de Beer (Nov. 1, 1899 – June 21, 1972) was an English zoologist and morphologist who contributed to experimental embryology, anatomy, and evolution. He refuted the germ-layer theory and developed the concept of paedomorphism - the retention of juvenile characteristics of ancestors in mature adults).
From examination of the fossil
Archaeopteryx, De Beer proposed mosaic evolution with piecemeal evolutionary changes to explain the combination of bird and reptile features.
From Today In Science History.