Things everybody “knows” about Stegosaurus

Myth Stegosaurus had a second brain in its hips.

Fact No dinosaur had a second brain. Smithsonian Magazine: The double dinosaur brain myth, 2012 The leading idea is that the hip space held a glycogen body, like birds have, though what it does is still unclear. Smithsonian Magazine: The double dinosaur brain myth, 2012

Myth Stegosaurus had eight tail spikes.

Fact Marsh’s 1891 skeleton drawing had eight tail spikes, a mash-up of several specimens. There is no evidence for any number other than four. Smithsonian Magazine: The myth of the eight-spiked Stegosaurus, 2011

Myth The plates lay flat, like a turtle shell.

Fact Marsh first thought the plates lay flat. A mud-covered specimen later showed they stood upright. Natural History Museum: Stegosaurus (Dino Directory) The plates stood upright, alternating on either side of the spine. Natural History Museum: Stegosaurus (Dino Directory)

Myth The spikes were on its wrists.

Fact In 1880 Marsh suggested the spikes were on its wrists. Smithsonian Magazine: The myth of the eight-spiked Stegosaurus, 2011 A quarry sketch from collector William Reed showed spikes at the tail tip. Marsh changed his mind by 1887. Smithsonian Magazine: The myth of the eight-spiked Stegosaurus, 2011

Myth The plates were armour.

Fact Defence is now out of fashion, because the plates, though large, are thin and fragile. Natural History Museum: A Stegosaurus brought to life An AMNH curator points out the plates were only loosely attached, so may not have stood up to a predator’s bite. American Museum of Natural History: Apex Stegosaurus fossil and “11 Questions About Stegosaurus”

Myth Stegosaurus fought T. rex.

Fact Stegosaurus lived about 150 million years ago and T. rex about 70 million years ago, so we live closer in time to T. rex than Stegosaurus did. American Museum of Natural History: Apex Stegosaurus fossil and “11 Questions About Stegosaurus” Humans and Stegosaurus missed each other by over 140 million years. Smithsonian Magazine: Watch out for that thagomizer!, 2011

Myth “Thagomizer” is the official science name.

Fact “Thagomizer” isn’t an official science term: palaeontologists also just say tail spikes. American Museum of Natural History: Apex Stegosaurus fossil and “11 Questions About Stegosaurus”

Myth Sophie was a female.

Fact Sophie’s sex is unknown: the name doesn’t mean it was female. Maidment, Brassey & Barrett (2015), The postcranial skeleton of an exceptionally complete individual of Stegosaurus stenops, PLOS ONE

Myth Its brain was the size of a walnut.

Fact Its head was small, and its brain was around the size of a plum, says the Natural History Museum. Natural History Museum: Stegosaurus (Dino Directory) An AMNH curator compares the brain to a small lemon or lime. American Museum of Natural History: Apex Stegosaurus fossil and “11 Questions About Stegosaurus”

Myth Stegosaurus lived in big herds.

Fact The Natural History Museum says Stegosaurus didn’t live in herds: probably alone or in small groups. Natural History Museum: Stegosaurus Q&A with Prof Paul Barrett A 2015 study described a Montana quarry where at least five plated stegosaurs were buried together, which possibly suggests they were social. Saitta (2015), Evidence for sexual dimorphism in the plated dinosaur Stegosaurus mjosi, PLOS ONE