of information locked up in each one, and while it might just be a fragment for nopw, we might find the rest one day.

This is a revised version of a Mk.1 post, to see the original with comments etc. go here.

1 Response to “Should we name fragments?”

  1. 1 What can you do with a fragment? « Dave Hone's Archosaur Musings Trackback on 27/03/2011 at 12:14 pm
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