New evidence on the colour and nature of the isolated Archaeopteryx feather

Abstract

Archaeopteryx has been regarded as an icon of evolution ever since its discovery from the Late Jurassic limestone deposits of solnhofen, Germany in 1861. Here we report the first evidence of colour from Archaeopteryx based on fossilized colour-imparting melanosomes discovered in this isolated feather specimen. using a phylogenetically diverse database of extant bird feathers, statistical analysis of melanosome morphology predicts that the original colour of this Archaeopteryx feather was black, with 95% probability. Furthermore, reexamination of the feather's morphology leads us to interpret it as an upper major primary covert, contrary to previous interpretations. Additional findings reveal that the specimen is preserved as an organosulphur residue, and that barbule microstructure identical to that of modern bird feathers had evolved as early as the Jurassic. As in extant birds, the extensive melanization would have provided structural advantages to the Archaeopteryx wing feather during this early evolutionary stage of dinosaur flight.

Experimental maturation of feathers: implications for reconstructions of fossil feather colour

“…Other pigments and colourproducing nanostructures generate colour in the feathers of many extant birds and can modify colour generated by melanosomes [9], but fossil evidence of these mechanisms is elusive; the relative preservation potential of the various colour-producing mechanisms in feathers is unknown. Several studies have inferred the original coloration of fossil feathers by comparing the preserved geometry and/or spatial arrangement of melanosomes to those in extant analogues [4][5][6]8,10,11]. These reconstructions assume that data from fossil and modern feathers can be compared directly, but the fidelity with which melanosomes are preserved is unknown.…”

Bacteria or melanosomes? A geochemical analysis of micro-bodies on a tadpole from the Oligocene Enspel Formation of Germany

“…the chemical pigment melanin is synthesized. This reinterpretation is based on a growing number of studies citing both morphological (Vinther et al 2008;Clarke et al 2010;Zhang et al 2010;Li et al 2010Li et al , 2012Carney et al 2012) and geochemical evidence Wogelius et al 2011;Glass et al 2012;Lindgren et al 2012Lindgren et al , 2014, though the debate is by no means settled (Moyer et al 2014). Extant melanosomes are known to exist in both spherical and elongate forms depending on the type of melanin they contain (Liu et al 2005), though this is not always the case (Liu et al 2005).…”

Interpreting melanin-based coloration through deep time: a critical review

“…[6,50,51]), yet the search for ancient melanic pigments only began in earnest in the late 2000s following the proposal that feather traces might infer evidence of original hues and shades [7,52]. Since then, a number of investigations have used chemical markers and presumed fossil melanosomes to explore aspects of the biology and ecology of extinct animals, including colour [8,9,[53][54][55][56][57], behaviour [8,56] and physiology [10]. However, studies reporting remnant melanosomes have been met with controversy, and an alternative hypothesis has been put forth favouring a more conservative interpretation of the fossil microbodies as microbes colonizing the degrading tissues prior to burial [12,58].…”

“…Melanin insolubility, imparted by abundant intramolecular cross-links, has been argued to contribute to the preservation of integumentary structures in fossils, and especially feathers (e.g. [54]). However, the assumption that melanin unanimously confers degradation resistance to the enclosing organelles, or the surrounding keratinous tissues,…”

“…This is critical for evaluating the many published accounts on presumed melanosomes in fossils, because the majority of those specimens where expressed colour, physiology, behaviour or evolutionary significance have been proposed do not illustrate three-dimensional bodies, but rather derive data from ovoid to elongate imprints within an uncharacterized matrix (e.g. [8][9][10]54]). This observation implies that the microbodies decay more rapidly than does the surrounding matrix, thus challenging the idea that melanin confers decay resistance to the bodies.…”