The reconstruction of ancient life has long required a certain degree of imagination. This is fundamental when considering the colouration of long-extinct organisms. However, new methods of investigation are being incorporated into palaeontology that may cast new light (and colour) on fossils. Research presented at the recent Society of Vertebrate Palaeontology meeting demonstrates the significance of utilising new imaging technologies in reconstructing the colour of Archaeopteryx, one of the most famous and important fossil species.
Ryan Carney from Brown University integrated scanning electron microscopy in a 2012 study in order to identify melanosomes (melanin-containing pigment structures) in modern feathers to reconstruct the feather colour of the iconic Archaeopteryx, the so-called “missing link” – or more appropriately, the evolutionary intermediate – between non-avian dinosaurs and birds. Archaeopteryx has also been referred to as the “Mona Lisa of palaeontology,” a fossil taxon with great scientific, historical, and cultural importance.
However, after Carney’s original publication, there has been some recent controversy regarding two competing papers that provide alternative interpretations. The first was that the Archaeopteryx feather was both black and white, based on the distribution of organic sulfur imaged via synchrotron. The second was that the fossilised microbodies in the feather represent bacteria rather than melanosomes, given their similarities in size and shape.
The results of Carney’s new research address these alternative interpretations and gives new insight into the Archaeopteryx feather. “The inner vane of the Archaeopteryx feather, which they claimed was white, we instead found to be packed with black melansomes,” said Carney. “This is critical because white feather colour is only produced in the absence of melanosomes.”
Additionally, Carney and his Swedish colleagues have investigated the preservation of melanosomes in numerous other fossils, utilising additional new analytical methods such as Time-of-Fight Secondary Ion Mass Spectrometry (ToF-SIMS). Carney added, “We are not contending that every fossilised microbody is a melanosome. However, this new chemical method has allowed us to detect actual melanin molecules, which are associated with the melanosome-like microbodies in fossilised feathers and skin, from both terrestrial and marine environments. This integrated structural and direct chemical evidence provides the definitive proof that melanosomes can indeed be preserved in the fossil record.”
Together, this novel research constructs the final picture of the famous wing feather as matte black with a darker tip, colouration that have allowed structural advantages to the plumage during this early evolutionary stage of dinosaur flight.
The application of such high-sensitivity analytical techniques is leading in a new age of palaeontological investigations. What was once artistic license, such as the appearance of ancient organisms, is now revealing itself in living colour. As analytical methods in palaeontology keeps a pulse on technological advancements, we will continue to obtain an understanding of how fossil animals once lived and looked.
Contributing Source: Society of Vertebrate Palaeontology
Header Image Source: Wikimedia