Paleontology: Small dinosaurs, big diversity

A new species of small, beaked dinosaur is reported in this week’s Nature Communications. The discovery suggests that the diversity of some small-bodied dinosaur groups may be dramatically underestimated in the fossil record.

David Evans and colleagues describe from fossil records a new species of Pachycephalosaur, Acrotholus audeti. The authors reconstruct its phylogenetic tree using 16 extinct species and 50 morphological characters. The results indicate that Pachycephalosaur diversity has been significantly underestimated even for intervals with rich fossil records. Pachycephalosaur diversity also appears to be much higher than that of other groups of small-bodied dinosaurs.

Small dinosaurs are less likely to be preserved as fossils because their small bones would have been easily destroyed by carnivores, or broken down through weathering processes and the reworking of soils and sediments by animals or plants. Investigating the full range of diversity within groups of small dinosaurs is therefore difficult. The authors suggest that discovering a higher diversity of small-bodied dinosaurs would significantly alter our understanding of the diversity dynamics of dinosaurs through the Mesozoic, and their pattern of species richness leading up to the end Cretaceous extinction.