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A study by paleontologists from the UK suggests that gaps in the fossil record do not indicate an absence of dinosaurs, but rather indicate a lack of information caused by geographical and research barriers.
Scientists have found that the oldest dinosaur fossils, dating back more than 230 million years, are unevenly distributed geographically. Of particular note is the vast geographical gap around the equator, where the lack of finds may be due to difficult preservation conditions or insufficient study of the region. As Joel Heath notes,
By analyzing the distribution of fossils, the researchers hypothesized that the first dinosaurs may have originated in the southern latitudes of Gondwana, where the climate was much warmer and drier. This model contradicts previous assumptions that early dinosaurs lived in relatively mild climates.
The study also points to a possible link between early dinosaurs and silesaurids — reptiles that could have been an intermediate link in the evolution of these animals. An important discovery is that among the three main groups of dinosaurs, it was the sauropods, including Brontosaurus and Diplodocus, that retained an advantage over warm climates and low latitudes. As Philip Mannion notes,
