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A Stegomastodon skeleton from the Smithsonian Museum of Natural History

A Stegomastodon skeleton from the Smithsonian Museum of Natural History

One of the most compelling extinct creatures from South America is not as well-known as it should be because it suffers from an incredibly confusing name.  The amazing Stegomastodon was a mighty proboscidean which lived on the great grassy lowlands east of the Andes until modern times, which is to say until about 9,500 years ago (because  paleontologists have a very different definition of modern than, say, historians or artists).  Proboscideans of course are the astonishing order of large mammals which include elephants and their many extinct relatives like mammoths, mastodons, deinotheriums,  moeritheriums…and stegomastodons.  The stegomastodons first evolved in North America during the Miocene (about 3 million years ago) and they lumbered rapidly down through South America after the Great American Interchange when the Isthmus of Panama formed between the two continents.  In North America, the stegomastodons died out because of competition from the true mastodons, which crossed over from Asia via Berengia, however deep in South America, they found ecosystems which suited them and they lasted for a long, long time.

An illustration of a stegomastodon (from geologiadelparaguay.com)

An illustration of a stegomastodon (from geologiadelparaguay.com)

Stegomastodons are neither stegodons nor mastodons, two famous and well known genera of proboscideans.  Confusingly stegomastodons are the last of the gomphotheres.  Gomphotheres wandered into Asia, became isolated and evolved into Stegodons, which, in turn, are the probable ancestors of today’s still-living elephants (assuming you are still reading this in an age when the Chinese and poachers have not wiped elephants from the globe).  If these relationships are confusing to you, you can use the proboscidean clade below (but remember that the stegomastodons are gomphotheres and they lasted much longer than is shown on the chart).

wpid-photo-aug-10-2012-1957Stegomastodons were grazers: they lived on the immense fields of grass which flourished east of the Andes in what is now Paraguay, Uruguay, Bolivia, and Argentina. The creatures were smaller than modern elephants growing only to 2,8 meters (9 feet) in height and obtaining a mass of 6,000 kilograms (13,000 pounds).  It is not known what wiped out the last stegomastodons, but they died quite recently, just after the Younger Dryas stadial was ending…only shortly after humankind made its way to the southern parts of South America.

Skull of stegomastodon waringii

Skull of Stegomastodon waringii

Wooly Rhinoceros by Charles Knight (Los Angeles Natural History Museum)

Wooly Rhinoceros by Charles Knight (Los Angeles Natural History Museum)

Sadly, today the rhinoceroses are few on the ground.  There are only five extant species of the family Rhinocerotidae and none of them are doing well–because of habitat loss and humankind’s obdurate (and extraordinarily foolish) belief that rhino horns have magical supernatural powers. Yet once the rhinos were a mighty force—in fact, the largest land mammal ever, the Paraceratherium, was a sort of rhino.  There used to be multiple tribes of Rhinocerotidae, each containing numerous genera (which could in turn contain dozens of species) of these great horned perissodactyls. None of the extinct rhinos was more splendid that the magnificent wooly rhino (Coelodonta antiquitatis) which roamed Eurasia during the icy Pleistocene epoch and even survived (probably) up until the beginnings of human civilization.

The comparative size of a Wooly Rhinoceros

The comparative size of a Wooly Rhinoceros

A wooly rhinoceros was a substantial creature.  From fossils and mummified remains, we know they measured around 3 to 3.8 metres (10 to 12.5 feet) in length, and had an estimated weight of around 2,700–3,200 kg (5,999–7,000 lb)—so they were not much smaller than the still-living white rhinoceros (although wooly rhinoceroses are more closely related to the contemporary Sumatran rhinos—which do not become so big and heavy).  As you might guess from the name, wooly rhinoceroses had magnificent hairy coats to help them survive the cold and they had two large horns for defense and for mating displays.  For a long time, paleontologists have argued about whether the Coelodontas grazed grasses or browsed on tender shoots, berries, and mosses, but paleobotanical evidence (taken in tandem with fossilized skeletal features) now seems to indicate they were browsers, like bison or cows.

Wooly Rhinoceros (Illustration by Charles R. Knight, National Geographic)

Wooly Rhinoceros (Illustration by Charles R. Knight, National Geographic)

Wooly rhinos roamed the frozen steppes of Eurasia–a habitat which was much larger in those days due to the ice age and the lower sea levels of the Pleistocene.  For example, wooly rhinos could be found on the dry & icy wastelands of Southern England and they thundered across the cold plains which would later become the fertile hunting lands of Doggerland (which are now submerged beneath the North Sea).  They were also prevalent across northern Europe and down through Central Asia all the way to the Tibetan Plateau.

Wooly Rhinoceros from Chauvet Cave (ca. 30,000-32,000 years ago)

Wooly Rhinoceros from Chauvet Cave (ca. 30,000-32,000 years ago)

Based on cave paintings from tens of thousands of years ago, humankind seems to have had an early fascination with these great furry beasts.  Unfortunately the last wooly rhinos apparently went extinct around eight to ten thousand years ago (according to somewhat disputed carbon 14 readings from a specimen found frozen in the Siberian permafrost).  Many large species of Paleocene megafauna died off at approximately the same time: whether the great behemoths went extinct from humanity’s increasingly effective hunting, climate change, or from some great pandemic which affected large animals is unclear (although contemporary scientists have been inclining towards climate change as a primary cause).

Woolly Rhinoceros Hunt (diorama from Horniman Museum, London)

Woolly Rhinoceros Hunt (diorama from Horniman Museum, London)

Odobenocetops as digitally rendered by the BBC for “Chased by Seamonsters”

This blog has featured posts concerning saber-toothed seals and saber-toothed marsupials but did you know that the oceans around South America once contained a saber-toothed whale?  Odobenocetops lived during the Pliocene era (around 2.5 to 5 million years ago).  Two similar species are known in the genus from fossils discovered in coastal Peru.  An early member of the dolphin superfamily, Odobenocetops was probably more closely related to narwhals and belgugas then to modern dolphins and killer whales.

Measuring only a little longer than 2 meters (6 feet) in length, Odobenocetops was remarkable (at least among whales) for its flexible neck–which could turn 90 degrees.  The powerful blunt snout of the endearing little whale suggests that it fed from beds of mollusks and other bottom dwelling shellfish, which it rasped from their shells with a muscular tongue.  Additionally, the  Odobenocetopsidae had echolocation abilities like modern dolphins–although probably not so amazingly precise, since the extinct whales’ echolocation melons were much smaller than those of living dolphins.

Odobenocetops feeding

Of course the most distinctive features of Odobenocetops were their long spiky teeth running parallel along their sides.  Scientists speculate that these tusks could have been used to seek food or as a sensory organ–like the narwhal’s sensitive tusk.  Perhaps male whales used their tusks to battle for females, like walruses do (although they seem awfully brittle for such battles).   Some males had uneven tusks.  The sole known skull of a male Odobenocetops leptodon features a right-hand tusk 1.2 m (4 ft.) long, while the left-hand tusk is only 25 cm (10 in.) long.  Since this is the only male O. leptodon skull currently known,  it is unclear whether such asymmetry was normal.

It is striking that the whales’ saber teeth were held next to the body and it makes one think that the whale did not execute many sharp turns.  A humorous but somewhat sad cartoon which I found unattributed on the web demonstrates the potential drawbacks of the Odobenocetops’ striking saber toothed design.

Aww…the poor whale…

Andrewsarchus Skull at the American Museum of Natural History

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?

A toothy hairy model of Andrewsarchus

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).

A drawing of Andrewsarchus with a large ninja to explain scale (Picture Credit: Everything Dinosaur)

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.

A Delightful Andrewsarchus model/toy produced by Bullyland

Some scientists believe the creature was a hunter which 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!

An unpainted model of an athletic hunting Andrewsarchus (as envisioned by Paleocraft)

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 unclear.  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.

A digital Andrewsarchus pensively gnawing a bone beside the Eastern Tethys (from BBC’s “Walking with Beasts”)

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.

Diprotodon

The largest marsupial known to science is the now extinct diprotodon. Also known as the giant wombat or the rhinoceros wombat, this mighty marsupial grazer stood  nearly 2 meters (6 feet) tall and stretched 3 metres (9.8 feet) from nose to tail.  The animals flourished throughout much of the Pleistocene. From 1.6 million years ago until about 40,000 years ago, herds of Diprotodonts roamed across all of Australia.  These giant wombats were indeed closely related to today’s wombats and koalas: jointly such creatures make up the Vombatiforme suborder   Considering how formidable the bulldozer-like living wombat is, diprotodons must have indeed been like rhinoceroses and they probably occupied a similar top spot in the Australian web of life.

Unfortunately, like a substantial portion of Australia’s mega-fauna, the giant wombats disappeared shortly after humankind reached the island continent. The creatures apparently were destroyed by some combination of climate change, human hunting, and slash-and-burn land management. Aboriginal dreamtime lore makes extensive mention of a mighty furred beast called the bunyip–which has led anthropologists and paleontologists to speculate that the diprotodon has lived on in oral tradition for tens of thousands of years.

Fossil Remains of Diprotodon australis

Pronghorns

The second fastest land mammal is the pronghorn (Antilocapra americana), a delicate artiodactyl which ranges across the western wilderness of North America from Canada to the Baja deserts.  Although they look similar to antelopes, pronghorns are actually the last surviving species of the family Antilocapridae. They can run at speeds of up to 60 miles per hour and (unlike impalas or cheetahs) they can run at full throttle for a fair distance.

The Range of the Pronghorn

Pronghorns are named for their forked horns—which are not antlers but true horns made of bone with a layer of keratin.  They shed the hollow outer sheaths each year in late autumn and grow a new pair over the winter. Adult pronghorns stand 90 cm (three feet) high at the shoulders and weigh up to 50 kg (110 pounds).  Although pronghorns can run swiftly, they are poor jumpers.  Herds of pronghorns make great migratory treks across the country and face pressure from human developments and from fences (which they can’t jump over but must run under).  If you are a rancher in pronghorn country you might consider putting a non-barbed strand of wire as the bottom wire on your fence.

 

Two Pronghorn Bucks

Pronghorns once had many close relatives.  The Antilocapridae family is most closely related to giraffes but the different family members filled many of the same niches that bovids do in the old world.  These animals came in an array of shapes and were widespread across North America. There were once 22 varieties of antilocapridae (which you can explore here) but they died out ten to fourteen thousand years ago when the Clovis hunters arrived and slaughtered North America’s megafauna.

The distinctive head of Osbornoceros

Sick or injured pronghorns are sometimes preyed upon by wolves, coyotes, or cougars, but when they are healthy, adult pronghorns can easily outrun all contemporary North American predators. Their blazing speed is not an evolutionary extravagance: pronghorns once needed their swiftness to escape Miracinonyx trumani, the American cheetah which could probably run nearly as quickly as the living African cheetahs.  Like the avocado the pronghorn was molded to fit an ecosystem which has died out: today they are literally running from ghosts.

An American Cheetah Hunting a Pronghorrn

 

Obdurodon--A Miocene Platypus which flourished 15 to 20 million years ago

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.

An artist's reconstruction of Steropodon

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.

Another artist's vision of Steropodon galmani--Notice how peeved the poor creature looks!

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…

The Giant Echidna (Zaglossus hacketti) which lived until 20,000 years ago...

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.

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