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Wonky skull of Styracosaurus leads paleontologists to question earlier identifications of species

Wonky skull of five-meter-long Styracosaurus named ‘Hannah’ with a range of long horns leads scientists to question the previous theory that all dinosaurs had symmetrical faces

  • The intact Styracosaurus skull has horns and was discovered in Canada
  • Asymmetrical face suggests more morphological variability than expected
  • Scientists fear that incomplete skulls have been wrongly classified as new species

New analysis of the skull of a Styracosaurus has led scientists to question an earlier theory that all dinosaurs had symmetrical faces.

The well-preserved skull was discovered in 2015 by Scott Persons – then a graduate student at the University of Alberta – during an expedition in the badlands northwest of Dinosaur Provincial Park in Canada.

The skull is from a Styracosaurus – a horned dinosaur more than five meters long with a range of long horns that walked the earth about 75 million years ago.

The specimen was nicknamed Hannah, after the dog of Persons.

Paleontologist Scott persons, depicted next to the partially exposed skull

Paleontologist Scott persons, depicted next to the partially exposed skull

Analysis of the skull by paleontologists at the University of Alberta has now shown that the horns of the Styracosaurus were asymmetrical.

This has important implications for how paleontologists identify new types of dinosaurs.

“When parts of a side of the skull were missing, paleontologists assumed that the missing side was symmetrical with the side that was preserved,” says Personen.

“It appears that this is not necessarily the case. Nowadays, deer often have left and right antlers that differ in their branching patterns.

“Hannah shows dramatically that dinosaurs can be the same way.”

Hannah's asymmetrical skull seen from all sides. It is not known whether the Styracosaurus was a woman but was about five meters long

Hannah's asymmetrical skull seen from all sides. It is not known whether the Styracosaurus was a woman but was about five meters long

Hannah’s asymmetrical skull seen from all sides. It is not known whether the Styracosaurus was a woman but was about five meters long

Nickname Hannah, the dinosaur was a Styracosaurus - a horned dinosaur more than five meters long with a range of long horns Nickname Hannah, the dinosaur was a Styracosaurus - a horned dinosaur more than five meters long with a range of long horns

Nickname Hannah, the dinosaur was a Styracosaurus – a horned dinosaur more than five meters long with a range of long horns

The differences in the left and right halves of the skull are so extreme that if the paleontologists had only found isolated halves, they might have concluded that they belonged to two different types.

Hannah shows that the pattern of dinosaur horns can vary considerably, meaning that some fossils that were once thought to be unique species need to be reassessed.

“The skull shows how much morphological variability there was in the gender,” said Robert Holmes, professor of Biological Sciences, who led the study.

How many dinosaur species existed?

About 700 valid dinosaur species have now been discovered and named – with about 300 genera.

Scientists predict that there were many more because the fossil record is incomplete.

Fossils are not available for all periods of history due to some centuries of rock carried from the earth’s surface, such as the Middle Jurassic era.

Many dinosaurs from the late Cretaceous period have been discovered.

Existing species are incredibly varied with some dinosaurs weighing eight tons, while others weigh just eight pounds.

Source: American Museum of Natural History

It is a tradition for the finder to nickname the discovery, Mr Persons decided to name it after his dog Hannah.

“She’s a good dog and I knew she was home and missed me while I was on an expedition,” he said.

It is not known whether the fossil is really feminine.

Researchers gathered more information about the fossil by collaborating with researchers Ahmed Qureshi and graduate student Baltej Rupal from the Faculty of Engineering who carried out a 3D laser scan of the skull.

Mr. persons said: ‘That made our publication contain a digital reconstruction, with which scientists all over the world can download the 3D model and inspect it in detail.

“This is the future of paleontological collections: digital dinosaurs.”

“Morphological variation and asymmetrical development in the skull of Styracosaurus albertensis,” was published in the magazine Chalk investigation.

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