Borealopelta

Chapter • Meet the dinosaur

Overview

Borealopelta markmitchelli is one of the best-preserved dinosaurs ever found. It was a nodosaurid – an armoured dinosaur without a tail club – roughly five metres long and weighing a little over a tonne. Its back and flanks were covered by hundreds of bony plates called osteoderms, which in this specimen remain in life position together with the keratin sheaths that once covered them. A pair of long, forward-angled spines rose from the shoulders, the largest around half a metre long. The body was broad and low-slung, the limbs stout, and the head small with a narrow, beaked snout. The most remarkable thing about the fossil is that its colour could be analysed. Chemical traces of the pigment pheomelanin in the preserved skin indicate that Borealopelta was reddish-brown above and paler beneath – a pattern known as countershading, common today in prey animals. That a one-tonne armoured animal still needed camouflage says a great deal about the predators of Early Cretaceous North America; large allosauroids such as Acrocanthosaurus shared the same landscape. The stomach contents are preserved as well, which is exceptionally rare. Analysis shows that the animal's last meal was almost ninety per cent ferns, dominated by a single type, with conifer material making up only a few per cent. The gut mass also contained charcoal, suggesting that Borealopelta was browsing in a landscape recovering from a wildfire, where ferns had quickly colonised the ground. It is one of very few dinosaurs for which we know what a single individual ate on its final day. The fossil was found by accident on 21 March 2011 by a shovel operator at Suncor's Millennium oil sands mine north of Fort McMurray, Alberta, Canada. The animal had died near the coast, floated out into the Western Interior Seaway and sunk back-first to the sea floor, where mud buried it quickly. Preparator Mark Mitchell of the Royal Tyrrell Museum spent roughly 7,000 hours freeing the specimen from the rock-hard marine siltstone – work honoured when Caleb Brown and colleagues named the species in 2017.

Chapter • Where it lived

Habitat

Borealopelta lived about 110–112 million years ago, during the Albian stage of the Early Cretaceous, in what is now northern Alberta, Canada. The landscape was a coastal lowland of floodplains at the edge of the Western Interior Seaway, with conifer forests and wide fern-covered ground. The only known specimen came from the Clearwater Formation in Suncor's Millennium Mine north of Fort McMurray – marine sediments into which the carcass drifted after death. The fossil is now on display at the Royal Tyrrell Museum of Palaeontology in Drumheller.

Chapter • Wild behavior

Behavior & Ecology

Did you know?

Chapter • Scientific place

Taxonomy