Microraptor in UV, wider implications

Microraptor gui holotype legs feathers under UV light. Modified from Hone et al., 2010.

So having covered the basics of the new Microraptor paper, it’s time to move beyond a single specimen of a single dromaeosaur and talk about the wider implications of the paper. For all the attention that feathers have had in the last few weeks (and there has been quite a bit, and fully deserved at that, and with more to come too) it’s worth remembering that at the core of these papers, new methods tell us new things about old (or in the case of Microraptor, not quite so old) specimens.

Researchers have been using UV light to look at fossils for decades, but a lack of powerful lights and limited interest meant that few people saw much and if they did, didn’t write about it or explain what they did in any detail. UV work has kept going and that have long been proponents out there and people making use of UV light to find new features, or just improve the contrast been bones and matrix. However, it is also probably not unfair to note that my colleague Helmut Tischlinger is largely responsible for bringing the science of UV light work on fossil vertebrates forward in enormous leaps and bounds, and that his work has been highly significant. However, Helmut also works most on pterosaurs which simply don’t get much attention (let’s face it) and also publishing primarily in the German language in small German journals was never likely to reach a huge audience. That is a problem given the importance that this method can have for interpreting fossils and finding new information on them. This lack of awareness is certainly starting to change with UV work slowly gaining attention and prominence but I hope that this paper will accelerate that process. PLoS1 is, after all, an open access journal and UV stuff is not especially hard to do. Now there is extensive documentation of the methods in a very well distributed format, and that can only be a good thing bearing in mind the results that UV can bring.

For example, while we can now say fairly confidently that the feathers of Microraptor are in a genuine position and are present, just not visible in the ‘halo’ we can also transpose this hypothesis at least to other specimens. Given the life-like position of the feathers and the way in which feathers do articulate in living birds, combined with the results of the UV work, we can be fairly confident that other specimens showing the same halo pattern do have their feathers preserved, but just hidden. Obviously we want to test this on a few more specimens with further investigations, but a whole new wave of inferences are possible about a wide range of specimens based on this work. Unless there is obvious disruption to the layout of the feathers, it’s pretty safe to assume that the feathers are present, even when preserved in a halo.

A fossil lizard with a regrown tail under UV light. Modified from Tichlinger & Wild, 2006.

More importantly, this brings forwards the fact that things can be completely hidden in natural light but wonderfully clear in UV. There are far better examples of this that Microraptor in the literature, but again, probably little read. This aspect is particularly important – most fossils go through quite a bit of preparation work before researches study them and this primarily involves stripping off the rock from around any bones or visible bits of soft tissue. The key word being ‘visible’. If things are not visible in natural light, and the perparator is not using UV, then he won’t see things that might be preserved. In other words, huge amounts of fossil information, most notably the normally rarely preserved soft tissues can be lost because the people don’t know they are there.

This is critical really. Places like the Solnhofen and Lainoning yield incredible looking fossils with both stunning and stunningly important preservation of soft tissues. And yet, that soft-tissue information that we value the most might be being destroyed in the search for the bones it surrounds. In short, we really must start using UV light extensively to check specimens from Lagerstaat deposits before and during preparation to make sure we are not stripping out otherwise invisible soft tissues. Based on Helmut’s work in the Solnhofen it has certainly happened in the past and at least one museum now regularly prepares material with UV (as happened with Juravenator for example). Long may it continue, and more importantly, the faster it spreads the more chance we have of being able to write papers like this in the future where we can get new information out of otherwise ‘exhausted’ specimens.

Hone DWE, Tischlinger H, Xu X, Zhang F (2010) The Extent of the Preserved Feathers on the Four-Winged Dinosaur Microraptor gui under Ultraviolet Light. PLoS ONE 5(2): e9223. doi:10.1371/journal.pone.0009223

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