Yes, it’s self promotion time again as I have a new paper out in PloS1. The press embargo ends today, hence my posting this up now, but the paper is not officially out till Monday. As ever with PLoS, it’s free online so don’t waste my time or yours asking me for a reprint, download it from here (link should go active on Monday).
The origin of this paper lies with Helmut Tischlinger’s trip to China which involved lots of UV light work. Some of that has already turned up in print via Jeholopterus but constraints in paper length meant we did not get to include everything we would have liked to talk about and that is rectified here, in addition to the new information on the Microraptor holotype. Those keeping up on UV light work and its ability to spot various things (including fakes, on occasion) will know that bones, matrix and especially soft tissues often look very different under UV than under natural light. As a result, with the right techniques and equipment you can find some interesting details and get more information from your fossils.
First off here I will freely admit that the results here are far from Earth shattering, but they are a neat demonstration of a technique that, outside of the pterosaur community, still seems to be very little know. Hopefully this will help make more people aware of what UV can and cannot do and get people using these methods. As hopefully will become clear, this is potentially really quite important.
So, onto Microraptor, or more specifically, the holotype specimen on Microraptor gui. While there are a number of specimens of this and other species, this is probably the best, certainly the most famous and most studied, and thus arguably the most important one. While there are obviously large numbers of well preserved feathers on the slab and that they are both associated with, and structured around, the skeleton something else is also pretty clear: the feathers don’t actually reach the bones. Instead there is a ‘halo’ of space between where the bones are and the feathers start.
This is actually quite common in Lianoning specimens both in other feathered dinosaurs and also birds, and it’s also problematic. If you look at modern birds, the big flight feathers penetrate deep into the skin and basically reach the bones (hence you get quill knobs, as also now seen even in dromaeosaurs). If the feathers are not replicating this pattern (and they don’t seem to be) then the obvious question is what has happened? In some fossils, the feathers do reach the bones, both in Liaoning stuff and things like Archaeopteryx (and yes, Tianyulong too) so why not here? The obvious answer is that the feathers have moved – they are, after all, preserved next to a corpse and could easily have come free and drifted off from the bones, or perhaps they have not been preserved close in, or were destroyed during preparation or some other reason.
However, what the UV light study shows is that the feathers were, at least in part, there all along. What has happened is that the soft tissues have decayed and spread out around the specimen. You can see them incredibly clearly under UV where they shine brightly and are very pale. This is likely what is covering the feathers in most cases, but can we be sure? Close in on the legs and it certainly looks it. Several ‘arcs’ of feathers now penetrate the halo and the arc continues into the halo to the bone, though the soft tissues make it hard to see. (I should note here that good though these pictures are, this is of course much clearer when you are looking at the original slides, and better still with the original specimen itself – photos are good, reality is better). Even better are the feathers around the throat / chest where the filaments really are quite clear under UV where they are simply not visible under natural light. But what does this mean for Microraptor?
In short, it means that the feathers as we see them on the slab are very likely in their original and natural positions. They have not decayed, or moved or generally been disturbed: they are simply obscured. Secondly, this means that Microraptor’s feathers are pretty similar to those of birds and other dinosaurs in that they do, in many places, actually reach the bones of the animal. It also means that a number of measurements made of the feathers and associated calculations based on those measurements are likely in error. The feathers are longer than assumed.
All of this is pretty much as expected in a sense. We do have other specimens that suggest the pattern of feathers reaching the bones is normal. We know from modern birds that this is what we might expect. There were a variety of reasons that could plausibly lead to the feathers apparently being absent, but to be able to confirm that they are not and offer an explanation why is quite nice. What is means more generally however is perhaps more important, but you’ll have to wait for the next post for that.
Oh yes, and ReBecca over at Dinochick has an interview with me and a bit more on the methodology and history behind the paper. Edit: further coverage from friends and colleagues at Dracovenator, The Whirlpool of Life, and Dinosaur Tracking. Thanks to all.
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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