Early fossils demonstrate dinosaurs' slow rise

by Mary Caperton Morton
Thursday, February 9, 2017

Dinosaurs were so dominant through much of the Mesozoic that it’s easy to forget that wasn’t always the case. The discovery of a specimen of an early small dinosaur alongside a lagerpetid — a precursor to the dinosaurs — is giving scientists a glimpse into the slow-paced early stages of dinosaur evolution.

Found together in the same 230-million-year-old deposit in Brazil, a saurischian dinosaur of the genus Buriolestes and a new species of lagerpetid called an Ixalerpeton represent some of the earliest-known fossils from the Early Triassic, which began about 250 million years ago. The find, reported in Current Biology, marks the first time that a dinosaur has been found in such close proximity to a dinosaur precursor, indicating the species coexisted.

“We now know for sure that dinosaurs and dinosaur precursors lived alongside one another and that the rise of dinosaurs was more gradual, not a fast overtaking of other animals of the time,” said lead author Max Langer of Brazil’s University of São Paulo, in a statement.

The new discoveries fill some gaps in the dinosaur family tree. The new lagerpetid specimen also provides the first detailed look at the skull, scapula and forelimb of the creature, which is thought to have been a hunter of small mammals. The Buriolestes specimen is one of the oldest-known examples of a Sauropodomorpha, the group of long-necked dinosaurs that includes sauropods and their ancestors.

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