Developing a measurement protocol, part 1
By now, those of you who have been entering data from the literature — and maybe even more those who have been measuring bones themselves — will have noticed that it’s not quite as straightforward as it sounds. Some bones are crushed, distorted, broken, reconstructed, lost in soft peat for three months and recycled as firelighters. And what exactly is the “length” of a curved bone like the femur of many ornithopods? And where exactly is the “midshaft” that’s measured for the midshaft diameter? And so on.
We want to develop an explicit protocol for what bones are worth including, what measurements need taking and how they should be taken. But to do that, we’ll need your help. We want to know what issues you’ve come up against as you’ve worked on ODP data, so we can figure out standard answers. Post your questions as comments to this article: we’ll discuss them in the comments, and when we feel we have consensus, we’ll start to assemble a protocol document.
Our general feeling is that yes, there will be minor errors and distortions in the data, but there is no reason to suspect systematic bias and therefore not much to worry about (and not much we can do about it). Hopefully the database that we’re putting together will live forever and in the future people will revisit these specimens and submit “cleaned up” measurements in cases where that’s warranted. But that doesn’t mean we can’t be doing useful stuff in the meantime. It also doesn’t mean that we shouldn’t acknowledge these problems and fix them wherever possible.
So: (a) yes, crushing, distortion, reconstruction, measurement conventions, etc. are all valid concerns; (b) we will strive to overcome them to the extent possible, both immediately for the first paper and ultimately for the evolving database; but (c) these problems plague any large quantitative study of morphology — the only difference with the ODP is that those problems are out in the open; and (d) we don’t anticipate systematic bias and don’t think these problems are serious enough to prevent us from doing useful work right now.
Right then: questions, please!