This site presents the idea that birds developed from flying pterosaurs.
This is a credible alternative to the current, mainstream idea that birds developed from land-based dinosaurs.
The fossil of a small, predatory dinosaur discovered in Germany has experts rethinking how feathers developed among the dinosaurs that likely gave rise to birds.
The authors say the new species undermines the notion that a covering of simple, hairlike feathers was characteristic of such early theropods as was previously believed.
Given its position in the dinosaur family tree, Juravenator "should bear filamentous feathers," Xing Xu said in an interview. But Chiappe says the new fossil didn't seem to bear any physical evidence of feathers, missing or not. "You could expect to see follicle [in the skin], small pits that contain feather buds. We don't see them inJuravenator," Chiappe said.
The face of a frog: Time-lapse video reveals never-before-seen bioelectric pattern
For the first time, Tufts University biologists have reported that bioelectrical signals are necessary for normal head and facial formation in an organism and have captured that process in a time-lapse video that reveals never-before-seen patterns of visible bioelectrical signals outlining where eyes, nose, mouth, and other features will appear in an embryonic tadpole.
In developmental and evolutionary biology, particular emphasis has been given to the relationship between transcription factors and the cognate cis-regulatory elements of their target genes. These constitute the gene regulatory networks that control expression and are assumed to causally determine the formation of structures and body plans. Comparative analysis has, however, established a broad sequence homology among species that nonetheless display quite different anatomies. Transgenic experiments have also confirmed that many developmentally important elements are, in fact, functionally interchangeable. Although dependent upon the appropriate degree of gene expression, the actual construction of specific structures appears not directly linked to the functions of gene products alone. Instead, the self-formation of complex patterns, due in large part to epigenetic and non-genetic determinants, remains a persisting theme in the study of ontogeny and regenerative medicine. Recent evidence indeed points to the existence of a self-organizing process, operating through a set of intrinsic rules and forces, which imposes coordination and a holistic order upon cells and tissue. This has been repeatedly demonstrated in experiments on regeneration as well as in the autonomous formation of structures in vitro. The process cannot be wholly attributed to the functional outcome of protein–protein interactions or to concentration gradients of diffusible chemicals. This phenomenon is examined here along with some of the methodological and theoretical approaches that are now used in understanding the causal basis for self-organization in development and its evolution.
