The early evolution of feathers: fossil evidence from Cretaceous amber of France

Abstract

The developmental stages of feathers are of major importance in the evolution of body covering and the origin of avian flight. Until now, there were significant gaps in knowledge of early morphologies in theoretical stages of feathers as well as in palaeontological material. Here we report fossil evidence of an intermediate and critical stage in the incremental evolution of feathers which has been predicted by developmental theories but hitherto undocumented by evidence from both the recent and the fossil records. Seven feathers have been found in an Early Cretaceous (Late Albian, ca 100 Myr) amber of western France, which display a flattened shaft composed by the still distinct and incompletely fused bases of the barbs forming two irregular vanes. Considering their remarkably primitive features, and since recent discoveries have yielded feathers of modern type in some derived theropod dinosaurs, the Albian feathers from France might have been derived either from an early bird or from a non-avian dinosaur.

New evidence of feathers in the Crato Formation supporting a reappraisal on the presence of Aves

“…5). It is very similar in morphology to feathers preserved in amber from the Early Cretaceous in France (Perrichot et al 2008). This feather is morphologically similar to the down or ornamental ones, and not to the contour, remiges or rectrices.…”

“…In that morphotype, paired barbules within the peripheral barbule plates of the barb ridges, created the branched barbs with rami and barbules. This is considered the most critical stage of a feathers evolution in birds or non-avian dinosaurs since it is present in both (Xu 2006, Perrichot et al 2008. The GP/2T-136 specimen does not fit in any of the known morphotypes.…”

“…Developmental theories propose that feathers evolved through a series of evolutionary novelties in the developmental mechanism of the follicle and feather germ (Dyck 1985, Prum 1999, Chuong et al 2000, Prum and Williamson 2001, Prum and Brush 2002, Perrichot et al 2008, Xu et al 2010). In this model, feathers were divided originally into five morphotypes (Prum 1999), refined in subsequent works to nine (Perrichot et al 2008, Xu et al 2010.…”

“…In this model, feathers were divided originally into five morphotypes (Prum 1999), refined in subsequent works to nine (Perrichot et al 2008, Xu et al 2010. Feathers from the Crato Formation belong to morphotypes II, III, and probably V. The morphotype II resembles to a tuft of unbranched barbs with a basal calamus (Prum 1999), very similar to MPSC-PN 2221.…”

Non-invasive imaging methods applied to neo- and paleo-ontological cephalopod research

“…The scan time for one small object (5 mm) takes about 5-20 min, depending on the set-up, but larger objects can also be scanned with high accuracy and resolution. High resolution means in this case that the resolution can be less than 0.7 µm (Baruchel et al, 2006;Friis et al, 2007;Perrichot et al, 2008;Pouech et al, 2010;Sanchez et al, 2012;Tafforeau and Smith, 2013;Moreau et al, 2014;Fig. 10).…”