Monsters of the Permian period lie in wait at museum
million years ago, amphibians were the top predators. Temnospondyli resembled large crocodiles and comprised several groups, some of which became adapted to living on the land. When land-dwelling carnivores evolved, they preyed on and gradually reduced the number of amphibians.
During the Permian, reptiles began to dominate the land. They evolved into many forms, from sabre-toothed flesh-eaters to large plant-eaters. The Permian reptiles can be classified into three groups based on the number of holes in their skulls; the synapsids, the anapsids and diapsids. The synapsids have a single hole in the skull behind each eye; they are ‘‘mammal-like reptiles’’ because they showed mammal-like characteristics which had not fully evolved. Synapsids are divided into two groups, the pelycosaurs and the therapsids. The therapsids evolved into many forms and dominated the late Permian, 260-250 million years ago.
They are thought to be the ancestors of modern mammals. The exhibition has a model of the intimidating top predator of the time, the three-meter-long, meateating therapsid Inostrancevia.
The second group, the anapsids are distinguished by the absence of a hole in the skull behind each eye, turtles are believed to be descended from Permian anapsids. There is a model of the brutal looking anapsid reptile, Scutosaurus. The third Permian reptile group, diapsids, have two holes in the skull behind each eye.
During the Permian, diapsids were small and inconspicuous but they are ancestors to snakes, lizards, crocodiles, birds and dinosaurs.
A little over 250 million years ago the Earth suffered the worst disaster of all time, the Permian mass extinction. Forests disappeared, not to return for 5 million years; up to 96 per cent of all marine life and 70 per cent of reptile, amphibian and plant species were lost.
There were a number of causes. A massive and extended series of volcanic eruptions which caused the Siberian Traps (from the Scandinavian word for stairs ‘‘trappa’’) continued for one million years and covered an area the size of western Europe in basalt. The volcanoes caused acid rain and blocked out sunlight which disrupted photosynthesis and resulted in the collapse of the food chain. Huge amounts of carbon dioxide erupted by the volcanoes initiated global warming. Large amounts of methane gas were released into the atmosphere when the rising temperatures began to melt frozen methane-hydrate, stored in large deposits beneath the ocean floor.
Methane is a greenhouse gas and the more methane that was released the warmer the Earth became which caused more methane to be released – a runaway greenhouse effect, eventually adding 10 degrees Celsius to the average temperature of the Earth, wiping out the vast majority of species.
There were survivors; they tended to be small to medium-sized animals that may have been burrowers and were able to cope with the extreme temperatures of the planet. One of these, a therapsid (one hole behind each eye), mammal-like reptile, cynodont, is believed to be our mammalian ancestor.
‘‘Permian Monsters – Life Before Dinosaurs’’ is on until September 9, 2018.