The Cretaceous Terrestrial Revolution (abbreviated KTR) describes the intense diversification of angiosperms, insects, reptiles, birds, and mammals during the Middle to Late Cretaceous. Before the paper described the KTR, it had been widely accepted in paleontology that new families of dinosaurs evolved during Mid to Late Cretaceous, including the euhadrosaurs, neoceratopsians, ankylosaurids, pachycephalosaurs, caracharodontosaurines, troodontids, dromaeosaurs, and ornithomimosaurs. However, the authors of the paper have suggested that the apparent "new diversification" of dinosaurs during this time is due to sampling biases in the fossil record, and better preserved fossils in Cretaceous age sediments than in earlier Triassic or Jurassic sediments.