Gastrulation is a process common to nearly all metazoan organisms during which an embryo with distinct tissue layers develops out of a seemingly unstructured assembly of cells referred to as ...

This model successfully predicted the complex gastrulation flows—the movement of tens of thousands of cells within the chick ...

The authors therefore propose that, compared to anamniotes, the chick (and possibly all amniotes) evolved an additional intercalation event that occurs in the ectoderm and precedes gastrulation.