Prehistory of Great Lakes Earth
In The Beginning…
Right from the start, Great Lakes Earth proved itself to be different from our own.
At least six billion years ago, what would become the solar system of Great Lakes Earth was once a cluster of dwarf planets slowly drifting aimlessly into space. This cluster would have been a dark, crowded mass of spheroids made of either rock, ice or metal and varying in diameter from 600 to 2500 miles. How this cluster came to be or when it first came to be remains a mystery. Surrounding the cluster on all sides were more organized systems of planets and moons orbiting supergiant and even hypergiant stars, hot, bright bodies many times larger than what would one day be the sun. According to basic astronomy, larger stars have shorter lifespans, so none of the neighboring stars would have exceeded a lifespan of 100 million years. When they went nova, the cluster would have been bathed in a nebulous mass of hydrogen, helium, iron and heavier elements.
By 5,050,000,000 years ago, the nebula had accumulated enough for gravity to gather round and create a protostar. 50 million years later, a yellow G-type main-sequence star became the center of the cluster’s mini-universe. The sun was born. Unfortunately, the birth of the sun would have violent results.
The sun’s newly-found gravity had transformed the dwarf planets of the cluster from a mass collection of aimless wanderers into a spinning demolition derby. For the first 100 million years, the planets would crash into each other, only to have their cores merge together into new ones, aiding to the accretion process. Alternate Earth 111 was no exception. 100 million years of repeated crashing and remerging created a seasonably tilting, spherical jigsaw puzzle eight thousand miles wide and 25,000 around concealing a 760-mile-wide core rich in iron, nickel, potassium, uranium, sulfur, silicon, aluminum, magnesium, carbon and thorium. In the process, its increasing gravity would have caught a dwarf planet 3300 miles wide and 200 billion tons, the dwarf planet that would become the moon of Great Lakes Earth.
But just as the planet had reached its modern size and captured its sole natural satellite, fate would not allow the newly-molded Great Lakes Earth to rest on laurels — not yet, at least.
From 4.9 to 4.4 billion years ago, all of the new planets had used their gravities to capture all that remained of the dwarf planets that died during the accretion process — pieces of rock, metal and ice varying in size from a couple feet to a thousand miles in diameter. The resulting bombardment would have been unrelenting. How much so?
Let us imagine the annual rainfall of Buenaventura, Colombia — 6,275.6 millimeters — being the global daily forecast for the next 500 million years…if the rain were space garbage instead of water.
After 500 million years, the chaos had finally subsided. The ice accumulated over the millions of years became both liquid water on the surface and water vapor in the atmosphere, the combination conspiring to create the oceans of Great Lakes Earth. As soon as the bombardment stopped, life had the chance to evolve, but the world it would start in would be hostile to us. 95% of the planet’s surface was a vast ocean, with the rest being basaltic islands that could not keep up against the constantly pounding waves. Carbon dioxide made up a quarter of the planet’s atmosphere, turning the atmosphere a vivid blood-red. And the global ocean was so full of iron that it would have glowed a deep, dark-green sheen. Yet, this is where and when the first single-celled organisms would have thrived. They would have been photosynthetic, absorbing energy from sunlight and turning carbon dioxide into food.
Four billion years ago, the global ocean was being challenged. A new kind of rock popped out of the surface that combined toughness with lightness. This rock was granite, but not OUR granite. The crystals of quartz, mica, diamond, graphite and feldspar would have averaged seven feet in length. The only way for these crystals to be so big is if the granite that created the continents cooled down very slowly before breaching to the surface. The longer it takes a granite boulder to cool, the larger the crystals and therefore the more resistant the rock itself. Four billion years ago, there could be 86 granitic landmasses worldwide.
At the same time, as new species of microbes rose and fell, one particular group improvised on the photosynthesis process and released oxygen as waste material. This gave rise to the atmosphere that later, more multicellular, life-forms would find breathable. Not just that, but they had also evolved a major piece of cellular anatomy — the mitochondrion, a sausage-shaped library of the genetic structure. This gave rise to the eukaryote, the multicellular organism who had more specialized cellular structures than bacteria. As time went on, these enterprising newcomers spiced up the fun of creation by inventing sex. (We don’t know why these creatures stopped dividing in two, or how they came to this idea.)
By three-point-six billion years ago, all the shallow waters in the world still glowed green. How could that be? A closer look shows a different source of green. In the shallows of the continental shelves, there was a dense crowding of mounds one meter long, wide and tall. These were stromatolites, created by the annual accretion of algal bacteria. In time, their photosynthetic tendencies oxidized the oceans from green to blue.
By one-point-three billion years ago, multicellular creations were everywhere. Wherever you go, you’d no doubt find handfuls of species of bacteria, algae, fungi, amoeba and harosans. The algae and fungi had colonized and carpeted all 50 landmasses, having fused from the original 86 granitic mini-continents. The only way for this to be possible is if the atmosphere had created a shield against the harmful ultraviolet radiation from the sun. Turns out, the colonization of algae and lichens — the symbiotic relationships between algae and fungi — matched the timing for the formation of an ozone layer. In the lichen relationship, the algae absorbed sunlight and turned it into sugars, and the fungi, in turn, absorbed minerals from the rocks, creating a layer somewhat similar to soil. Imagine the green fields of Laki on the ultimate macrocosm.
But life was about to be put to the ultimate test.
For one-point-three billion years ago, carbon dioxide in the atmosphere had hit a record low, thanks to the onslaught of photosynthesizers, and that could mean only one thing — a major ice age. So major, in fact, that all of the continents and their shelves would be buried under a mile of ice, leaving the deeper, more volcanically active (therefore warmer) ocean depths liquid for at least half a year. The mean surface temperature had dropped from 86 degrees Fahrenheit to 41. Complex life had just arrived, and already they suffered the worst catastrophe in history. The lucky few became the forerunners of all plant and animal life. But this wonder of evolution would have to wait a very long time.
A similar event happened in our geologic history, an event geologists called Snowball Earth, where it was hypothesized that from 720 to 635 million years ago, Earth had been encased in ice not once but twice. The one difference between our Snowball Earth and their Snowball Earth is that on Great Lakes Earth, there was only one snowball.
750 million years ago, the seafloor began to speed up, raising sea levels. Volcanoes belched from beneath the surface, warming the planet. As the sea level rose, so did global temperature, and the final straw that made the melting absolute was the global supply of frozen methane, which were extremely sensitive to temperature changes, melting into an explosive greenhouse gas. This melting further rose global temperatures and sea levels.
Immediately after the ice melted, a second wave of green algae colonized the freshly carved coastlines and the lands were once again carpeted with fungi. Over millions of years, those algae would evolve into the first plants, though they would be bryophytical, resembling mosses, hornworts and liverworts.
Beneath the surface, the surviving lifeforms proliferated into higher numbers of species, but they consisted only of the simplest lifeforms imaginable — sponges, worms, jellyfish, hydrae and strange, alien lifeforms loosely called “Ediacarans”, ranging from the disk-like Dickinsonia to the leaf-like Charnia. Also, from 720 to 600 million years ago, the rate of evolution was so sluggish that, on average, one old species would evolve into one new species every five to ten million years. This puzzles scientists. The ozone layer was already well-established, so the animals could have colonized the land almost immediately. They certainly were lagging behind as the plants and fungi colonized and diversified on land. Maybe the Ediacaran fauna was just an ecological trial run, an easy start to what would later evolve into more and more complex ecosystems.
Whatever the reason, that all changed during the Cambrian Explosion 600 million years ago. The gradual creation of new species suddenly went on the accelerator, and new shapes appeared geologically quicker than you can write a dot on a sentence. Now, one new species could branch out into a dozen new ones every one million years.
The new bodies were no longer soft, but rigid and armored. Predators took their first taste for animal flesh. The Cambrian Explosion 600 million years ago witnessed the beginnings of the arthropods (the group that includes crabs, spiders and insects), the echinoderms (the group that includes stars and urchins), the mollusks (the group that includes snails, octopus and shellfish), the brachiopods (shells that open up and down, rather than left and right like on the mollusks), the bryozoans (“moss animals”) and even the earliest chordates (animals with a backbone).
On the surface, meanwhile, the first stemmed plants took root, resembling Cooksonia (perhaps being Cooksonia.) After millions of years of clinging on to riverbanks and coastlines, they had started to evolve two types of transport tissues that would prove vital in the future — the xylem (transports water and nutrients from the roots to the shoots and leaves) and the phloem (transports the soluble organic compounds made during photosynthesis to all of the plant’s essential areas). This vascularization would prove vital to the future creation of plant-based ecosystems. To add to their success, they had exchanged spore germination for a more efficient kind of embryo — the seed. It was protected by a hard, outer shell, shielding the vital insides from most if not all outside elements, an advantage that the spores of fungi and non-vascular plants sorely lacked.
Some of the most alien inhabitants of Great Lakes Earth during the Cambrian are identical to the creatures we had found in the Burgess Shale in British Columbia, Canada. The most creepy-looking was the yard-long Anomalocaris, who hunted some of the other life forms via grasping claws growing from its face that resembled arms.
The three-inch long Opabinia resembled Anomalocaris, except that it had a proboscis longer than its body and resembling the nozzle of a vaccuum cleaner.
But perhaps the most alien of the Cambrian animals was a lobopod named Hallucigenia. Though barely an inch long, its eight pairs of clawed legs and conical spines above each pair gave it true distinction.
Oddly enough, for whatever reason, the most basic of Cambrian creatures — the urchin-like Wiwaxia, spiny Orthrozanclus, flat Odontogriphus and the sponge-like archaeocyathids — never existed on Great Lakes Earth, and no one knows why.
489 million years ago, the Cambrian gave way to the Paibian period. The marine ecosystems were teeming with life. Trilobites remained the most common animals, occupying nearly every marine niche imaginable, from bottom-dwelling scavengers to swimming plankton-eaters. Shelled cephalopods came second, ranging from the small, deciduous-shelled orthroceratoids to the enormous, planktivorous orthocones. Crawling the seabeds were more trilobites, as well as marine mollusks like snails, slugs and “chitons”, homalozoans (asymmetrical relatives of sea stars), ancient crustaceans and cheliceratans (sea spiders, sea scorpions, arachnids and horseshoe crabs). The equatorial waters boasted coral reefs much like today’s, but outside of that, the sunlight-reliant corals gave way to flower-like crinoids, oval-shaped cystoids, nut-like blastoids, moss-like bryozoans, brachiopod shellfish, tube worms similar to the giant tubes of the deep or the Christmas trees back home and tube-like tentaculoids. Freely swimming the spaces were eel-like conodonts and armor-headed jawless fish. However, prior to 445 million years ago, a particular kind of fish called Entelognathus began to open its mouth for a more efficient method of feasting.
On land, the 50 granitic landmasses had fused into 36, slowly but surely assuming the familiar shapes of today’s continents. At the time, the largest of those landmasses was Terra Australis, a large continent that would one day become Sahul and Antarctica. With few predators to eat them, plants and fungi diversified massively, carpeting the landmasses with the first forests. Not quite the exotic coal swamps of the Carboniferous, but close enough. Oddly, the pteridophytes, the group consisting of ferns and horsetails to name a few, never existed on Great Lakes Earth. In their place, the hornworts, liverworts and mosses boasted a greater diversity than back home. But the old days of the non-vascular plants were numbered, for they could not withstand competition against the lycopods and progymnosperms that quickly captured the topsoil created by millions of years of lichen accumulation. Some arthropod species did cross the boundary between sea and land, but their impact on plant evolution was surprisingly minimal.
444,400,000 years ago, biodiversity witnessed a sudden, steep drop — the signs of a mass extinction. What caused it?
As it turned out, this had been a long time coming. During the Cambrian, plants had exchanged water-logged station for vascular transportation. According to Thomas Algeo of the University of Cincinnati, this is initially bad news. Vascular plants had deep roots, which break up rocks and enrich the soil already established by the lichens. Unlike the lichens, though, the plants’ breakdown of the rocks resulted in a release of minerals and nutrients, washing them away to rivers and then to the oceans. Once there, they had become food for plankton, creating a series of algal blooms that went out of hand as they eventually deprived the oceans of oxygen, suffocating the life beneath the surface.
But plants were not the sole culprit.
In a duration varying from 750,000 to one million years, Terra Australis erupted in a series of lava flows that, in total, created a basaltic plateau covering a volume of 77 million square miles — enough to bury all of North America to the height of Denali. The lava released excess carbon dioxide into the atmosphere, raising global temperatures by 25 degrees Fahrenheit. Incidentally, this worsened the algal blooms as the extra supply of greenhouse food made them grow bigger and bigger. On land, this same thing turned the continental interiors into deserts as dry as the Atacama or the Namib today. With rain becoming increasingly rare, the relationship between fungi and algae became estranged, and the waterlogged plants were under constant threat of drying up.
But the final factor would put a stop to the algal blooms once and for all.
From space, a ball of iron 25 miles wide slammed into eastern North America, creating a crater 300 miles wide and 20 deep. This crater would be the core to the creation of Lake Agassiz. The explosion, approximately a dozen billion times more powerful than the bomb that destroyed Hiroshima, intially created global forest fires and tsunamis strong enough to drag some pieces of the algal blooms inland. The energy that escaped the explosion only to rain back to the surface as fire was the last straw for the waterlogged plants, already under duress by competition and desertification. But the vascular plants seemed pre-packaged for this — wooded stems and hard-coated seeds lessened the damage and ensured the survival of the next generation.
The impact also released a thick cloud of dust, soot and debris that shrouded the planet into darkness. (Not total, but with enough light remaining to be compared to dusk, the darkest part of twilight before nightfall.) With photosynthesis reduced to a bare margin and temperatures dropping rapidly, the algal blooms stopped expanding and instead sank to the bottom of the oceans. The dark and the cold also drew all surviving non-vascular plants into extinction.
In all, an estimate of 75% of terrestrial species and 95% of all marine species died out. This would be the only mass extinction of bacteria and fungi.
BACTERIA
Eobacteria
Sneathiellales
Kiloniellales
Kordiimonadales
Alteromonadales
Granulosicoccaceae
Thioalkalispiraceae
Hahellaceae
Litoricolaceae
Oleiphilaceae
Sinobacteraceae
Syntrophorhabdaceae
Bacteriovoracaceae
Desulfarculales
Desulfomicrobiaceae
Desulfonatronaceae
Kofleriaceae
Nannocystaceae
Phaselicystidaceae
Planctobacteria
Actinobacteria
FUNGI
Blastocladiomycota
Chytridiomycota
Microsporidia
Coniocybomycetes
Xylonomycetes
Entomophthoromycota
Kickxellomycotina
Mucoromycotina
Zoopagomycotina
The combination of heat, drought, fire, cold and dark put a damper on plant diversity as well.
NEMATOPHYTA
CHLOROPHYTA
Pyramimonadophyceae
Mamiellophyceae
Chlorodendrophyceae
BRYOPHYTA
MARCHANTIOPHYTA
ANTHOCEROTOPHYTA
HORNEOPHYTOPSIDA
RHYNIOPHYTA
ZOSTEROPHYLLOPSIDA
TRIMEROPHYTOPSIDA
LYCOPODIOPHYTA
And of course, there are the multitudes of animals who back home would have been mascots of the Paleozoic but short-lived on Great Lakes Earth.
LOBOPODIA
PORIFERA
Pharetronida
Amphidiscosida
Aulocalycoida
Hexactinosa
Lychniscosa
Demospongiae
ANNELIDA
Aeolosomatidae
Cossunidae
Maldanidae
Paraonidae
Parergodrilidae
Potamodrilidae
Psammodrilidae
Questidae
Scalibregmatidae
Amphinomida
Eunicida
Aphroditidae
Eulepethidae
Pholoidae
Goniadidae
Lacydoniidae
Paralacydoniidae
Spirorbidae
Apistobranchidae
Longosomatidae
Magelonidae
Poecilochaetidae
Trochochaetidae
Uncispionidae
Ctenodrilidae
Fauveliopsidae
Flabelligeridae
Flotidae
Poeobiidae
Sternaspidae
Trichobranchidae
Lumbriculida
Moniligastrida
Machaeridia
GNATHOSTOMULIDA
HEMICHORDATA
PHORONIDA
CTENOPHORA
CNIDARIA
Anthozoa
Myxozoa
BRACHIOPODA
HYOLITHA
ENTOPROCTA
ARTHROPODA
Trilobitomorpha
Pycnogonida
Merostomata
Thylacocephala
Cephalocarida
Pentastomida
Mystacocarida
Tantulocarida
Syncarida
Peracarida
Phyllocarida
Marrellomorpha
DINOCARIDIDA
MOLLUSCA
Oncocerida
Tarphycerida
Discosorida
Endocerida
Actinocerida
Orthroceratoidea
Bactritida
Helcionelloida
Monoplacophora
Aplacophora
Gastropoda
ECHINODERMATA
Homalozoa
Crinozoa
Blastozoa
Ophiocistoidea
CONODONTA
OSTRACODERMI
Sources vary on how long it took Great Lakes Earth to recover from its first — and worst — mass extinction. Some say it took 12 million years. Others say 16. Was the loss of life that extensive? Did it take that long for the surviving plants and lichens to absorb the excess carbon dioxide from the atmosphere? Or did the die-off of bacteria and fungi delay the recovery process?
Whatever the reason, the sponges, worms, nautiloids and echinoderms suffered a substantial loss and took the longest time to return to their former diversity. For the survivors who had been ecologically rare before the extinction event — decapods, branchiopods, barnacles, ostracods, arachnids, stars, urchins, chitons, octopus, squid, cuttlefish, bivalves and jawed fish — excess opportunity was around every corner. They would radiate into forms far more diverse than they ever were or are back home.
Invasion of the Land
400 million years ago, there were now five landmasses on Great Lakes Earth. The atmosphere had 2500 parts of carbon dioxide per million, and the average global temperature was 70 degrees Fahrenheit. As a result, rainforests and swamps were the two predominant habitats on all five landmasses. Basal conifers towered high above the soil, bearing resemblance to hemlocks, yews, sequoias or even baobabs. Tangled-up rhizophyte trees resembled hundred-foot-tall mangroves with canopies resembling upside-down umbrellas of large, broad fronds. Ichthyophyte trees, so named after their bark resembling fish scales, had long, thick roots anchoring puny structures resembling the monkey puzzle trees back home on diet pills. But perhaps the most common of those trees were the ginkgoes, broad-leaved descendants of a family of trees who became extinct shortly after the End-Paibian extinction event. On the early trees’ feet were dense carpets of mushrooms, glomeromycetes and gnetophytes of a diversity far greater than the shrub-like and flower-like three genera and 70 species back home. Some of those would have resembled the ferns and horsetails back home. Between both extremes would have been a dense understory of cycadophytes, plainer-looking and more basal than the familiar cycad image. Worms, insects, arachnids, centipedes, millipedes and crustaceans ran rampant in such forests and swamps.
Beneath the surface, life in the oceans soldiered on. Crustaceans, jellyfish and hydrae became the new planktonic mass. In the absence of the snails and slugs came Platyhelminthes, the roundworms. The sponges who survived would have found themselves surrounded by the first worm forests — tall, extravagant, photosynthetic worms in dense quantities lording over equally dense carpets of barnacles, clams, mussels and oysters. The concave-shelled, homomorphic (regularly coiled) nautiloids diversified until one group became the convex-shelled, heteromorphic (irregularly coiled) ammonoids. Chitons and urchins crawled on the ocean floor, under constant attack from the crabs, lobsters and mantid-shrimps. The ancestral jawless fish were now exclusive to the roles of scavengers and parasites. But from the jawed underdog Entelognathus came Placodermi (armored fish), Acanthodii (spiny fish), Chondrichthyes (cartilaginous fish) and Osteichthyes (bony fish), occupying three-quarters of the global capacity of 40,000 species.
400 million years ago came an ambitious little fish called Tiktaalik. Its lobed fins were so advanced that they allowed the animal to crawl from the water to land. Today, scientists believe this species was the midway between the completely water-bound fish and the more terrestrial amphibians.
342 million years ago, a small group of amphibians had found it advantageous to lay their eggs on land, not in the water. This creative thinking gave way to the Great Amniote Branch, a biological phenomenon in which one common ancestor branched out into two major groups — Reptilia and Synapsida. Both sides had a great destiny ahead, one being reptiles and then dinosaurs, the other being the seeds of the mammal family tree. Both went away from the fully sprawled legs of their amphibian ancestors and improved their postures into semi-erect. Both sides had evolved four-chambered hearts from the three chambers of their ancestors’ hearts. Both had 15% of their overall body volume accounted for by their respiratory systems. But that is the end of the similarities. One side retained the regulation of their amphibian ancestors and gained their energy from the sun, the other evolved a process to better control their body temperatures. One side evolved air sacs that resulted in a unidirectional respiratory system (oxygen gets in and out), the other just a larger heart and pair of lungs (oxygen gets in, carbon dioxide gets out). One side would have two skull openings behind each eye, the other only one. One side would have teeth of uniform shape and size, the other more diverse, more specialized teeth to suit specific purposes.
For the next 150 million years, Great Lakes Earth would enjoy a stable greenhouse climate. Forests and swamps dominated the continents. In the time of Tiktaalik, the atmospheric volume of oxygen was 140% higher than today, high enough for the existence of truly monstrous arthropods. A swamp in western Russia had centipedes as long as pythons. One British island had a spider as heavy as a basketball. Sawflies as large as finches hovered above a Canadian rainforest.
But the B-movie bugs didn’t have these swamps and forests to themselves, of course. Amphibians boasted the greatest terrestrial vertebrate diversity, occupying niches that would later be occupied by lizards, crocodilians, snakes and small mammals. The earliest reptiles, like Hylonomus and Petrolacosaurus, would have been small, basal and lizard-like. They may have evolved the semi-erect stance, the four-chambered heart and the air sacs that created a unidirectional respiratory system (which in all reptiles, past and present, made up 15% of their total body volume) for faster, longer-lasting speed either after prey or away from predators. Lording them all were large, specialized synapsids, from the herbivorous Edaphosaurus to the infamous fisherman Dimetrodon. It may be this varying degree of specialization that prohibited the synapsids from having unidirectional air sacs like the reptiles. They and their descendants, the mammals, also have 15% of their body volume devoted to respiration, but unlike the reptiles, all of that volume is devoted to the lungs themselves. They could not bother to pursue their prey over long distances, so certain species specialized on only one type of food. Some ate leaves, others gave seeds a try. Some, like Dimetrodon, fished for fish, while others pried the muddy waters for insects or crustaceans or mollusks.
150 million years of such ecosystems had a lasting legacy today — when the plants died, they decomposed into the soil. Millions of years of pressure and heat turned their rotting remains into a black rock — coal. 150 million years of global coal-bearing forests created so much coal that by the time the Industrial Revolution began, there would have been more than one quadrillion tons of coal worldwide.
While the coal swamps dominated the land, fish dominated the oceans. Bony fish made up the minority, consisting solely of those in exclusive reef niches. The spiny fish swam in schools, occupying niches that back home belong to both forage fish (herrings, sardines, anchovies, silversides, etc.) and oily fish (carps, salmon, tuna, mackerel, etc.). Some of the armored fish were oceanic filter feeders (like basking or megamouth sharks) and some others, like the notorious Dunkleosteus, were coastal apex predators. There was a greater diversity of cartilaginous fish than ever before or since.
All that remarkable diversity changed 250 million years ago, when too little carbon dioxide remaining in the atmosphere cooled the planet down and all the continents had joined together once again, becoming the enormous landmass Pangaea.
Pangaea
With so much carbon dioxide being absorbed by the swamps, not enough of it returned to the atmosphere, cooling the climate. The cause of the Carboniferous-Permian Big Freeze, as it came to be called, then, was that the climate was too cold for some, too dry for others or both.
In all, the death toll from the Big Freeze was 80%. Casualty list:
PROGYMNOSPERMOPSIDA
RHIZOPHYTA
ICHTHYOPHYTA
PINOPHYTA
Voltziales
Cordaitales
Vojnovskyales
GINKGOPHYTA
Umaltolepidiaceae
Yimaiaceae
Schmeissneriaceae
ECHIURA
ARTHROPODA
Palaeodictyopteroidea
Glosselytrodea
Miomoptera
Protorthoptera
Caloneurodea
Plecoptera
Hagloidea
Schizodactyloidea
Tanaoceroidea
Trigonopterygoidea
Blattoptera
Monura
Meganisoptera
Eurypterina
Arthropleuridea
Diplostraca
Uraraneida
Trigonotarbida
Haptopoda
Phalangiotarbi
Carbonitidae
MOLLUSCA
Cardiida
Agoniatida
Clymeniida
Goniatitida
PLACODERMI
ACANTHODII
CHONDRICTHYES
Cladoselachiformes
Symmoriida
Eugeneodontida
Janassidae
Pristodontidae
Belantesidae
Sibyrhinchidae
AMPHIBIA
Leposondyli
Limnarchia
Anthracosauria
Edopoidea
REPTILIA
Araeoscelidia
SYNAPSIDA
Caesarsauria
Varanopidae
Ophiacodontidae
Edaphosauridae
250 million years ago, whole divisions and classes of plants became extinct. The ginkgoes had lost 60% of their original diversity and never bounced back. The conifers had lost 75% of their original diversity, but in time, they did recover. The cycads and gnetophytes didn’t seem to have suffered any losses at all.
As the climate grew cooler and drier, the amphibians which originally owned 90% of all terrestrial vertebrate niches had lost 68% of that original diversity. Half of the reptiles and 85% of the synapsids also became extinct, but for the survivors, the thinning of the amphibians provided room to expand. The sole survivors of the pelycosaur lineage, the sphenacodonts, evolved into the next line of mammal evolution — they had become the therapsids, the first direct ancestors of the mammals. The reptiles, in turn, evolved into an equally high variety of shapes, from the earliest of the testudinatans and the lizard-like rhynchocephalians to the silesaurs, the direct ancestors of both crocodylomorphs and dinosaurs.
The spiny and armored fish used to be the most successful of Great Lakes Earth’s fish, but only because the warm, wet climate ensured their success through specialization. The Permian Big Chill was just too cold or too dry or too both for their own good. This gave rise to the modern shark, larger and more predatory than ever before. In turn, this was a godsend for the bony fish, and they, too, diversified like never before. This sort of diversification barred out of existence on Great Lakes Earth the two major groups of marine reptiles — the flippered Sauropterygia, the group that cryptozoologists believe included the notorious Loch Ness Monster, and the fish-like Icththyopterygia.
The Pangaea that dominated Great Lakes Earth from 250 to 200 million years ago is arranged slightly differently from ours.
250 million years ago, the reduction in atmospheric carbon dioxide was so great that the mean surface temperature dropped from 63 degrees Fahrenheit to 55 degrees. This may sound trivial, but 150 million years of stability made the plants and animals specialized and therefore overly sensitive to temperature change. From 250 to 200 million years ago, all of what we’d call Russia would be a collective chain of plateaus. One other plateau would have covered South America’s southern half, southern Africa and West Antarctica, which means the ice extended no further than Sahul or East Antarctica. In Pangaea’s northern half, forests and swamps still dominated the lowland areas.
In such dense lowlands, reptiles were common, from agile Silesaurus to aerial Icarosaurus, who flew via ribs elongated into wings; whereas therapsids were rare, from the mongoose-like therocephalians to the dog-like cynodonts. In the more open uplands, by contrast, reptiles were rare yet these habitats were where the therapsids were at their most common, from rhinoceros-sized-hippopotamus-like Lystrosaurus to grizzly-bear-sized-pit-bull-like Inostrancevia. These creatures would have taken advantage of their oversized hearts and lungs by squeezing every sparse ounce of oxygen from the thin mountain air into their noses and mouths. Still, because they exhaled carbon dioxide, their method of breathing was still inferior to the unidirectional air sacs that the reptiles retained. However, compensation came in the form of legs tucked straight underneath the body, like pillars tucked beneath a roof or ceiling.
The weirdest of Pangaea’s reptiles would be the arboreal varieties, from gliding weigeltisaurids and kuehneosaurids to the long-necked protorosaurs. Oddly, the armored aetosaurs, the crocodile-like phytosaurs and the formdiable but awkwardly-bipedal rausuchids never existed on Great Lakes Earth, their niches filled instead by crocodylomorphs and therapsids.
In the rainforests of northern Pangaea, a small, omnivorous silesaur became Eoraptor and Eodromaeus, the first dinosaurs, 230 million years ago, as was the case back home. A species of cynodont branched out into the first mammals, which came out at the same time. Both groups started out small and insignificant, unable to compete with the larger predators like Gorgonops. Back home, it would have taken at least ten million years for the likes of the three-foot-long-22-pound Eoraptor and four-foot-long-11-pound Eodromaeus to grow into the 30-foot-long-four-ton Plateosaurus and the 17-foot-long-300-pound Liliensternus. On Great Lakes Earth, however, such growth would have to wait until some global catastrophe opened many fields available for them. So until the Die-Odd, all of the world’s dinosaurs were just oodles of Eoraptors, Pisanosaurus and Panphagias.
Rise of an Empire
200 million years ago, the continents began to rip apart and leave the south pole, melting the ice caps and warming the climate. North divorced south. A piece of east Africa split from the mainland, becoming India. Pangaea now became two continents — Laurasia (North America, Asia, Europe and Greenland) and Gondwana (South America, Africa, Sahul and Antarctica).
70% of all life died out, not because of some catastrophic smoking gun, but simply because the plants and animals had become too cozy with the Permian’s cold, dry climate. Casualty list:
MOLLUSCA
Prolecantida
Ceratitida
Tainocerataceae
Clydonautilaceae
Trigonocerataceae
OSTEICHTHYES
Pholidopleuriformes
Scanilepiformes
Palaeonisciformes
Dapediiformes
Leptolepiformes
Ginglymodi
Saurichthyiformes
Semionotiformes
AMPHIBIA
Seymouriamorpha
Temnospondyli
REPTILIA
Protorosauria
Poposauroidea
Parareptilia
Thalattosauria
Kuehneosauridae
Weigeltisauridae
Rhynchosauria
Captorhinidae
Silesauridae
THERAPSIDA
Therocephalia
Biarmosuchia
Eucynodontia
Dinocephalia
Anamodontia
Gorgonopsia
As Pangaea split into smaller landmasses, rainfall rose and the forests spread again. Conifers and cycads exploded in diversity, while the ginkgoes stayed right where they were. The conifers, standing 200 feet at the tallest and 40 at the widest, were the more dominant of the trees, armed either with jagged, needle-like leaves or distasteful sap or especially both. Meanwhile, the oak-like and maple-like ginkgoes stood 50 feet tall and grew fruit-like structures that would have reeked of rotten meat, tempting to only a select few species. Cycads blanketed the understory. Beneath them were dense carpets of fungi, gnetums and ephedras.
From dimunitive side characters like Eoraptor, Eodromaeus, Tawa, Protoavis, Panphagia and Mussaurus came an explosion of dinosaurs, turning the planet into a dinosaur empire. They had almost immediately exploded into a myriad of shapes, sizes, colors and niches.
The return of the global forest fed a growing diversity of not just dinosaurs, but other animals as well. In the swamps, only a handful of amphibian species survived the warming trend and branched out into three distinctive orders — Anura (frogs and toads), Urodela (salamanders and newts) and Gymnophiona (caecilians). Alongside them were the earliest of Squamata (lizards) and Eusuchia (“true crocodiles”). There are even crocodylomorphs who took to the seas. Though Testudinata had been around for 40 million years by that time, the Jurassic saw the start of Testudines, the order of modern turtles. At the same time came Hymenoptera, the order consisting of wasps, bees and ants (though the latter two wouldn’t arrive until AFTER the End-Cretaceous event).
We don’t know why the iconic flying reptiles, the pterosaurs, never existed on Great Lakes Earth, but that did give the arboreal dinosaurs more room to spread their wings and diversify. This included eagle-sized Dogsuli and falcon-like Peregrinosaurus.
The first dinosaurs came out 230 million years ago, but instead of immediate diversification as was the case back home, they had to wait until the Die-Odd 200 million years ago before growing into the first giants. As a result, Great Lakes Earth during the Late Jurassic period 150 million years ago would not have seen the likes of Stegosaurus, Brachiosaurus, Diplodocus or Allosaurus.
The Cretaceous Thermal Maximum
150 million years ago, the mean surface temperature was 62 degrees Fahrenheit. 144 million years ago, that temperature rose by nine to 15 degrees. That was due to a period of massive carbon injection whose duration varied depending on whose literature you’re reading — some say over a course of 2000 years, while others say 20,000. What caused this injection? No one can say. What we can say, though, is that the result is a global climatic uniformity — from pole to pole, there could be only one category of the Köppen climate classification process, Af, tropical rainforest.
The continents of Laurasia and Gondwana began to fragment further. A long, narrow channel separated South America from the rest of Gondwana. Greenland drifted into an island, separating eastern North America from Europe.
This sudden rise in temperature resulted in a catastrophic rise in sea levels. How much of a rise in sea level happened? In comparison, the Jurassic sea levels were 120 meters (almost 400 feet) higher than today.
In the Cretaceous, western North America could have resembled the Philippine islands on a macrocosm. Eastern North America could have been fragmented by a seaway resembling a backward lower-case y. South America had split off from Africa and Antarctica, and the seaway in its northern half could have resembled a cursive S. North Africa was once a huge sea guarding an island chain similar to the Bahamas on a macrocosm. This would have been the only period in which Beringia was underwater, isolating North America from Asia. All of Eurasia might have resembled the entire Caribbean map on a macrocosm. Terra Australis (Sahul and Antarctica) might have been fragmented by a seaway resembling a cursive G.
Half of all terrestrial species and three-quarters of all marine species became extinct. Casualty list:
GINKGOPHYTA
GNETOPHYTA
RETARIA
Fusulinida
Involutinida
Acantharea
Sticholononchea
OSTEICHTHYES
Pachycormiformes
Aspidorhynchiformes
Pycnodontiformes
Amiiformes
Leptolepiformes
Macrosemiiformes
Lycopteriformes
Ichthyodectiformes
Chondrosteoidei
Errolichthyidae
Peipiaosteidae
ARCHOSAURIA
Sauropodamorpha
Coelophysoidea
Heterodontisauridae
Fabrosauridae
Scelidosauridae
Saltriosauridae
Dilophosauridae
Scansoriopterygidae
Protoaviformes
Archaeopterygidae
Thalattosuchia
Hsisosuchidae
THERAPSIDA
Dryolestoidea
Morganucodonta
Allotheria
Docodonta
Eutriconodonta
Shuotheriidae
Gobiconodonta
Amphilestidae
Tritylodontidae
Even though this sudden global warming period resulted in a loss of life, the warming itself meant that biodiversity would reach its peak. The die-off of gnetophytes and ginkgophytes also resulted in the evolution of a new kind of plant — the angiosperms, or flowering plants.
At the time of the Cretaceous Thermal Maximum, the dinosaurs underwent two major splits — ancestral and avian. At the same time, Squamata underwent its own split — the ancestral lizards now had to deal with their slippery upstarts, the snakes.
Because dinosaur diversification came late compared to back home, as well as the dense, confined rainforest habitats, the Cretaceous would have been subject to…
In this hot, humid climate, plants, fish, amphibians, reptiles, mammals and birds would have spread and diversified as though nature had gone madder than a hatter. No pterosaurs means a whole lot of birds, probably second to today’s diversity. There were crocodylomorphs occupying plenty of niches, from apex river predators like today to terrestrial hunters like Kaprosuchus, the “Boar Croc”, and even plant-eaters like duck-billed Anatosuchus. The most common of lizards would have been small, arboreal species resembling geckoes, dracos and iguanas. There was a whole slew of turtles, too, from marine filter-feeders to pond predators. The dinosaurs would not have been familiar to us — one-ton raptors against nodosaurs protected by sword-like osteoderms made of carapace; four-legged dryosaurs with 65% of their six-to-thirteen-yard lengths being broad, stiff tails; wolf-sized compsognathids that could bring down larger prey by hunting in temporary packs; ornitholestids with extreme cases of sexual dimorphism than just having a horn on the male’s nose; and caudipterids measuring eight yards in length, two-and-a-half tons in weight and originating from eggs two feet long.
The CTM resulted in the extinction of mammals that back home endured throughout the Cretaceous and even into the Neogene. This would result in the early diversification of modern mammals, right? Not exactly. The basal ancestors of modern mammals DID evolve in the Cretaceous, but they had to stay in the literal and ecological shadows of not just the dinosaurs and the reptiles but also their fellow mammals — the opossum-like cimolestans and the bipedal leptictidians, not to mention the opossums, possums, numbats, bandicoots, bilbies, quolls, stagodonts and deltatheroids that combined to belong to the pouch-bearing metatheres. And, of course, there were the most ancient of all true mammals, the egg-laying monotremes, who, at the time, were the most common mammals of Gondwana.
80 million years ago, the bird and mammal world had been overrun by cosmopolitan or near-cosmopolitan species. Gondwana would have been overrun with the tenrec-like Afrotherium. North America, Asia and Europe shared the title of having the most numerous species of one mammal genus — shrew-like Laurasiatherium. Mouse-like Glires, hoofed Hyopsodus and weasel-like Miacis came a very close second.
Gondwana would have been full of cosmopolitan numbers of species of one genus of birds that would prove to be the ancestors of…
Once the End-Cretaceous event would clean the slate, subsequent orders of birds would expand from some of those listed above.
Laurasia also had its share of near-comsopolitan genera who would descend into…
The only genus to be truly cosmopolitan during the Cretaceous was Aequornis, and when it survived the End-Cretaceous event, it would radiate into the following orders —
You might think that such a list would mean that these birds would be around during the Cretaceous. In truth, the more familiar shapes would not be apparent until AFTER the End-Cretaceous event. Until then, they could not hope to compete against the numerous but homeothermic and parentally-careless enantiornithines. Nonetheless, their near-global distribution reinforce the fact that these were not fussy eaters, nor did they have a preference as to which terrain to call home. This unbiased environmental preference would help these small, unassuming-looking birds and mammals survive the really hard times ahead.
The End of the Empire
The Great Tectonic Excess, lasting from 80 to 30 million years ago, is a period where major mountain ranges were being formed almost at once. In the case of the final days of the Cretaceous, it was the Rocky Mountains of North America, the Andes of South America and the Himalayas of Asia. At the same time, the seafloor began to slow down, withdrawing inland seas from the continents and creating new bridges for plants and animals to cross. This also resulted in more continental climates — warmer summers, cooler winters, hotter days and colder nights. At the same time, a combination of fault-blocking and uplifted passive margins enlarged the islands of North Africa until the area of land was larger than the area of seawater. Also, a piece of Europe split off from the mainland. This piece would one day become the British Isles.
65 million years ago, western North America suffered an extensive scar. Wedged between the young Rocky Mountains to the east and the Pacific Ocean to the west, a’a lava (basaltic lava with fragmented, rough, blocky or even jagged surfaces) bled out from the West, creating an igneous province covering an area of one and a half million square miles and a total volume of one million cubic miles. The lava had been flowing for a duration of ten to 12,000 years, more than fast enough to create a mass extinction. When they cooled, actually, they would mark the initial foundations of the creation of the Great Lakes of the West.
But for the moment, life on Great Lakes Earth had to deal with 12,000 years of brutal overheating. The first die-off was moderate among the terrestrial species as the lava belched out dense clouds of carbon dioxide into the atmosphere.
But then the warming came to a point where, as was the case at the end of Great Lakes Earth’s first ever ice age, the entire global supply of methane hydrates melted and entered the atmosphere as methane gas, heating up an already warm planet by 15 degrees Fahrenheit. Desertification ran rampant. Each continent was subject to its own dust bowl, leaving the coastal margins the only real estate available.
Ocean circulation shut down completely, turning the great waters as hot and as still as a bath. Shallow seas near continental shelves would do fine, but epicontinental, or inland, seas evaporated into vast salt flats, destroying entire marine ecosystems.
The biotic damage was simply beyond comprehension. 100% of the cyadophytes and three-quarters of the conifers did not make it.
Sciadopityaceae
Cupressaceae
Cunninghamhiaceae
Taiwaniaceae
Arthrotaxidaceae
Taxodiaceae
Callitraceae
Araucariaceae
Podocarpaceae
Such losses provided much more than enough space for the then-ecologically-rare angiosperms, the flowering plants, to branch out and diversify. That said, not all of them survived the End-Cretaceous event.
Magnoliales
Laurales
Saxifragales
Fagales
Moraceae
Cestraceae
Goetzeaceae
Petuniaceae
Schizanthaceae
Schwenckiaceae
Salicaceae
Cannabaceae
The entire invertebrate system had been cut down by half.
ONYCHOPHORA
MOLLUSCA
Rostroconchia
Nautiloidea
Ammonoidea
Belemnoidea
Vampyromorphida
Antillocaprinidae
Caprotinidae
Dictyoptychidae
Ichthyosarcolitidae
Plagioptychidae
Polyconitidae
Radiolitidae
ARTHROPODA
Hoplocarida
Notoptera
Protocoleoptera
Myxophaga
Glypheidea
Mesothelae
Archostemata
Symphyta
Coleorrhyncha
Mecoptera
Archaeognatha
Apterygota
Dermaptera
Embioptera
Megaloptera
Notoptera
Plecoptera
Raphidioptera
Siphonaptera
Strepsiptera
Thysanoptera
Trichoptera
Zoraptera
Amblypygi
Opiliones
Palpigradi
Pseudoscorpiones
Ricinulei
Schizomida
Thelyphonida
Mymarommatoidea
Anaxyeloidea
Nevrorthidae
Myrmeciidae
Seven species of cartilaginous fish out of eleven could no longer boast about their evolutionary immortality.
Holocephali
Hexanchiformes
Xenacanthida
Acrodontidae
Lonchidiidae
Polyacrodontidae
None of the jawless Agnatha survived the End-Cretaceous extinction event.
Seven species of bony fish out of 20 dessicated into extinction.
SARCOPTERYGII
Actinistia
Ceratodontiformes
ACTINOPTERYGII
Chondrostei
Cladistia
Holostei
97% of all the amphibians were gone.
Allocaudata
Cryptobranchoidea
Archaeobatrachia
Mesobatrachia
Apoda
Sirenidae
One-third of Squamata, the lizards and the snakes, died out.
Carphodactylidae
Diplodactylidae
Cordylidae
Gerrhosauridae
Agamidae
Amphiboluridae
Hydrosauridae
Leiolepididae
Uromasticidae
Paleophiidae
Nigerophiidae
Madtsoiidae
Boidae
Half of the turtles did not make it.
Chelydridae
Carettochelyidae
Protostegidae
Adocidae
Baenidae
Of all the extant reptile supergroups, Crocodylomorpha was hit the hardest — four species out of five had vanished, leaving the only survivors being Alligatoridae and Crocodylidae.
Notosuchia
Trematochampsidae
Peirosauridae
Tethysuchia
Goniopholididae
Paralligatoridae
Sebecosuchia
Some groups of reptiles were completely wiped out as a result of the End-Cretaceous event, like the rhynchocephalians (tuataras) and the choristoderans (“false crocodiles”).
The Great Dying wiped out 70% of all the dinosaurs…
Ornithischia
Enantiornithes
Hesperornithes
Alvarezsauria
Compsognathidae
Caudipteridae
Dromaeosauridae
Ornitholestidae
Noasauridae
…and 85% of the mammals.
Metatheria
Leptictidia
Cimolesta
Afredentata
Steropodontidae
Obdurodontidae
Megalibgwilidae
In all, 60% of terrestrial species and 85% of marine species became extinct.
The odd thing is that some of those casualties we can still find back home, so how come they became extinct on Great Lakes Earth 65 million years ago whereas they are still alive back home? During the Cretaceous, there was no environmental diversity — the only terrestrial habitat were tropical rainforests. This bred the ultimate diversity, but at the cost of overspecialization. When the lava erupted and created the mess 65 million years ago, most of the plants and animals did not have the flexibility to withstand the sudden environmental stress and became extinct.
Even so, evolution still managed to rise from the ashes and soldier on.
The Icing of Antarctica
It took Great Lakes Earth three to five million years to recover from the End-Cretaceous event. When it did, the climate was so much cooler and drier than the Cretaceous that the tropical rainforests could reach no further than latitudes 55 degrees. Which means hot, steamy forests as far north as Hadrian’s Wall. Outside of that zone, the climate would be classified by Wladimir Köppen as “Csa” — hot-summer Mediterranean.
The global jungles used to harbor conifers and cycads, the floral ecological minority consisting of their angiosperm upstarts. After the Great Dying, the lowland jungles were exclusively angiosperms. The conifers that survived the Great Dying sought refuge in the cooler, drier, rockier highlands.
The Great Tectonic Excess continued on. The Arctic Plate began to sink beneath the Northern Plate, creating a series of volcanic mountains lining the coasts of Scandinavia, Russia, Alaska, Yukon and the Northwest Territories. The Indian and Atlantic oceans sank beneath Africa, creating the Aden Bahçesi mountain ranges. Terra Australis began to split from Africa. And the seafloor just kept on receding. And then there were the eruptions of the Siberian Traps, lasting from 60 to 43 million years ago, covering an area of 11 million square miles and a total volume of four million cubic miles.
Although the Siberian eruptions started 60 million years ago and ended 43 million years ago, they were at their most vigorous from 51 to 45 million years ago, when at least 75% of the basalt were released. Though extensive, the eruptions happened too slowly for them to cause another mass extinction (albeit one so soon after the Cretaceous). What DID happen, however, is that they made Asia a no-cross zone, fragmenting the mammal populations into distinct groups. It wouldn’t be until 36 million years ago that Asia would be reopened to migrators.
From 60 to 45 million years ago, the descendants of Afrotherium and Afroavis dominated Africa. Primitive owls hunted the treetops for trogons and mousebirds. The swamps were filled with tapir-like proboscideans, from Moeritherium to Palaeomastodon. 60 million years ago, the rivers and lakes of Africa would have been the territories of creatures like semi-aquatic Pakicetus and the more amphibious Ambulocetus. 15 million years later, their descendants were lords of the Tethys. With no primates and few bird and reptile predators, each African tree had its own population of sloths and tamanduas, whereas the pangolins, the armored anteaters, scrounged the dangerous forest floor for insects. In the absence of rodents, shrews and true moles, there would be instead armadillos, golden moles, tenrecs, hyraxes and sengis.
During the Jurassic and Cretaceous, the monotremes were the most common mammals of Gondwana. Since the End-Cretaceous event, though, Sahul became their final stronghold. With the pouch-bearing metatheres wiped out entirely, they had room to expand, experiencing a radiation that they had never witnessed before.
South America was, believe it or not, a more isolated place to be. It was here that you’d find herds of meridiungulates, from elephant-like pyrotheres to rhino-like notoungulates, being shadowed in every corner by caimen, monitor lizards and carnivorous creodonts.
The European species of Laurasiatherium branched out into megabats, shrews and hedgehogs. The European species of Miacis branched out into Feliformia. The European species of Hyopsodus branched out into the even-toed ungulates. The European species of Glires proved to be the ancestors of all primates.
The North American species of Laurasiatherium branched out into microbats and moles. The North American species of Miacis branched out into Caniformia — dogs, bears, raccoons, pandas, bear-dogs, skunks, weasels and dog-bears. The North American species of Hyopsodus branched out into the odd-toed ungulates — horses, rhinoceros, tapirs, chalicotheres and the brontotheres, recognizable through the horn-like appendages on their skulls. The North American species of Glires proved to be the ancestors of all rodents.
Sub-Himalayan Asia became the last stronghold of the rhino-like dinoceratans and the hoofed meat-eaters, the mesonychids, provided that they were more common in Asia before the eruption of Siberia.
The real final straw came 45 million years ago, when Sahul decided to split from Antarctica, leaving the southernmost continent on Great Lakes Earth all alone. After millions of years of major detours with mild results at most, the Antarctic Circumpolar Current finally encircled Antarctica, freezing the entire landmass into the world’s largest icebox. But even geologically speaking, this was not an overnight success. Coverage by snow and ice by 100% wouldn’t be reached until five million years ago.
Much of a delay as it may be, the initial icing of Antarctica DID influence the world. The climate began to slope into cooler and drier weather, shrinking the global rainforests. Outside the rainforests, temperate forests would give way to savanna, and savanna would give way to either grasslands or deserts.
The Icing of Antarctica seemed to have no effect on the diversities of invertebrates, fish, amphibians or reptiles. But if one were to combine bird and mammal diversities together, we’d find that the Icing of Antarctica eliminated one species out of four.
AVES
Aegialornithidae
Limnofregatidae
Palaeeudyptidae
Paraptenodytidae
Ameghinornithidae
Idiornithidae
Salmilidae
Psilopteridae
Ogygoptyngidae
Palaeoglaucidae
Protostrigidae
Sophiornithidae
Eremopezidae
Fluvioviridavidae
Gastornithidae
Presbyornithidae
Eocoraciidae
Messelornithidae
Messelirrisoridae
Primobucconidae
Quercypsittidae
Vastanavidae
MAMMALIA
Dinocerata
Mesonychia
Archaeoceti
Plesielephantiformes
Brontotheroidea
Anoplotherioidea
Anthracobunidae
Palaeotheriidae
Cainotheriidae
Oromerycidae
Dichobunidae
The African Connection
40 million years ago, Balk collided with southeastern Europe, creating the Alps. At that time, the afrotheres and Gondwana-birds that tagged along Balk as it broke off from mainland Africa and journeyed to Europe got off the island, now reestablished to be a peninsula, and colonized mainland Eurasia.
32 million years ago, Africa’s status as an island continent was under threat, as a tectonic snag barred the connection between the Tethys and the Atlantic, creating a landbridge that extended from the Portuguese and Spanish coastlines to the Moroccan and Algerian coastlines.
In the long sight, this was an opportunity for Europe’s animals. Four million years earlier, in the aftermath of the last of the Siberian eruptions, migrants colonized Asia from both Europe and North America. But the landbridge opened a new road for the migrators to cross.
For six and a half million years, all of Africa, Europe, Asia and North America were loaded with rodents, bats, afrotheres, ungulates, feliforms, caniforms, primates, ducks, geese, swans, parrots, owls, seriemas, mousebirds, trogons, woodpeckers, honeyguides, songbirds (the Icing of Antarctica coincided with new orders of birds radiating from Passeriformes and Tyranniformes), shorebirds, gamebirds and raptors.
But the connection was permanently cut off 25.5 million years ago, as the Atlantic Ocean finally breached the Gibraltarian dam that created the landbridge in the first place. But by then, the damage was already done. The birds and mammals that were exclusive to at least one continent now had a far wider distribution. After 25 million years ago, the ecological makeup started to look more like this:
AFRICA
Springhares, mole rats, cane rats, true mice, gerbils, jerboas and climbing mice (Rodentia)
Deinotheres, stegodonts, tenrecs, sengis, glyptodonts, tree sloths, tamanduas and pangolins (Afrotheria)
Once-basal three-toed horses, running rhinoceros, hornless rhinoceros and swimming rhinoceros (Perissodactyla)
Peccaries, mouse deer and hard-hooved camels (Artiodactyla)
Mongeese and civets (Feliformia)
Dog-bears, agriotheres and short-faced bears (Caniformia)
Lemurs, galagos, lorises, tarsiers, colobids, baboons, swamp monkeys, talapoins, vervet monkeys, guenons and apes (Primates)
Whistling ducks, white-backed ducks, freckled ducks, spur-winged geese, shelducks, sheldgeese and stiff-tailed ducks (Anseriformes)
“Terror birds” and secretary birds (Cariamiformes)
Barbets and honeyguides (Piciformes)
Guineafowl, currasows and megapodes (Galliformes)
Bitterns, tiger herons, night herons, ibises and spoonbills (Pelicaniformes)
Crowned cranes, trumpeters, sungrebes and flufftails (Gruiformes)
Forest falcons, snake eagles, large kites and honey buzzards (Falconiformes)
Ostriches and elephant birds (Palaeognathae)
NORTHERN HEMISPHERE
Hystricomorphs, gophers, dormice, voles, lemmings, squirrels, chipmunks, flying squirrels, marmots and rats (Rodentia)
Elephants, shovel tuskers, gomphotheres, mastodons, giant anteaters and ground sloths (Afrotheria)
One-toed horses (Perissodactyla)
Pigs, entelodonts, antelopes, soft-hooved camels, musk deer, telemetacarpal deer, plesiometacarpal deer, sheep, goats and cattle (Artiodactyla)
Saber-toothed cats (Feliformia)
Bear-dogs, bears, dogs, skunks, badgers, weasels, wolverines, martens, ferrets, polecats, raccoons, coatimundis, kinkajous, olingos, olinguitos, ringtails and cacomistles (Caniformia)
Macaques, geladas, mangabeys, drills and mandrills (Primates)
Geese, swans, dabbling ducks, diving ducks, sea-ducks and perching ducks (Anseriformes)
Seriemas (Cariamiformes)
Puffbirds, jacamars and woodpeckers (Piciformes)
Pheasants, peafowls, partridges, grice and quails (Galliformes)
Herons and bitterns (Pelicaniformes)
True cranes, rails and limpkins (Gruiformes)
Falcons, caracaras, eagles, hawks, harriers and small kites (Falconiformes)
Rheas and tinamous (Palaeognathae)
There were birds and mammals that you’d find in both super-regions — owls (Strigiformes), sea herbivores (Desmostylia), hyenas, purring cats, roaring cats (Feliformia), otters, pandas (Caniformia) and hyraxes (Afrotheria).
This may seem like quite an extensive list, but it is quite broad and does not reflect the ecological rarity that more modern varieties must have been for the next 20 million years.
The Big Freeze
Less than ten million years ago, the climate classified as Af by Wladimir Köppen, tropical rainforest, had receded to latitude 40 degrees, right by the Florida peninsula. Outside of that, grasslands and savannas continued to spread.
Only five million years ago, the cooling process that had been sloping downward for the last 40 million years now underwent a sharp, sudden decline to the extent of reducing the rainforests to their equatorial limits.
Ice had now covered 100% of the Antarctic continent. By itself, it wouldn’t have been enough to severely accelerate the cooling process.
But it wasn’t alone.
Both the Pacific and Caribbean plates sank beneath a submerged plateau, creating the uplift of a narrow landmass we’d recognize as Panama, Costa Rica, Nicaragua, Honduras, El Salvador, Guatemala and Belize. This creates a bridge connecting North to South America, resulting in a major detour of a warm ocean current that would later become the Gulf Stream. This newly-reestablished pathway wound up to the Arctic, icing the landmasses within the circle. As the Alps and Himalayas continued to rise, they amplified the process of chemical weathering, which made them even more conspirators in the cooling acceleration.
For the first time in eons, the ice age had returned, and lots of species were caught off-guard. This Big Chill, as it is colloquially called, lasted two Milankovich cycles (an average of 200,000 years) before life could get better adjusted to the colder climate. Half of all terrestrial species, and two-thirds of the marine species, became extinct. Casualty list:
ANGIOSPERMS
Celastrales
Huertales
Malvales
Gunnerales
Berberidopsidales
Santalales
Caryophyalles
Cornales
Icacinales
Metteniusales
Garryales
Boraginales
Vahliales
Bruniales
Acorales
Alismitales
Dioscoreales
Pandanales
Achariaceae
Balanopaceae
Caryocaraceae
Chrysobalanaceae
Euphorbiaceae
Goupiaceae
Humiriaceae
Ixonanthaceae
Ochnaceae
Pandaceae
Putranjivaceae
Rafflesiaceae
Trigoniaceae
Connaraceae
Elaeocarpaceae
Huaceae
Caesalpiniaceae
Quillajaceae
Ulmaceae
Cornynocarpaceae
Alzataceae
Crypteroniaceae
Melastomataceae
Aphloiaceae
Guamatelaceae
Picramniaceae
Burseraceae
Meliaceae
Rutaceae
Akaniaceae
Bataceae
Caricaceae
Pentadiplandraceae
Salvadoraceae
Tovariaceae
Tropaeolaceae
Sabiaceae
Clethraceae
Cyrillaceae
Ebenaceae
Lecythidaceae
Marcgraviaceae
Sapotaceae
Symplocaceae
Theophrastaceae
Loganiaceae
Sphenocleaceae
Oleaceae
Acanthaceae
Bignoniaceae
Linderniaceae
Plantaginaceae
Schlegeliaceae
Verbenaceae
Cardiopteridaceae
Pentaphragmataceae
Paracryphiaceae
MOLLUSCA
Cryptodonta
Limoida
Palaeoheterodonta
Arcoida
Hippuritoida
Arcticoidea
Cyamioidea
Glossoidea
Galeommatoidea
Mactroidea
Ungulinoidea
Veneroidea
Clavagelloidea
Myochamoidea
Pandoroidea
Pholadomyoidea
Thracioidea
Verticordioidea
ARTHROPODA
Branchiopoda
Aspidytidae
Liadytidae
Triaplidae
Hemiphlebioidea
Lestoidea
Calopterygoidea
Hagloidea
Schizodactyloidea
Pneumoroidea
Tanaoceroidea
Trigonopterygoidea
Colletidae
Diphaglossidae
Euryglossidae
Hylaeidae
Xeromelissidae
Nomiidae
Nomioididae
Rophitidae
Fideliidae
Embolemidae
Plumariidae
Cratomastotermitidae
Archotermopsidae
Archeorhinotermitidae
Stylotermitidae
Aetalionidae
Melizoderidae
Myerslopiidae
Clastopteridae
Epipygidae
Acanaloniidae
Achilidae
Achilixiidae
Gengidae
Hypochthonellidae
Tettigometridae
Tropiduchidae
Heteroptera
ACTINOPTERYGII
Enchodontoidei
Characiformes
Gymnotiformes
Osteoglossomorpha
AMPHIBIA
Ceuthomantidae
Telmatoboidae
Sooglossidae
Paratelmatobiidae
Kassinidae
Eleutherodactylidae
Phyzelaphrynidae
Strabomantidae
REPTILIA
Meiolaniidae
Corytophanidae
Tropiduridae
Amphisbaenia
AVES
Tinamiformes
Omnivoropteriformes
Dinornithiformes
Dromornithidae
Dontopterygiformes
Coliiformes
Opisthocomiformes
Trogoniformes
Cracidae
Teratornithidae
Plotopteridae
Bucconidae
Galbulidae
Scleruridae
Dendrocolaptidae
Furnariidae
Thamnophilidae
Thraupidae
Psophiidae
MAMMALIA
Tragulidae
Macroscelidea
Chlamyphoridae
Megatheriidae
Diatomyidae
Aplodontiidae
Tayassuidae
Hyaenodonta
Astrapotheria
Lipoterna
Pyrotheria
Callitrichidae
Aotidae
Pitheciidae
Tarsiidae
Nasalidae
Archaeolemuridae
Daubentoniidae
Lepilemuridae
Megaladapidae
Palaeopropithecidae
Lorisidae
Borophagidae
Percrocrutidae
Amphicyonidae
Machairodontidae
Hemicyonidae
Entelodontidae
Protoceratidae
Merycoidodontoidea
Chalicotheriidae
Tapiridae
Desmostylia
Nyctimenidae
Cynopteridae
Harpiyonycteridae
Rhinopomatoidea
Rhinolophoidea
Molossoidea
Nataloidea
Noctilionoidea
Gomphotheriidae
Mammutidae
Ice began to break past the polar circles and overwhelm the temperate zones. Sea levels dropped drastically, bridging lands together and destroying marine ecosystems.
Any large species or species specialized solely for warm, tropical climates wouldn’t stand a chance. But for others, the Big Chill was a godsend. Now they could get busy assuming their roles as top predators of the northern hemisphere. The cats that were stranded in Africa became today’s leopards, servals and caracals. Hyaenidae, ecologically rare for 20 million years, now spread out and became Africa’s top predators in the absence of the hyaenodonts. The split between toothed and baleen whales proved to be an advantage when the Big Chill hit.
Nevertheless, opportunity for the survivors wasn’t indefinite. The Great American Interchange was more sluggish on Great Lakes Earth, simply because Central America was just topographically difficult — twin chains of active volcanic mountains on narrow land surrounded by narrow shelves, making migration during a period of marine regressions frustrating.
