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Lystrosaurus

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Lystrosaurus was a unique genus of herbivorous dicynodont therapsids.

Lystrosaurus murrayi scale
Lystrosaurus murrayi scale

These animals lived during the late Permian and early Triassic epochs. This was approximately 248 million years ago. They are famous for surviving the Permian-Triassic extinction event. This event was the most severe mass extinction in Earth's history. Because they survived, Lystrosaurus thrived in the immediate aftermath. They became the most common terrestrial vertebrate fossils in Early Triassic beds. In some areas, they reached incredible levels of dominance.

Lystrosaurus skeleton
Lystrosaurus skeleton

In the Lystrosaurus Assemblage Zone of South Africa, they made up 95% of land vertebrates. This is the only time a single genus has dominated the Earth so completely.

As a dicynodont, Lystrosaurus had a very specific way of eating. It possessed only two teeth, which were a pair of tusk-like canines. The animal likely had a horny beak, similar to a turtle. It used this beak to bite off pieces of vegetation. The jaw joint allowed for a unique shearing action. Instead of moving up and down, the jaw moved backwards and forwards. This movement helped the animal grind food on a horny secondary palate. Because the jaw muscles were attached far forward on the skull, the face was short. This muscle placement also caused the eyes to be set high and well forward on the head.

Lystrosaurus murrayi 7
Lystrosaurus murrayi 7

The physical build of Lystrosaurus suggests it was a powerful digger. Its forelimbs were more robust than its hindlimbs. This strength likely helped it nest in burrows. The animal moved with a semi-sprawling gait. This means its legs were not directly under its body like a mammal's. Several skeletal features supported this movement. The shoulder blade, or scapula, was strongly ossified to help with stride length. The five sacral vertebrae, which connect the spine to the hips, were massive. These vertebrae were not fused, which made the back more rigid. This rigidity helped reduce sideways flexing while the animal walked.

Scientists have identified several different species within this genus.

Lystr murr1DB
Lystr murr1DB

While researchers once thought there were many more, only four to six species are currently recognized. Lystrosaurus maccaigi was the largest and most specialized species. However, it lived during the Permian and did not survive the extinction event. Lystrosaurus curvatus is considered the least specialized species. It is very important to scientists because it serves as a marker for the boundary between the Permian and Triassic periods. Other species include Lystrosaurus platyceps, L. oviceps, L. murrayi, and L. declivis. Some fossils from the Karoo Basin even suggest the animal had dimpled, leathery, and hairless skin.

Wegener fossils-mapped
Wegener fossils-mapped

The distribution of Lystrosaurus fossils provides vital clues about our planet's history. Fossils have been found in Antarctica, India, China, Mongolia, European Russia, and South Africa. The discovery of these remains in Antarctica was especially significant. In 1969 and 1970, Edwin H. Colbert and his team found fossils at Coalsack Bluff. This discovery helped support the theory of plate tectonics. It showed that these landmasses were once connected. The fossils proved that Lystrosaurus lived in areas that are now far apart but were once close together.

Lystr georg1DB
Lystr georg1DB

There are many theories about why Lystrosaurus survived the great extinction. One hypothesis involves the atmosphere. The extinction event may have reduced oxygen and increased carbon dioxide. Some researchers suggest Lystrosaurus survived because its burrowing lifestyle protected it from "stale air." They point to its barrel chest, which could hold large lungs, as an adaptation. Another theory involves a state called torpor. Torpor is a state similar to hibernation where an animal saves energy. Growth marks in the tusks of fossils found in Antarctica suggest they may have used torpor. This would be some of the oldest evidence of such a state in a vertebrate.

Lystrosaurus helps scientists understand the recovery of life after a disaster. While Lystrosaurus dominated, other animals like the therocephalians also survived. However, they were not as abundant. It took about 30 million years for the Earth's ecosystems to reach a complete recovery. The success of Lystrosaurus shows how certain biological traits can lead to massive success during times of change. By studying their bones and their environments, we learn how life adapts to a changing world.

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🖼️ Images & Media (6)
File:Wegener fossils-mapped.png
Wegener fossils-mapped.png
File:Lystrosaurus murrayi 7.JPG
Lystrosaurus murrayi 7.JPG
File:Lystrosaurus murrayi scale.svg
Lystrosaurus murrayi scale.svg
File:Lystr georg1DB.jpg
Lystr georg1DB.jpg
File:Lystr murr1DB.jpg
Lystr murr1DB.jpg
File:Lystrosaurus skeleton.jpg
Lystrosaurus skeleton.jpg
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