Background The origin of birds is one of the most enduring and dramatic evolutionary
debates. The hypothesis that the primarily small-sized birds are nested within a theropod …

All ectodermal organs, eg hair, teeth, and many exocrine glands, originate from two adjacent
tissue layers: the epithelium and the mesenchyme. Similar sequential and reciprocal …

The first comprehensive review of all aspects of the biology of moult, drawing information
from across the literature and in all birds, from penguins to passerines. Feathers are …

Abundant fossils of the terrestrial Jehol Biota, including plants, insects, dinosaurs, birds,
mammals and freshwater invertebrates, were discovered from the Yixian Formation and the …

Variable feather overlap enables birds to morph their wings, unlike aircraft. They accomplish
this feat by means of elastic compliance of connective tissue, which passively redistributes …

The feather is a complex epidermal organ with hierarchical branches and represents a multi-
layered topological transformation of keratinocyte sheets. Feathers are made in feather …

Although endochondral ossification of the limb and axial skeleton is relatively well-
understood, the development of dermal (intramembranous) bone featured by many …

Integuments form the boundary between an organism and the environment. The evolution of
novel developmental mechanisms in integuments and appendages allows animals to live in …

▪ Abstract Recent fossil discoveries from Early Cretaceous rocks of Liaoning Province,
China, have provided a wealth of spectacular specimens. Included in these are the remains …

The feather is a complex ectodermal organ with hierarchical branching patterns. It provides
functions in endothermy, communication, and flight. Studies of feather growth, cycling, and …