Permian Survivors
Summary: This focus from the perspective of two Lystrosaurus species as their ancestors witness and survive the Permian Extinction. Then it switches to the Early Triassic, in the Katberg Formation, South Africa of how they thrived and populated the earth.
Cast: Lystrosaurus murrayi and declivis, Myosaurus, Thrinaxodon, Broomistega, Galesaurus, Owenetta, Procolophon, Prolaecerta, Proterosuchus, Olvierosuchus, Lydekkerina, Micropholis, Kitchingnathus, Scaloposaurus, Tetracynodon darti, Moschorhinus, Promoschorhynchus, Ericiolacerta, Regisaurus, and Zorillodontops.
It starts off with Thomas behind a diorama exhibit display of an African savanna waterhole with herds of African Bush Elephants, Cape Buffaloes, and Masai Giraffes alongside a flock of Vulturine Guineafowls located in the African Diorama Hall of the Natural History Museum of Los Angeles. "One of the most eye-catching exhibits I like seeing in the museum is located here in the African Diorama Hall at the very end. This depicts a scene of an African waterhole where herds of animals gathered to wallow in the mud and drink during the dry season. These include herds of Cape Buffaloes, Towers of Masai Giraffes, The Tallest Land Animal on earth, flocks of Vulturine Guineafowl, and my favorite animals, is this herd of African Bush Elephants. But it got me thinking, how did mammals get their start? They were descended from early forms known as Synapsids, a transition form between reptile and mammal they dominate and diversified into many forms, but it didn't last forever until the Worst and largest Mass-Extinction Event, the earth has ever witnessed, the Permian-Triassic Extinction Event also called 'The Great Dying' which happened 251.9 million years ago leading to the extinction of 90% of the plant and animal species on Earth. The main cause of extinction was the large amount of carbon dioxide emitted by the flood basalt volcanic eruptions that created the Siberian Traps, which elevated global temperatures and acidified the oceans. But some organisms had survived, among them was this animal." He brings out a cast model of a dicynodont. "This is a Dicynodont, a relative to mammals known as Lystrosaurus, meaning "Shovel Lizard." Lystrosaurus was a heavily built, herbivorous animal, approximately the size of a pig. Lystrosaurus survived the Permian-Triassic extinction, and during the Early Triassic, they were by far the most common terrestrial vertebrates, accounting for as many as 95% of the total individuals in some fossil beds. This is the only time that a single species or genus of land animal dominated the Earth to such a degree in the absence of predators and herbivorous competitors, went on to thrive and re-radiate into a number of species within the genus, becoming the most common group of terrestrial vertebrates during the Early Triassic. Scientists and Researchers have offered various hypotheses for why Lystrosaurus survived the extinction event and thrived in the early Triassic. Among them going into a torpor state, it's burrowing life style, being semi-aquatic, or according to researcher, M.J. According to Benton, "Perhaps the survival of Lystrosaurus was simply a matter of luck". But how did they survive and how did they colonize the earth?"
. . . . .
The Katberg Formation in South Africa, 251.9 million years ago in the Late Permian. Morning dawns over a permian swamp with rivers running down covered with lush vegetation, herds of pig size animals browse and munched on the leaves with their beaks. These are Lystrosaurus consisting of the smallest Lystrosaurus murrayi and the larger Lystrosaurus declivis.
Lystrosaurus are dicynodonts more related to mammals than dinosaurs, As a dicynodont, Lystrosaurus had only two teeth which are a pair of tusk-like canines, and a horny beak that was used for biting off pieces of vegetation. Lystrosaurus was a heavily built, herbivorous animal, approximately the size of a pig. The structure of its shoulders and hip joints suggests that Lystrosaurus moved with a semi-sprawling gait. They were covered with dimpled, leathery and hairless skin. Their forelimbs were even more robust than the hindlimbs, and the animal is thought to have been a powerful digger that nested in burrows alongside the riverbanks. Their life was simple and peaceful, but on the other side changes are coming and in a bigger and destructive way.
In Siberia, a rumbling sound begins to grow. As it grows soon violent tremors ripple through the forests and scrublands. The ground begins to bulge and heat up. Far below the surface, a giant plume of molten rock rises from the mantle and begins piercing the Earth's crust. Magma bursts out of the ground, triggering pyroclastic eruptions that collapse the landscape around them. Animals in the immediate vicinity begin to panic. Suddenly, the ground implodes as a giant fissure some 32 km wide rips open, shooting out lava over 3000m into the air. Every living thing in the area is incinerated in a flash. In minutes, the region is transformed in a gushing sea of molten rock. This was the beginning of the Permian–Triassic Extinction Event, "The Great Dying." As the largest of the "Big Five'' mass extinctions of the Phanerozoic, it is the Earth's most severe known extinction event, with the extinction of 57% of biological families, 83% of genera, 81% of marine species and 70% of terrestrial vertebrate species.
The main cause of extinction was the flood basalt volcanic eruptions that created the Siberian Traps, which released huge amounts of carbon dioxide, elevating global temperatures and acidifying the oceans. The flood basalt eruptions that produced the Siberian Traps constituted one of the largest known volcanic events on Earth and covered over 2,000,000 square kilometers (770,000 sq mi) with lava (roughly the size of Saudi Arabia). Such a vast aerial extent of the flood basalts may have contributed to their exceptionally catastrophic impact. Volcanic activity occurred during a small number of high intensity pulses that exuded enormous volumes of magma, as opposed to flows emplaced at regular intervals. The rate of carbon dioxide release from the Siberian Traps represented one of the most rapid rises of carbon dioxide levels in the geologic record, with the rate of carbon dioxide emissions being estimated by one study to be five times faster than the rate during the already catastrophic Capitanian mass extinction event, which occurred as a result of the activity of the Emeishan Traps in southwestern China at the end of the Middle Permian. Carbon dioxide levels prior to and after the eruptions are poorly constrained, but may have jumped from between 500 and 4,000 ppm prior to the extinction event to around 8,000 ppm after the extinction according to one estimate. An estimate of pre-PTME carbon dioxide levels were at 400 ppm that then rose to around 2,500 ppm during the extinction event, with approximately 3,900 to 12,000 gigatonnes of carbon being added to the ocean-atmosphere system. As carbon dioxide levels shot up, extreme temperature rise would have followed, though some evidence suggests a lag of 12,000 to 128,000 years between the rise in volcanic carbon dioxide emissions and global warming. Global temperatures shot up to as much as 35 °C, and this hyperthermal condition may have lasted as long as 500,000 years. Air temperatures at Gondwana's high southern latitudes experienced a warming of ∼10–14 °C. Low latitude surface water temperatures skyrocketed by about 8 °C. So much carbon dioxide was released that inorganic carbon sinks were overwhelmed and depleted, enabling the extremely high carbon dioxide concentrations to persist in the atmosphere for much longer than would have otherwise been possible. There were consequences of the greenhouse effect on the marine environment being traced back to volcanic CO2 emissions. There were paired coronene-mercury spikes for a volcanic combustion cause of the mass extinction has also been found. The synchronicity of geographically disparate mercury anomalies with the environmental enrichment in isotopically light carbon confirms a common volcanogenic cause for these mercury spikes.
The emission of much additional carbon dioxide from the thermal decomposition of hydrocarbon deposits, including oil and coal, triggered by the eruptions, emissions of methane from the gasification of methane clathrates, emissions of methane possibly by novel methanogenic microorganism nourished by minerals dispersed in the eruptions, an extraterrestrial impact creating the Araguainha crater and consequent seismic release of methane, and the destruction of the ozone layer and increase in harmful solar radiation.
By now, the lava flows cover almost 100,000 km² at depths of nearly a kilometer. Dust, ash and sulfur released by the eruptions in Siberia rise high into the atmosphere and begin spreading around the world. In South Africa's Karoo Basin, they produce ominously-tinted sunsets spectated by grazing herds of Lystrosaurus for a time. Soon clouds of sulfurous gas and soot cut out sunlight and trigger a long volcanic winter across much of the planet. Then sulfur dioxide from the eruptions combines with water vapor in the atmosphere, creating deadly acid rain.
The Lystrosaurus retreated to their burrows for safety to wait it out. They have adaptations to survive the extinction,they are semi-aquatic and they enter a prolonged state of torpor analogous to hibernation. This could be the oldest evidence of a hibernation-like state in a vertebrate animal and indicates that torpor arose in vertebrates before mammals and dinosaurs evolved. Its burrowing life-style made it able to cope with an atmosphere of "stale air", and that specific features of its anatomy were part of this adaptation: a barrel chest that accommodated large lungs, short internal nostrils that facilitated rapid breathing, and high neural spines (projections on the dorsal side of the vertebrae) that gave greater leverage to the muscles that expanded and contracted its chest. However, there are weaknesses in all these points: the chest of Lystrosaurus was not significantly larger in proportion to its size than in other dicynodonts that became extinct; although Triassic dicynodonts appear to have had longer neural spines than their Permian counterparts, this feature may be related to posture, locomotion or even body size rather than respiratory efficiency. Being small they eat less than larger dicynodonts and after the extinction there is the lack of large predators.
Then, the nearby mountains and hills begin literally exploding in columns of ash and lava. Soon decades after the volcanic winter lifts, toxic elements like halogenated butane, methyl chloride and methyl bromide ravage the planet's Ozone layer. Animals and plants on the surface soon become exposed to lethal amounts of UV radiation. As centuries pass, volcanic CO2 builds up in the atmosphere, leading to intense global warming as the floodplains they inhabit begin drying out and as global temperatures rise dramatically, forest fires become more frequent and intense. The excess greenhouse gasses raise Earth's temperature by 5° C. On land, the deserts once confined to Central Pangaea begin to spread. In South Africa, the lush, wet, fertile landscape has shriveled into a power-dry, barren wilderness.
Coal deposits beneath the Siberian lava flows burn, releasing huge volumes of methane into the atmosphere. As temperatures rise further, freak firestorms and floods wash away topsoil into rivers and lakes. The nutrient runoff triggers toxic algae blooms which ravage freshwater ecosystems around the world. Worse still, oxygen levels in the atmosphere begin to plummet. Some 150,000 years after they began, the Siberian lava flows are now over a kilometer deep and cover an area nearly the size of Australia. As the eruptions continue, the last of Russia's old Permian fauna struggle for life in a toxic hellscape.
As millennia pass, the climate crisis extends beyond the land and begins invading the oceans. The increase in global temperatures changes the chemistry of the seas to the point where they lose oxygen. Marine life from crinoids and trilobites to sharks is suffocated as the water warms up to 104° F and turns anoxic. As the oceans turn anoxic, deadly pink/purple hydrogen-sulfide producing bacteria begin to thrive. Over thousands of years, the H2S spreads, poisoning the seas and killing off many groups of animals, including the trilobites. The influx of H2S spreads from the deep ocean into shallow seas, ravaging coastal ecosystems worldwide. In what's now Germany, both marine and terrestrial animals and plants are snuffed out as the poisonous gas collects along the coast.
As world temperatures rise and the oceans stagnate, vast quantities of methane hydrate buried far beneath the surface have rapidly begun to melt. Stagnant seas erupt as geysers of methane blast into the sky. Animals living in and around the coast are decimated as the air becomes unbreathable. Exposed to the air, the methane spontaneously ignites, setting the sky ablaze.
All over the world, methane erupts from the seas, causing global temperatures to skyrocket by another 5° C. With the influx of atmospheric methane, the world becomes 10 degrees hotter than it was before the crisis began. In Antarctica, a pair of Lystrosaurus murrayi watch from their burrow as a firestorm devastates the great Glossopteris forests.
A quarter of a million years into the climate crisis, life on Earth is on the brink of complete extinction. Weather systems are thrown out of whack by the increased temperatures. Powerful dust storms once confined to deserts grow to ravage large swaths of land. In eastern Russia, a violent sandstorm closes in on a rapidly diminishing lake. With the oceans so warm, hurricanes become more frequent and some develop into the most destructive weather phenomenon ever: hypercanes. And with the water oxygen-less and loaded with H2S, they spread their devastation far and wide. Poisonous fumes overtake them and they are washed away, along with countless other creatures. The hypercane leaves a trail of destruction across whole continents.
After half a million years, the Great Dying draws to a close. By now, the Siberian Traps eruptions have covered an area of over 7 million km² in lava over 4 million km deep. The climate chaos they unleashed has wiped out some 95% of all life on Earth. The largest mass extinction in the history of life. Only the hardiest species endure.
. . . . .
12,000 years Later
It is 251.902 million years ago in the Early Triassic, Immediately after the mass extinction, toxic bacteria thrive in the oxygen-depleted climate. Slimy mounds called stromatolites- made by cyanobacteria - cover the arid shoreline. In South Africa, the Lystrosuaurs have survived After the Great Dying, Lystrosaurus are among the first to repopulate the planet. They become so abundant that their numbers make up half of all life on Earth. For two million years, they flourish unhindered. But as life slowly recovers, other species begin to take hold. It takes life on Earth 10 million years to recover from the Great Dying. As it does, species adapt to the new world.
The Lysotrsuaurus herds feed on the plants, drinking in the river, wallowing in the mud, the smaller species of lystrosaurs scale up trees to find tender juicy leaves, and males fight with one another with their tusks and beaks over the right to mate with the females, and a sentry stands up on its hind legs and tail for balance on the lookout for predators. Although they are the most abundant and widespread land vertebrate at the time, they did share their land with other creatures, although the dinosaurs have yet to appear. One is a small dicynodont relative, Myosaurus meaning "Mice-like lizard." They do not possess tusks or postfrontal teeth of other dicynodonts, but just like Lystrosuarus, they were burrowers and even shared burrows with them. The burrows would have provided shelter from hot and cold temperatures because of their insulation qualities. They also may have been utilized by tetrapods to gain shelter from predators. Two types of burrows were made during the Triassic period. They were classified by their size by scientists as Type L (large) and Type G (giant) burrows. Tetrapods were hypothesized to have made Type G burrows; these burrows match the size and shape of Triassic tetrapods. The size of the burrows is closely correlated with the size of the creator. The stone deposits in these burrows also match the age of the tetrapod fossils found around it. The Type G burrows in Antarctica range from 8–19 cm in diameter. This size would have accommodated the Myosaurus well because it would have been the appropriate size to fit in these burrows.
The Burrows created by the Lystrosaurus often provided shelter for other creatures like the Thrinaxodon looking out from his burrow inside the burrow his mate is resting with eight suckling young that just hatched in a nest. It is a small cynodont synapsid roughly the size of a fox and possibly covered in hair. The dentition suggests that it was a carnivore, focusing its diet mostly on insects, small herbivores and invertebrates. Their unique secondary palate successfully separated the nasal passages from the rest of the mouth, allowing the Thrinaxodon to continue mastication without interrupting to breathe. This adaptation would have allowed the Thrinaxodon to mash its food to a greater extent, decreasing the amount of time necessary for digestion. Similar to other therapsids, Thrinaxodon adopted a semi-sprawling posture, an intermediary form between the sprawling position of basal tetrapods still observed in modern Crocodilians and the more upright posture present in current mammals. It is prevalent in the fossil record in part because it was one of the few carnivores of its time, and was of a larger size than similar cynodont carnivores like its next door neighbor the Galesaurus.
But this family has to share this burrow with a roommate. A Broomistega is an extinct genus of temnospondyl Rhinesuchid amphibia and during the Early Triassic the Karoo Basin was seasonally arid, so the Thrinaxodon may have been aestivating to conserve energy during a time when resource availability was low and the normally aquatic Broomistega may have entered to burrow to escape the hot and dry conditions of its environment. It could be a symbiotic relationship Thrinaxodon is able to dig burrows and it is carnivorous and could kill and eat Broomistega), but rather than kill the amphibian, the cynodont lets it live in its burrow. That's because the Broomistega has good vision and can see predators easily, and when you have your head in the hole you're digging you can't see predators behind you too well, so the Broomistega serves as a lookout for the Thrinaxodon and in return the Broomistega lets it live in its burrow. Modern amphibians like frogs have pretty good eyesight so Broomistega may have too, so perhaps it could have served as a sentry for the cynodont when it is digging and vulnerable.
On the rocks small lizard like reptiles like Owenetta, Kitchingnathus, and Procolophon bask in the heat of the sun to warm up their bodies. A lizard like archosaur known as Prolaecerta searches for insects. Prolacerta were considered to have been small, lizard-like animals. However, several cranial and postcranial features set Prolacerta apart from lizards and instead show that it is an early relative of crown-archosaurs. Some of these notable features include elongated cervical vertebrae with elongate, thickened neural spines, which gave Prolacerta a slightly elongated neck and a wide range of flexibility. Cranial features include the codont teeth, a feature observed in all ancestors of crown archosaurs, which were pointed and caniniform in shape. It was probably a small, active, terrestrial carnivore or insectivore due to its fang-like teeth of roughly the same size and shape. Prolacerta is considered to have been a quadruped, although due to its hind limbs being larger and longer than its front limbs, there is a possibility that it was habitually bipedal during high activity. Then the small reptiles ran off when it caught sight of a Regisaurus as it chased them to their burrows although most of them escaped into hiding in the burrows some created by the cynodonts and lystrosaurs. The Regisaurus manages to catch a Owenetta, luckily the Prolacerta escapes and finds himself at the riverbanks of the river.
He finds bugs in the most unlikely places, and has stumbled upon a bask of Proterosuchus. Proterosuchus is one of the earliest members of the clade Archosauriformes, which also includes crocodilians, pterosaurs, and dinosaurs, including birds, a mid-sized quadrupedal reptile with a sprawling stance that could reach a length of up to 3.5 meters (11 ft). It had a large head and distinctively hooked snout. It was a predator, which may have hunted prey such as Lystrosaurus. Like other crocopod archosauromorphs, Proterosuchus had a higher metabolic rate than extant ectotherms. Furthermore, Proterosuchus possessed fibrolamellar bone, indicative of a high growth rate and corresponding high metabolism. Its metabolic rate was lower than most other crocopods, except for the ectothermic phytosaurs and crocodilians, which may have been an adaptation to a crocodile-like predatory strategy. It had mesopic vision, indicating that it was adapted to see well in both bright and dim light. Mesopic vision is characteristic of cathemeral animals, which are active in both night and day, and crepuscular animals, which are active in twilight. Adaptations to see in dim light may have been ancestral to archosaurs, and Proterosuchus may have been an early example of this , Proterosuchus lived near the Antarctic Circle, so its mesopic vision may have instead been an adaptation to the highly seasonal day lengths it experienced. The hearing of Proterosuchus was likely adapted for lower frequencies, as in modern crocodiles. Due to its low-sensitivity hearing, Proterosuchus probably did not rely heavily on vocal communication and may have been relatively solitary. Based on the size of its olfactory bulbs, Proterosuchus had a strong sense of smell, similar to that of modern crocodiles. The herd of Lystrosaurus lie down next to the bask of Proterosuchus as the Prolacertia have found more choices to dine on bugs from. Normally they are enemies as predators and prey, but there are neutral zones where these two animals can live alongside one another without harm.
As the Prolacertia feast on the bugs, but it attracts other predators, one is snatched by a Lydekkerina. It was a stereospondyl temnospondyl while most other stereospondyls were semi aquatic, Lydekkerina was exclusively terrestrial. It also attracts Tetracynodon which are related mammals that feed on insects and small vertebrates like the Prolacertia. Another small predator, a therapsid known as Ericiolacerta comes in to snatch on the bugs. But it has disturbed the Lystrosuaurs who bellow and charge at the small predators and Proterosuchus to hiss and snap at them causing them to run off. Nearby is a gathering of Micropholis they have come here to mate, the males mount on the larger females the male places a sperm packet called a spermatophore on the ground or on debris in a pool. The female inserts it into her cloaca to fertilize her eggs, which she may attach to sticks and leaves or under rocks.
Soon night falls as the Lystrosuaurs and other creatures return to their burrows to sleep for the nights, while others like the cynodonts who are nocturnal this is their time to come out and hunt. A Lystrosaurus is lagging behind due to injuries from a fight with another male Lystrosuaurs and it has attracted the attention of another predator. Stalking among the rocks and foliage is a Moschorhinus, the top predator of the Karoo. It was a large carnivore, reaching 1.5 m (4.9 ft) in total body length with the largest skull comparable to that of a lion in size. It had a broad, blunt snout which bore long, straight canines. It appears to have replaced the gorgonopsids ecologically, and hunted much like a big cat. While most abundant in the Late Permian, it survived a little after the Permian Extinction, though these Triassic individuals had stunted growth.
It slowly approaches the Lystorsuaurs and charges to attack. Moschorhinus was able to pierce skin and hold onto struggling prey with its long canines. This is the first record of this kind of hunting technique. Given its sturdily designed, thick snout, enormous canines, and powerful jaw muscles, Moschorhinus appears to have been a daunting predator. As it attacks the Lystrosaurus it tries to fight back with its feet, sharp beak, and tusks, but it was too weak to fight back and succumbs to his demise. The Moschorhinus feasts on his kill, but it has attracted the scavengers. Soon Packs of Scaloposaurus, Promoschorhynchus, and Zorillodontops gathered around the carcass waiting their turn to feast on the carcass. Once the Moschorhinus has finished his fill and leaves, the scavengers eat what's left and among them a Olvierosuchus snags a leg from the carcass. Unlike other akidnognathids such as Moschorhinus, it has a narrow snout and fewer postcanine teeth. She brings it back to her burrow which is straight and wide and includes an entry ramp and living chamber. It is here she stores her food which she will eat for later.
The next morning, the Lystrosaurus emerged from their burrows to start the day again. They are true Permian Survivors dominating the earth and diversifying into different species in which some would grow to large proportions. But by the end of the Triassic, they will be all gone and another creature known as the dinosaurs will fill in the shoes left by the lystrosaurs.
Trivia/References:
-The Name is meant to reflect the success of Lystrosaurus surviving the Great Dying Extinction and diversifying and populating the earth during the early Triassic.
Speculative Behaviors:
-The Thrinaxodon pair is based on the first episode of Walking with Dinosaurs, their models provided the bases of the unnamed Cynodont for the episode.
-The Thrinaxodon living with a Broomistega is based on an artwork by Olmagon titled "Digger Buddies", the relationship is based on the pistol shrimp and goby fish, and based on fossil evidence.
-The Lystrosaurus burrows providing shelter for other animals as a keystone species similar to the Giant Armadillo
-The Lystrosaurus basking next to a Proterosuchus is based on Capybaras and Caimans to show not all predators would attack prey on sight.
-Some of the information is inspired by Rahonavis70m's take on a Walking with Dinosaurs Sequel.
-Prolacerta eating insects off of Lystrosaurus and Proterosuchus is based on the agama lizards and lions and the lizards and Tarbosaurus from "Prehistoric Planet."
-Micropholis mating behavior is based on salamanders and frogs.
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The Next Story is "Long Neckin' Love" which follows a bachelor herd of different species of Mamenchisaurus who are drawn from the forests to an open plain where they are gathered to court and fight for the right to mate.
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