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Camelids are believed to have originated in North America. From there they spread down into South America (after a land bridge connected the continents) where they are represented by llamas, alpacas, vicuñas, and guanacos. Ancient camels also left North America via land bridge to Asia. The dromedary and Bactrian camels are descended from the creatures which wandered into Beringia and then into the great arid plains of Asia. Yet in their native North America, the camelids have all died out. This strikes me as a great pity because North America’s camels were amazing and diverse!
At least seven genera of camels are known to have flourished across the continent in the era between Eocene and the early Holocene (a 40 million year history). The abstract of Jessica Harrison’s excitingly titled “Giant Camels from the Cenozoic of North America” gives a rough overview of these huge extinct beasts:
Aepycamelus was the first camel to achieve giant size and is the only one not in the subfamily Camelinae. Blancocamelus and Camelops are in the tribe Lamini, and the remaining giant camels Megatylopus, Titanotylopus, Megacamelus, Gigantocamelus, and Camelus are in the tribe Camelini.
That’s a lot of camels–and some of them were pretty crazy (and it only counts the large ones—many smaller genera proliferated across different habitats). Gigantocamelus (as one might imagine) was a behemoth weighing as much as 2,485.6 kg (5,500 lb). Aepycamelus had an elongated neck like that of a giraffe and the top of its head was 3 metres (9.8 ft) from the ground. Earlier, in the Eocene, tiny delicate camels the size of rabbits lived alongside the graceful little dawn horses. This bestiary of exotic camels received a new addition this week when paleontologists working on Ellesmere Island (in Canada’s northernmost territory, Nunavut) discovered the remains of a giant arctic camel that lived 3.5 million years ago. Based on the mummified femurs which were unearthed at the dig, the polar camel was about 30 percent larger than today’s camels. The arctic region of 3.5 million years ago was a different habitat from the icy lichen-strewn wasteland of today. The newly discovered camels probably lived in boreal forests (rather in the manner of contemporary moose) where they were surrounded by ancient horses, deer, bears and even arctic frogs! Testing of collagen in the remains has revealed that the camels are closely related to the Arabian camels of today, so these arctic camels (or camels like them) were among the invaders who left the Americas for Asia.
The bones are a reminder of how different the fauna used to be in North America. When you look out over the empty, empty great plains, remember they are not as they should be. All sorts of camels should be running around. Unfortunately the ones that did not leave for Asia and South America were all killed by the grinding ice ages, the fell hand of man, or by unknown factors.
The largest land animal alive today is the mighty African elephant, however even the largest adult bull elephants were dwarfed by the largest land mammal ever to exist. The giant herbivore Paraceratherium stood 5.5 metres (18 ft) tall at the shoulder. When standing upright the creature’s head (which was approximately the same size as character actor Danny Devito) was about 8 metres (26 ft) above the ground. Although debate continues about how much the beast weighed, reasonable estimates suggest it could have massed from 15 to 20 metric tons which means that the animals were as large as mid-sized sauropod dinosaurs from the previous era. Partial skeletons of Paraceratherium were discovered by different scientists at different times–which has confusingly resulted in three different names for the genus: 1) Paraceratherium which means”near horn animal” in Greek; 2) Indricotherium which was derived from a mythical Russian progenitor-monster called the Indrik-Beast; and 3) Baluchitherium which means “Baluchistan beast”, in honor of Baluchistan, an arid portion of the Iranian plateau, where a fossil specimen was unearthed. Paleontologists prefer to call the genus “Paraceratherium,” however, thanks to TV specials and museum shows the name “Indricotherium” remains popular with the public.
Paraceratheriums were perissodactyls. The giant creatures were most closely related to the living rhinoceroses (although they shared ancestors with tapirs and horses as well). Paraceratherium’s immense size allowed it to eat the branches and leaves of large trees. They ranged across what is now Central Asia across Iran, India, Pakistan, Mongolia, Kazakhstan, and China. The various species of Paraceratherium had long graceful necks somewhat like that of Okapis. Additionally they possessed nimble elongated upper lips with which to strip leaves off of branches. These lips were no quite trunks but probably resembled the long grasping snout/lips of tapirs. Although Paraceratherium was closely related to rhinoceroses, they lacked the rhino’s characteristic horns—their giant size meant they did not need them. The genus originated in the Eocene and flourished during the Oligocene—a golden age of perissodatyls. However as the global cooling became more pronounced in the late Oligocene, the great creatures gradually vanished.
Imagine standing high above planet Earth and looking down at the blue and white band of seas surrounding Antarctica. You are looking at one of the most important features of the Earth’s surface. The turning of the planet and strong westerly winds drive the cold deep waters of the Southern Ocean into the planet’s largest and most powerful current system, the Antarctic Circumpolar Current (ACC). The clockwise current isolates the frozen continent into its own self-replicating climate. Since there are no great land masses lying in the ring of open water at these latitudes, the ACC also forces waters from the ocean depths up to the surface. This upwelling brings rich nutrients from the depths and causes immense blooms of phytoplankton (which in turn nurture life throughout all the world-ocean). Additionally the current stirs the circulation of the Atlantic, Pacific, and Indian Oceans.
The ACC has been known to sailors for centuries. A sailing ship can travel west along the current with great speed (if the sailors have the bravery and stamina to confront the fierce winds of “the roaring forties”). The “clipper route” was the fastest sailing route around the world, but it was dangerous. The three great capes (Cape Horn, the Cape of Good Hope, and Cape Leeuwin) all claimed innumerable lives as did wind, ice, and storm. Today the clipper route has been abandoned as self-powered ships bring their cargoes of plastic junk straight across the ocean from China (and then cut across the Panama Canal) but sailing enthusiasts still recognize the fastest way to ride the wind around the planet. The major circumnavigation sailboat races all travel the clipper route.
The true history and significance of the ACC vastly exceeds the paltry recent concerns of navigation and world trade. Geologists estimate that the ACC current began spinning around 34 million years ago at the end of the Eocene epoch as Antarctica split from Australia and drifted further south. When still connected, Antarctica and Australia had been a place where cold southern water and chill weather mixed together with tropical warmth—thus causing the whole planet to warm up. However when Antarctica drifted south, it started a series of climate feedback loops. The oceans around the continent began to freeze and ice started to build up on the mountains. An entire continental ecosystem began to change in the cold. The tropical forests (which had been filled with strange marsupials) began to die and become tundra. As the Oligocene progressed and Drake’s Passage widened, the rivers–once filled with catfish–turned to ice. The landmasses of Antarctica became crushed down under immense glaciers. Antarctica died in the cold. By 15 million years ago it was as it is now, home to only tardigrades, lichen, and a handful of visiting birds and seals.
Even now the Antarctic Circumpolar Current still isolates the continent from the warmth of the rest of the world. Yet through upwelling of iron and other nutrients, the current bolsters an immense fecundity of phytoplankton–the great primary producer of the ocean. Masses of copepods and krill feed on the algae and the diatoms and they in turn are eaten by fish, mollusks, mammals, birds, filter feeders…everything. The great southern oceans are among the most diverse and strange habitats for living things. It is there that the largest mollusk on the planet is found—which is the subject of an upcoming post.
Our story takes us back 37 million years ago to the hot moist swamps of the Eocene (again). In the swamps of Africa lived a long low wallowing mammal 3 meters (9.8 feet long) and 70 centimeters (2.25 feet) tall. This swamp dweller occupied the same sort of niche now taken by pygmy hippos and capybaras—it was an amphibious grazer which lived on soft water plants and could slip into the water to avoid land predators (and vice versa). The animal was named Moeritherium, a genus consisting of several similar species, all now long extinct.
Moeritheriums mostly had peg like teeth for grinding up vegetation, but the creatures’ second incisor teeth were elongated like daggers for display, defence, and rooting. So Moeritherium was really another saber toothed creature (like walrus, Smilodon, and Odobenocetops), but we never think of their closest living relatives as saber-toothed so it is hard for me to think of them that way. In fact Moeritherium’s closest relatives overshadow all the details about the low-slung swamp-dwelling creature entirely because they are one of the most magnificent and intelligent orders of creature on planet Earth. The Moeritheriums wallowing in the African swamps long ago were among the very first Proboscideans–an order of mammals including elephants, mammoths, mastodons, and gomphotheres.
Moeritheriums probably did not have a long trunk like today’s elephants, but they did have a long flexible upper lip like tapirs. Their eyes and ears were high up on their head so they could submerge themselves but still watch the surrounding landscape. They were not direct ancestors of the elephants and mammoths but instead descended from a common ancestor, Eritherium, a rabbit sized progenitor, which was rather like a hyrax. Moeritheriums were highly successful in their day, but they disappeared as the Eocene climate dyed up and cooled down. Fortunately several other families of proboscideans like the paleomastodons and the Phiomias were there to carry on the magnificent order of Proboscideans.
In the desolate desert 150 kilometers southwest of Cairo there is a fearsome arid valley (wadi) of cliffs, carved buttes, and sandblasted erratic boulders. The bleached landscape has an otherworldly emptiness as though it were located on a lifeless alien planet, though if you look closely, the desert is filled with austere furtive life like dorcas gazelles, tiny sand colored lizards, cobras, scorpions, and fennec foxes. The name of the place is even more otherworldly—“Wadi Al-Hitan” which is Arabic for “valley of the whales” and although the great smooth rocks buckling out of the sand might momentarily be taken for the backs of huge whales, the utter absence of the ocean (or of water of any kind) makes the name seem fanciful. The nearby Mount Garet Gohannam (which means mountain of hell because of the way it glows like flames at sunset) seems to be more aptly named.
However the name of Wadi Al-Hitan is remarkably literal–for the valley contains the remains of hundreds of huge ancient cetaceans which died in the Eocene and were fossilized in the yellowish sandstone. Forty million years ago the valley was a marine lagoon. Although the remains of numerous sirenians, sawfish, sharks, rays, sea turtles, marine crocodiles, sea snakes, and even swamp dwelling moeritheriums have been discovered in the wadi, the valley takes its name from the most spectacular and numerous fossils which belong to four different species of primitive whales. The most commonly discovered fossils belong to Dorudon, which was 3-5 meters long (9-15 feet) and fed on fish and mollusks, and to Basilosaurus, which was 15-22 meter (50-72 foot) and fed on everything else in the ocean.
Basilosaurus was first discovered in Louisiana in the early 19th century. Its immense size and serpentine form initially convinced naturalists that it was a marine reptile and they misnamed the creature Basilosaurus (which means “king lizard”). The mistake soon became obvious and Basilosaurus was classified among the Archaeoceti, a paraphyletic suborder of the cetaceans, however the giant kept its dinosaur name. Different species of Basilosaurus flourished in oceans worldwide during the wet, tropical Eocene and, even though they were obviously very adept at ocean living (indeed rising to the top of the food chain) the creatures betray vestiges of terrestrial living which modern whales have entirely dispensed with. Not only do Basilosaurus fossils have teeth and jaws which retain reatures from their artiodactyl ancestors, they also have tiny vestigial back legs a mere half meter in length (which would scarely help a 22 meter animal get around). Additionally Basilosaurus was different from modern whales in that it probably moved with eel-like horizontal thrashing of its long tail (modern whales move their flukes vertically). Basilosaurus probably did not dive very deeply, but moved about near the surface of the oceans hunting for smaller marine animals.
Although Wadi Al-Hitan was discovered by Europeans in 1902-1903, some archaeologists and anthropologists have speculated that it was known long before that and have been irresistibly drawn towards comparing basilosaurus with the giant crocodiles and earth spanning serpent gods which populate ancient Egyptian cosmology.
In the summer of 1923, Kan Chuen Pao, unearthed an enormous skull from the baking Gobi desert of Mongolia. Pao was a member of a paleontology expedition led by Roy Chapman Andrews, a world famous explorer, adventurer, and naturalist who, during the course of his career, rose from being a janitor at the American Museum of Natural History to being its director. The skull they found was an enigma—the creature was a mammal with immensely powerful jaws but blunt peg-like teeth. No substantial bones were found other than the skull sans jaw (nor have any further specimens ever been discovered). The skull was discovered in sediments deposited during the late Eocene, the sweltering summer epoch when most extant mammalian orders evolved, so it is probably 36 to 40 odd million years old. Andrews was immediately of the opinion that it was a huge carnivore, but what sort of creature was it really?
The creature was named Andrewsarchus mongoliensis in honor of Adrews and his expedition. Andrewsarchus may have been the largest mammalian carnivore ever (although short faced bears might have been larger). The one skull, currently in New York, measures 83 cm (33 inches) long and 56 cm (22 inches)wide–which suggests the animal may have been 3.4 meters (11 feet) long and nearly 2 meters (6 feet) tall at the shoulders. Such a creature could weigh more than 1000 kg (2200 lb).
But Adrewsarchus may not have been a carnivore: ever since the beginning of the jazz age, Paleontologists have argued about the monster’s diet. Andrewsarchus lived along the coast of the eastern Tethys Ocean, a sea which was dried out and destroyed when the Indian subcontinent barreled into Asia during the late Eocene/Early Oligocene.
Some scientists believe the creature was a hunter who captured the giant land animals of the time. Other scientists believe the animal was a scavenger which lived on the rotting carcasses of primitive whales and beached sea turtles. Another group feels that the creature fed on huge beds of shellfish, and a final school holds that the animal was even larger than believed and was at least part-herbivore!
The taxonomy of Andrewsarchus is equally confusing. The great skull was initially classified as a giant creodont (an extinct order of alpha-predators which share an ancestor with today’s carnivore). The first scientific paper about the creature by great paleontologist and…um eugenicist Henry Fairfield Osborn states, “An outline sketch of the skull was sent in a letter to the Museum, from which Dr. W. D. Matthew immediately observed its real affinity to the primitive Creodonta of the family Mesonychidae.”
Later scientists have been less certain about lots of things than Osborn was and Andrewsarchus’ place in the mammalian family is now uncertain. A consensus is emerging that the great creature shared common ancestors with the artiodactyls (like hippos, deer, and pigs). Perhaps its heritage provides insights into the link between the artiodactyls and their close (yet oh so distant) cousins the whales.
Whatever the case is, these giant hoofed creatures with their immense powerful maws must have been amazing and terrifying to behold. Their fate seems to have been sealed as the Tethys closed and the Gobi basin dried out, but whenever I think of the harrowing deserts of Mongolia and China, I imagine their fearsome toothy spirits towering over the other strange ghosts of that haunted place.
Ferrebeekeeper has an abiding interest in monotremes including both the poisonous platypus and the enigmatic echidnas (with their advanced frontal cortex). But sadly that is about it as far as it goes for the extant egg-laying mammals: there are only two living families of monotremes (with a scanty total of five species split between them). To learn more about these animals one must turn to paleontology. Unfortunately even in the fossil record, monotremes are extremely rare.
Based on genetic evidence, biologists believe that the first monotremes made their advent in the history of life about 220 million years ago during the Triassic era; however the earliest known fossil monotreme so far discovered was a fossil jaw from the early Cretacious era about 120 million years ago. The bones belonged to Steropodon galmani, which seems to have been a beaked swimmer about 50 cm (20 inches) long which lived in Australia. Steropodon was apparently a giant among Cretacious mammals–most of which seem to have been shrew-sized (so as to better avoid attention from their contemporaries, the dinosaurs). Reconstructions of Steropodon all seem to resemble the platypus, and most paleantologists would probably concede that it was a sort of platypus—as apparently were other Mesozoic fossil monotremes such as Kollikodon and Teinolophos (platypuses and these platypus-like forbears are called the Ornithorhynchida). During the Cretaceous era, the land which is now Australia was in the South Polar regions of the world (approximately where Antarctica is today). Although temperatures were much warmer during the Cretaceous, monotremes must still have been able to deal with terrible cold: it is believed that the extremely efficient temperature control and the deep hibernation mechanism which these animals continue to display first evolved during that time.
The only monotreme fossil which was not found in Australia was from another platypus-like creature named Monotrematus sudamericanum. The creature’s remains were found in a Patagonian rock formation from the Paleocene era (the era just after the fall of the dinosaurs). Monotremes probably flourished across South America and Antarctica, as well as on Australia, but evidence is still scarce. There are most likely many interesting monotreme fossils throughout Antarctica, but, for some reason, paleontologists have not yet discovered them. Additionally, unlike the marsupials (which still quietly flourish throughout South America), the poor monotremes were wiped out on that continent.
Last week I wrote about the Eocene era and the great proliferation of mammalian types which took place during that warm and fecund time. Although most families of mammals alive today first appeared on the scene during the Eocene, obviously the monotremes were already incredibly ancient. The Eocene does however seem to have been significant time for the monotreme order: the aquatic platypuses were apparently the ancestral monotremes, and echidnas (the Tachyglossidae) probably split off from them during the Eocene. Unfortunately we have no Eocene monotreme fossils so this conclusion is based on genetic evidence and on the suffusion of Miocene monotremes which include representatives of both Ornithorhynchida and Tachyglossidae. Some of these latter creatures are spectacular, like Zaglossus hacketti the giant echidna from the Pleistocene which was about the size of a ram! As Australia dried up so did the monotremes and now there is only one species of platypus left…
Well, that’s a cursory history of the monotremes based on what we know. I wish I could tell you more but unfortunately there is no fossil evidence concerning the first half of the order. Sometimes I like to imagine the first monotremes—which were probably clunky, furry platypus-looking characters with an extra hint of iguana thrown in. These creatures fished in the alien rivers of the Triassic world in a time when dinosaurs and pterosaurs were also still evolving.
The Eocene epoch (which lasted from 56 million ago to 34 million years ago) was hot! Temperate forests ran all the way to the poles. Steamy tropical jungles grew in the latitude where Maine is now and the equatorial regions of earth were (probably) sweltering. Tropical reefs formed in the coastal waters around a heavily forested and ice-free Antarctica. Since there was not year-round ice at each pole, the sea levels were much higher.
The Eocene was a time when most of the contemporary mammalian orders first appeared. The earliest artiodactyls, perissodactyls, rodents, bats, probiscideans, sirenians, and primates all originated during this time. Of course mammals were not the only story: the Eocene was also a time of great diversification for birds and many familiar orders of avians developed then. Reptiles begin to put the setbacks which marked the end of the Cretaceous behind them and several giant new species emerged including an immense tropical ur-python and a host of crocodiles and turtles. It is harrowing to think that the first wee dawn horses and cute little early atiodactyls were forced to contend with a 13 meter long super snakes and giant crocodilians (which flourished in the great hot swamps of Alaska), but such is the case.
The high temperatures of the Eocene are perplexing to scientists. By contrast, the temperatures of the Paleocene (which was the first era of the Cenezoic and had directly preceded the Eocene) were much more temperate. In fact the temperature spike of 56 million years ago seems to have ended the Paleocene and brought about the diversification of Eocene life. The rapid warming is known as the Palaeocene-Eocene thermal maximum and scientists have been vigorously debating what caused the climate change. An immense amount of carbon seems to have entered the atmosphere at this time, which in turn led to greenhouse warming. It remains controversial as to how such a large quantity of carbon got into the atmosphere. Comet/meteorite impact, massive peat fires, and volcanic activity have been suggested as triggers, however supporting evidence is lacking. The release of globally significant quantities of hydrocarbons–which had been trapped in undersea clathrates seems like a more feasible hypothesis, as does the idea that the earth’s orbit brought the planet closer to the sun for a time.
The end of the Eocene was also linked to the carbon cycle. Reduced carbon dioxide in the atmosphere seems to have led to global cooling and newly evolved varieties of grasses began to invade large swaths of the world. Additionally two massive meteor strikes in Siberia and Maryland combined with substantial volcanic activity to finish off the long hot summer. But during the Oligocene, the era which followed the Eocene, the world was a much more familiar place inhabited by orders of animals which are still here with us today (or are us–since primates first evolved during the Eocene).