Dinosaurs like T. rex, previously thought to be smart, were not as intelligent as monkeys, a study revealed on Monday.

A study, published last year, claimed that dinosaurs like T. rex had an exceptionally high number of neurons, which could directly inform on intelligence, metabolism, and life history. It also said that T. rex was rather monkey-like in some of its habits.

In the new study, researchers from the UK, Germany, and Canada took a closer look at techniques used to predict both brain size and neuron numbers in dinosaur brains.

The findings, published in The Anatomical Record, showed that the dinosaur’s brain size as well as neuron counts had been overestimated — especially that of the forebrain.

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Instead of neuron count estimates, the team stressed the need to look at multiple lines of evidence, including skeletal anatomy, bone histology, the behavior of living relatives, and trace fossils.

“The possibility that T. rex might have been as intelligent as a baboon is fascinating and terrifying, with the potential to reinvent our view of the past,” said Dr Darren Naish from the University of Southampton.

“But our study shows how all the data we have is against this idea. They were more like smart giant crocodiles, and that’s just as fascinating,” he added.