The wing of the bird-like feathered Anchiornis dinosaur under laser-stimulated fluorescence. The folds of skin in front of the elbow and behind the wrist (called patagia) were covered in feathers, just like in modern living birds. Photo by Wang XL, Pittman M et al., Nature Communications, 2017.
Several major advances in dinosaur research have been announced over the past several weeks. Two of the announcements are discussed in this blog, via two posts. This is the first post:
In February 2017, news broke regarding the application of special lasers to scan actual fossils still embedded in the surrounding matrix (Basal paravian functional anatomy illuminated by high-detail body outline; Nature Communications, February 28, 2017; Nature.com March 1, 2017).
There is nothing new about scanning fossil bones with lasers. In the 90's, research involving the "digitization" of fossils was in its infancy, with the first serious "breakthrough" attempts exploring the possible use of lasers to scan bones to obtain data sets that, in turn, were used to create 3D models. In fact, I was involved in some of that work, with a team applying high-end laser scanning tests to the selected bones of the famous "Sue" Tyrannosaurus rex, in the mid 1990s. This was a major breakthrough, being among the first applications of 3D laser scanning technology to hard-core dinosaur science. Until then, 3D imaging was limited to Hollywood special effects labs and industrial design. The scans of "Sue" eventually led to the first 3D laser scan modeling of an entire dinosaur for the Smithsonian Institution.
These "early" 3D scans were done using lasers mounted on various forms of moving trackways, that circumnavigated the bone being scanned while shining a laser beam on the fossil along the way, until the entire specimen was digitally mapped. This equipment was rare, expensive to obtain and complicated to use. At the time, no dinosaur department had such equipment, and they lacked the expertise to use the tools. Any researcher wishing to laser scan a specimen had to out-source for the hardware, software and expertise.
Over the next 10 years however, this expensive process of outsourcing for "outside" laser scanners became replaced by researchers opting to use already existing laser scanning tools, in the form of CT scanners, that were already being used in nearby university medical departments or hospitals. This became a convenient, cost effective and efficient method of obtaining high-quality 3D scans by dino researchers, without the hassle and overhead. Paleontologists no longer had to concern themselves with the equipment - they merely had to book time on the nearest hospital scanner, and bring a fossil along. And, being a medical grade diagnostic tool, the hospital CT scanner provided better results than the earlier, outsourced type of laser scanner - a substantial win-win for dinosaur researchers.
Today, this remains the common process for obtaining 3D laser scans of fossils, without much deviation. And it works exceptionally well for scanning and digitizing the surface of a fossil, to capture and preserve in digital format the external form of a fossil.
But a new breakthrough has occurred with a recent laser scanning project. In February, a team headed by Xiaoli Wang and Michael Pittman announced stunning results when applying lasers of a particular frequency to fossils - with a twist: the fossils being scanned were still embedded in the surrounding rock matrix they were discovered in. The fossils were of a small, feathered dinosaur discovered in China named Anchiornis huxleyi. Almost by accident, by scanning fossils not yet pried out of the matrix, the lasers revealed subtle details never seen before. This aspect was partnered with the fact that a new breed of laser was being used, based on different wavelengths than was used by previous lasers and involving a unique new process of scanning, enabling soft-tissued details to be seen - for the first time.
The new scanning process incorporated in this work is called "laser-stimulated fluorescence" (LSF). It involves sweeping non-destructive laser light across a specimen while taking long-exposure photographs with a digital single lens reflex (DSLR) camera. “The laser ‘excites’ the few skin atoms left in the matrix, making them glow, to reveal what the shape of the dinosaur actually looked like,” according to Michael Pittman, a University of Hong Kong paleontologist and one of the study’s lead authors, in an interview with PBS NewsHour writer Kristin Hugo.
Using the new laser wavelengths on fossils still embedded in the rock matrix, previously invisible outlines of skin and feathers become dramatically visible. For the first time, we can vividly see the actual contours of soft skin boundaries and detailed outlines of feathers of an entire forelimb, and their exact relationship to the underlying bones. Even the "toeprints" of the feet are presented in sharp detail.
In fact, the results immediately presented a feature not known before on a dinosaur: the arm scan of Anchiornis by this team shows that at least this species of small feathered dinosaur had a triangular "patagial membrane" (wing membrane) along the anterior aspect of the elbow. The patagium is a type of skin "webbing" along the forward part of the arm, between the humerus (upper arm) and radius/ulna (lower arm) - something only seen on modern flying birds. From now on, any accurate life illustration of this dinosaur must show this feature, along with the feathers and other details, as revealed through these new scans...
The results are like looking at a shadow silhouette of the animal when alive. We now have actual evidence for how dinosaurs actually looked in life - how the integument draped their bones. This will go a long way in enabling more accurate illustrations of dinosaurs - we still don't know much about how they were colored (although we are getting more clues about that, as well*), but as more and more of these kinds of scans are done, scientists and artists will increasingly have actual "facts" on which to base their restorations on.
Wang and Pittman et al, are proceeding to scan more fossils using this novel new approach, and will surely encounter more exciting surprises along the way.
*In fact, previous research has led to some conclusions on the coloration of this species: Anchiornis apparently was adorned with black and white patterns and a red tuft on its head.
