Feather evolution from knotted barbules to hooked and unhooked barbules and its finite element analysis

Experiments involving scanning electron microscopy of the microstructure of barbules and optical microscopy of knotted barbules were conducted: the behaviour of knotted barbules, and their evolution to form a branch of hooked barbules and unhooked barbules were analysed. A growth model for a feather plume was proposed. MATLAB™ 2-d contour microstructures of sectioned knotted feathers and three-dimensional structural models of barbules were established, moreover, these were analysed using the finite element method. The response under load of different parts of the barbules was obtained. The results showed that there were stress concentrations in feather barbules. The study laid a foundation for finding the internal and external causes of the evolutionary transition of knotted barbules.

A new Jurassic theropod from China documents a transitional step in the macrostructure of feathers

Genuine fossils with exquisitely preserved plumage from the Late Jurassic and Early Cretaceous of northeastern China have recently revealed that bird-like theropod dinosaurs had long pennaceous feathers along their hindlimbs and may have used their four wings to glide or fly. Thus, it has been postulated that early bird flight might initially have involved four wings (Xu et al. Nature 421:335-340, 2003; Hu et al. Nature 461:640-643, 2009; Han et al. Nat Commun 5:4382, 2014). Here, we describe Serikornis sungei gen. et sp. nov., a new feathered theropod from the Tiaojishan Fm (Late Jurassic) of Liaoning Province, China. Its skeletal morphology suggests a ground-dwelling ecology with no flying adaptations. Our phylogenetic analysis places Serikornis, together with other Late Jurassic paravians from China, as a basal paravians, outside the Eumaniraptora clade. The tail of Serikornis is covered proximally by filaments and distally by slender rectrices. Thin symmetrical remiges lacking barbules are attached along its forelimbs and elongate hindlimb feathers extend up to its toes, suggesting that hindlimb remiges evolved in ground-dwelling maniraptorans before being co-opted to an arboreal lifestyle or flight.