Introducing the Abydosaurus

 

FOSSIL HUNTERS have done it again, unearthing a previously unknown species of dinosaur. This find is particularly valuable, however, given that the discovery includes four skulls – two of them intact – of one of the giant plant-eating dinosaurs, writes DICK AHLSTROM, Science Editor

Complete skulls of the massive sauropods, the long-necked plant-eaters that include the Brachiosaurus, are very rare in the fossil record. While their heavy leg bones and vertebrae readily formed intact fossils, their skulls were surprisingly thin and fragile for such large beasts. Thus few skulls survive for study today.

Details of the find, made at a quarry in the famous Dinosaur National Monument in eastern Utah in the US, were published in the current issue of Naturwissenschaften (Science of Nature), a Springer title.

The new animal is known as Abydosaurus and was located embedded in tough sandstone in the monument’s Cedar Mountain Formation near Vernal, Utah. Palaeontologists ended up using explosives to release the fossils from the stone.

Scientists were able to date the fossil skulls by analysing mineral crystals of zircon found in adjacent rocks, according to Dr Brooks Britt, a palaeontologist at Brigham Young University who worked on the project. This dates Abydosaurus to having lived about 105 million years ago.

Dr Britt says that the skulls are from juveniles estimated to be around 7.6 metres (25 ft) long. Other bones found nearby, including vertebrae, suggest, however, that the mature Abydosaurus was “substantially larger” and could have matched Brachiosaurus for size, about 25 metres long. Brachiosaurus roamed the land much earlier, about 150 million years ago. While the scientists were delighted to have found a new species of dinosaur, equally important is the fact that two of the four skulls are intact. Complete fossilised sauropod skulls are almost never found because they are surprisingly fragile. Palaeontologists hold complete skulls for only eight of the 120 known species of these animals.

They had tremendously heavy bodies and sturdy legs that helped to counterbalance their very long necks. Light skulls were an advantage given this body shape, says Dr Britt. “Their heads are built lighter than mammal skulls because they sit way out at the end of very long necks.”

The skulls were thin and lightly held together with tissues that did not fossilise well. “Instead of thick bones fused together, sauropod skulls are made of thin bones bound together by soft tissue. Usually it falls apart quickly after death and disintegrates,” Dr Britt says.

The find gives useful evidence about how the animals, some of the largest to have walked the earth, managed to keep themselves so well fed. It all seems to have been quite uncomplicated, Dr Britt suggests.“They didn’t chew their food, they just grabbed it and swallowed it. The skulls are only one two-hundredth of total body volume and don’t have an elaborate chewing system.”

The Abydosaurus sported a classic form of sauropod teeth, long narrow pencil points that were useful for stripping tough greenery off the branches and dispatching it with little or no chewing. The business of reducing the food was better handled further down the animal’s alimentary canal where the near indigestible roughage could be broken down and digested.

In the Jurassic Period – between 206 and 144 million years ago – sauropods showed a widerange of tooth shapes, but by the end of the dinosaur age 65 million years ago all sauropods had these pencil-like teeth.

The new dinosaur’s full name is Abydosaurus mcintoshi. The skull was found in a quarry overlooking the Green River, so took the name Abydos from the Greek name for the city along the River Nile (now El Araba el Madfuna) that was the burial place of the head and neck of the Egyptian god, Osiris. Sauros is the Greek word for lizard and the “mcintoshi” honours American palaeontologist Jack McIntosh for his contributions to the study of sauropods.

– Additional reporting: PA