Although angiosperm diversity drastically grew over the Cretaceous, this did not necessarily translate to ecological dominance, which they only achieved in the Early Cenozoic. Angiosperms responded to increasing coevolution with frugivores by enlarging the sizes of their fruits, which peaked during the Early Eocene. Before Lloyd
et al.'s 2008 paper described the KTR, it had been widely accepted in
paleontology that new
families of
dinosaurs evolved during the Middle to Late Cretaceous, including the
euhadrosaurs,
neoceratopsians,
ankylosaurids,
pachycephalosaurs,
carcharodontosaurines,
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. However, later studies still suggest the possibility that the KTR caused a rise in dinosaur diversity. Dinosaurs contributed little to angiosperm diversification, which was instead mainly driven by coevolution with other animals, such as insects and herbivorous mammals. It has been suggested that some pterosaurs may have been seed dispersers symbiotically linked to angiosperms. A comprehensive molecular study of evolution of mammals at the taxonomic level of family also showed important diversification during the KTR. Mammals diversified extensively during the KTR, but also decreased in disparity. Insect diversity overall appears to have been minimally affected by the KTR, as molecular evidence shows that the increase in diversity of pollinating insects was asynchronous with the KTR. Spikes in both insect origination and extinction rates during the KTR were correlated with high global temperatures. However, Early Cretaceous angiosperms were short in stature and would have been heavily reliant on insect pollination, There is also evidence suggesting that terrestrial arthropods may have preferentially preyed on angiosperms. Genetic evidence indicates a major radiation of
phasmatodeans occurred during the KTR, likely in response to a coeval radiation of
enantiornitheans and other visual predators.
Ants likewise underwent massive increase in diversity as part of the KTR. Similarly, bee pollinator diversification strongly correlates with angiosperm flower appearance and specialization during the same era.
Flies, already successful pollinators before the rise of angiosperms, quickly adapted to the new hosts.
Beetles became pollinators of angiosperms by the earliest part of the Late Cretaceous. Lepidopterans radiated during the KTR, though the angiosperm radiation is insufficient in and of itself to completely account for their diversification. Among one lineage of
sawflies, there was a change in preferred host plants amidst the biotic reorganisation of the KTR. Not all insects were advantaged by this diversification and rearrangement of ecosystems; long-proboscid insects that were mainstays of gymnosperm-dominated ecosystems earlier in the Mesozoic underwent a major decline. The so-called "golden age" of neuropterans during the Middle Mesozoic, when gymnosperms dominated the flora, ended with the KTR and its reshaping of the terrestrial environment.
Mesoraphidiids went extinct during the KTR, likely due to the habitat preference of their larvae of gymnosperms, although
alloraphidiine mesoraphidiids increased in disparity in the Late Cretaceous in response to the KTR. The KTR may have supercharged the contemporary
Mesozoic Marine Revolution (MMR) by enhancing weathering and erosion, accelerating the flow of limiting nutrients into the world's oceans. For nearly the entirety of
Earth's history, including most of the
Phanerozoic eon, marine
species diversity exceeded terrestrial species diversity, a pattern which was reversed during the Middle Cretaceous as a result of the KTR in what has been termed a biological "great divergence", named after the historical
Great Divergence. ==See also==