Palaeontologists – including a citizen scientist – have uncovered fossil evidence for a community of meat-eating dinosaurs in southeast England dating to 135 million years ago.

The discovery marks the first time tyrannosaurs have been found in rocks of this age and location.

In addition to Tyrannosaurus rex relatives, the University of Southampton researchers identified teeth belonging to spinosaurs and dromaeosaurs. All three groups are predatory dinosaurs known as theropods.

“These East Sussex dinosaurs are older than those from the better-known Cretaceous sediments of the Isle of Wight,” says co-author Darren Naish. (The Isle of Wight is a fossiliferous island in the English Channel.)

“[The East Sussex dinosaurs] are mysterious and poorly known by comparison. We’ve hoped for decades to find out which theropod groups lived here, so the conclusions of our new study are really exciting,” adds Naish.

The researchers identified the predators in this early Cretaceous ecosystem thanks to retired quarryman, Dave Brockhurst, who spent 30 years collecting fossils from the Bexhill-on-Sea region of East Sussex.

Brockhurst collected over 5,000 fossils and yet theropods were represented by only 10 or so teeth.

“Dinosaur teeth are tough fossils and are usually preserved more frequently than bone. For that reason, they’re often crucial when we want to reconstruct the diversity of an ecosystem”, says lead author Chris Barker.

Theropod teeth are highly functional, so evolution has selected for variations in the size, shape, and anatomy of their serrated edges. The researchers used a combination of techniques, including machine learning, to compare and classify the teeth based on their variations.

“Assigning isolated teeth to theropod groups can be challenging, especially as many features evolve independently amongst different lineages” says co-author Lucy Handford. “This is why we employed various methods to help refine our findings.”

Identifying tyrannosaurs from a new site deepens our understanding of the region during the early Cretaceous period. The tyrannosaurs would have been about a third of the size of a T. rex and likely hunted small dinosaurs and other reptiles in the floodplain habitat.

“This project shows that museum collections, curators, and collectors are vital for pushing forward our understanding of the diversity of dinosaurs, and other extinct groups,” says project supervisor Neil Gostling.

The research is published in the journal Papers in Palaeontology.