Laser Fluorescence Illuminates the Soft Tissue and Life Habits of the Early Cretaceous Bird Confuciusornis

Abstract

In this paper we report the discovery of non-plumage soft tissues in Confuciusornis, a basal beaked bird from the Early Cretaceous Jehol Biota in northeastern China. Various soft tissues are visualized and interpreted through the use of laser-stimulated fluorescence, providing much novel anatomical information about this early bird, specifically reticulate scales covering the feet, and the well-developed and robust pro- and postpatagium. We also include a direct comparison between the forelimb soft tissues of Confuciusornis and modern avian patagia. Furthermore, apparently large, fleshy phalangeal pads are preserved on the feet. The reticulate scales, robust phalangeal pads as well as the highly recurved pedal claws strongly support Confuciusornis as an arboreal bird. Reticulate scales are more rounded than scutate scales and do not overlap, thus allowing for more flexibility in the toe. The extent of the pro- and postpatagium and the robust primary feather rachises are evidence that Confuciusornis was capable of powered flight, contrary to previous reports suggesting otherwise. A unique avian wing shape is also reconstructed based on plumage preserved. These soft tissues combined indicate an arboreal bird with the capacity for short-term (non-migratory) flight, and suggest that, although primitive, Confuciusornis already possessed many relatively advanced avian anatomical characteristics.

Inferring lifestyle for Aves and Theropoda: A model based on curvatures of extant avian ungual bones

“…Ideally, one would compare extant and fossil claw sheaths, as the sheath interacts directly with the environment and is likely more biomechanically relevant. Theropod claw sheaths are rare but not unknown from the fossil record [19][20][21][22][23][24][25][26], and for these exceptional specimens analyses of the sheath are very useful. However, for most fossil specimens, the claw sheath is either broken or entirely absent leaving only the ungual bone, and fossilised toe pads or skin are even rarer [27][28][29][30][31][32][33][34][35][36][37][38].…”

Inferring lifestyle for Aves and Theropoda: a model based on curvatures of extant avian ungual bones

“…Theropod claw sheaths are rare but not unknown from the fossil record [24][25][26][27][28][29][30][31][32][33] . However, for most fossil specimens, the claw sheath is either broken or entirely absent leaving only the ungual bone, and fossilised toe pads or skin are even rarer [34][35][36][37][38][39][40][41][42][43] .…”

Laser-stimulated fluorescence reveals unseen details in fossils from the Solnhofen Limestone (Upper Jurassic, Bavaria, Germany)

“…With reductions to the cost of laser systems, the method could be replicated using a 532nm laser, an LCD power supply and a Zecti 31.5in"/80cm camera slider. This study using an 85mW laser shows the technique can be used with less powerful laser equipment than the 300-500mW laser used by Falk et al (2016) and Wang et al (2017). With two wavelengths in tandem, different structures uoresce, allowing for a more complete picture (Wang et al 2017), providing an option for further research.…”