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Tuesday, September 15, 2015

The evolution track of the Ankylosaurus tail

One of the most impressive weapons that appeared during the Cretaceous Period dinosaur arms race is a big mace head belonging to some group members plant eaters.

Results of a new study published in the Journal of Anatomy this week showing the steps of evolution of the features typical of heavily armed dinosaur Ankylosaurus and cousin, mace even ferocious Tyrannosaurus rex could give reason for concern.

The researchers studied the fossils of a group called Ankylosaurus, including nightstick or mace early primitive species without the tail and the latter with the tail fully developed.
Gobisaurus (top) compared with Ziapelta, an ankylosaur with a fully developed tail club, as seen in an undated illustration courtesy of Victoria Arbour. (Picture from: http://reut.rs/1i502UU)
Ankylosaurus tail evolution mace start much earlier than previously thought, according to research findings, and the mace was changed in two steps over tens of millions of years.

First, the vertebrae in the back of the tail is changed so that the tail becomes rigid. Then the bones are formed in the skin as body armor, called osteoderm, becomes very large at the end of the tail and completely enveloped the tail end to form a mace that can be swung to the enemy.

Ankylosaurus lived at a time when the largest land predators in Earth's history such as T. rex roamed, ripping other dinosaurs with powerful jaws and sharp teeth.

In the arms race, few plant-eaters to develop weapons of defense.

"The tail mace clearly an effective weapon and could break an ankle predator," paleontologist Victoria Arbour from North Carolina State University and the North Carolina Museum of Natural Sciences who led the study.

"But the animals were alive today, guns are also often used against their own species - like horn sheep and rusa-- so maybe Ankylosaurus do the same thing."

Ankylosaurus dinosaur is a wide body with four legs covered plates and spurs hard. The oldest known Ankylosaurus lived about 160 million years ago during the Jurassic Period, Arbour said.

The first tail mace seen already fully formed about 75 million years ago during the Cretaceous Period.

Ankylosaurus with a length of approximately six meters is the biggest and the last Ankylosaurus, live at the end of the dinosaurs about 65 million years ago.

Ankylosaurus from China is very important to understand the origin of the tail mace, including Gobisaurus, from the period around 92 million years ago, and Liaoningosaurus, from about 122 million years ago, explains Arbour as reported by Reuters news agency. *** [EKA | FROM VARIOUS SOURCES | REUTERS]
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