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Different fossil plants and animals from the lacustrine deposits of the McAbee Flora of the Eocene (British Columbia, Canada)

Different fossil plants and animals from the lacustrine deposits of the McAbee Flora of the Eocene (British Columbia, Canada)

Today we return to the long-vanished summer world of the Eocene (the third epoch of the Cenezoic era). During most of the Eocene, there was no polar ice on Earth: a balmy temperate summer held sway from Antarctica to Svalbard. British Colombia was covered by a tropical rainforest where palm trees and cycads contended with warm weather conifers (and with the ancestors of elms, cherries, maples, and alders). Within this warm diverse forest, which thrived between 55 and 50 million years ago, lived numerous strange magnificent birds and insects. Shoals of tropical fish thronged in the acidic foaming waters (which were practically carbonated—since the atmospheric carbon dioxide levels of the Eocene were probably double that of the present).   The mammals of this lovely bygone forest were equally splendid–strange proto-carnivores not closely related to today’s mammalian predators,  weird lemur analogs, and strange ur-rodents. This week the discovery of two new mammal species was announced.  These remarkable fossil finds provide us with an even better picture of the time and place.

a reconstruction of the early Eocene  in northern British Columbia, a tapir-like creature from the genus heptodon with a while tiny proto-hedgehog in the foreground. (Julius T. Csotonyi)

a reconstruction of the early Eocene in northern British Columbia: a tapir-like creature (genus Heptodon) with a tiny proto-hedgehog in the foreground. (Julius T. Csotonyi)

One of the two creatures discovered was a tapir-like perissodactyl from the genus Heptodon. The newly discover tapir was probably about the size of a large terrier. I really like tapirs (and their close relatives) but these remains are not a huge surprise–since many perissodactyls thrived in North America during the Eocene. The other fossil which paleontologists found is a surprise—an adorable surprise! Within a stone within a coal seam was a tiny jaw the size of a fingernail. Such a fossil would have been all but impossible to study in the past, but the paleontological team led by David Greenwood, sent the little fossil to be scanned by a CT scanner and then imaged with a 3D scanner. The tiny jaw was from a diminutive hedgehog relative since named Silvacola acares.  The little hedgehog grew to a maximum adult size of about 6 cm (2.3 inches) long or approximately thumb-sized. Since it probably lacked spines, this miniature hedgehog was a bit different than the modern hedgehog, but it was definitely a relative.

As discussed in previous posts, I like to imagine the balmy Eocene, when so many mammals which are now the mainstay of our familiar Holocene/Anthropocene world got their first start. It makes it even better to imagine that the thickets were filled with endearing hedgehogs the size of bumble bees.

Rodhocetus (by Pavel Riha)

Rodhocetus (by Pavel Riha)

This endearing beasty is Rodhocetus, a long extinct proto-whale which lived during the mid-Eocene (approximately 40 to 50 million years ago). Rhodhocetus fossils are found in contemporary Pakistan, but the world has changed greatly since the warm Eocene: the creatures did not live on the tops of mountains, but rather in estuaries and shallow seas.

Rodhocetus

Rodhocetus

The early cetaceans shared ancestors with the artiodactyls (cows, pigs, hippos, goats, and suchlike even-toed ungulates) and indeed the first cetaceans, from the beginning of the Eocene, look somewhat like weird squashed hippos or water cows. By the middle of the epoch, however the familial similarities were beginning to fade.

06-14-P-02-G-01-KlausmeyerRodhocetus-full_1

Rodhocetus specimens have elongated hands and feet–which were almost certainly webbed. Their hipbones were not fused to their backbones, which gave them additional speed and maneuverability in the water, where they hunted for fish and squids. Although the creatures were adapted for an aquatic predatory lifestyle, they could still drag themselves up on land, unlike their descendents the modern whales and dolphins. Additionally they still retained fur, and double-pulley heelbones (the latter of which convinced paleontologists that whales and cows are relatives who share an ancestor).

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

Bullockornis (with human-size silhouette for comparison)

Bullockornis (with human-size silhouette for comparison)

My sincere apologies for being such a truant blogger last week!  Not only did I fail to post any new articles since Tuesday, I unpardonably left you stuck with nothing but the flimsy Ms. Perry during that time. In order to apologize, allow me to take you on a trip to the island continent of Australia…15 million years ago during the Middle Miocene. During this time one of the largest birds ever lived across Australia: a giant fowl named Bullockornis.

Bullockornis

Bullockornis

Bullockornis was a 2.5 meter tall (8 foot 2 inch) gooselike bird.  The creature weighed in at approximately 500 kilograms (1100 pounds) and scientists believe it was actually related to the modern geese and ducks.   If you have ever met a modern goose, you will realize that a goose the size of a bear would be a formidable creature indeed.  Additionally Bullockornis possessed a razor sharp beak with immensely powerful jaw muscles.  It is hard not to imagine the giant bird nipping off a he-man’s arms like corn kernels or biting through bridge cables with this monstrous beak, but the truth is scientists don’t know what the bird used it for.  The monstrous goose could have been a hunting carnivore (like certain ducks are today) or an herbivore which grazed on heavy dense plants.  Perhaps, like contemporary geese, it was an omnivore which hunted, grazed, and opportunistically scavenged whatever it could get.

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Bullockornis was discovered in 1979 but it only became well known when some PR savvy writer christened it the “Demon Duck of Doom”  (which strike me as a silly 1930s Disney-style name, but I guess whatever gets people involved in paleontology is good).  The scientific name “Bullockornis”  means “bullock-bird” but, even though the bird was the size of an ox, it is actually named for Bullock Creek (a rich fossil location in the Northern Territory).  Bullockornis was not the only giant of the Miocene in Australia.  The Bullock Creek fossil beds also contained fossils of Giant horned tortoises, marsupial “lions” (i.e. thylacoleonids) and grazing Diprotodontids—giant wombats (although nothing so large as the mighty Diprotodon which evolved in the Pleistocene).

Fossil Bullockornis Skull

Fossil Bullockornis Skull

Wadi Al-Hitan, Egypt

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.

Whale fossil at Wadi Al-Hitan

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.

Basilosaurus from “Life in the Ancient Seas Exhibit” at the Smithsonian Institution, National Museum of Natural History

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.

Detail from painting (Life in the Ancient Seas Exhibit: Smithsonian Institution, National Museum of Natural History)

During the Mesozoic, the age of dinosaurs, mammals were widespread, but they kept a low profile so as to avoid the baleful attention of the great reptiles.   A fossil of one of these furtive early mammals was discovered last November (2011) in Argentina.  The creature was christened as Cronopio dentiacutus, and not only does the animal’s partial skull give us a window into mammalian form in the late Cretaceous it also provides a special treat for regular readers of Ferrebeekeeper, for like the Smilodon, the walrus, and the Odobenocetops, Cronopio has distinctly pronounced saber teeth (despite being a small scurrying squirrel-like creature).

A model of the Cronopio dentiacutus–which was only 10 to 15 cm (4 to 6 inches) long.

Cronopio dentiacutus was probably actually more shrew-like than squirrel-like and used its saber teeth for hunting insects.  Based on its large eye sockets, Cronopio most likely hunted its prey at night (when it could also more easily escape the attention of the dinosaurs and other larger predators.

Julio Cortázar, Argentine Surrealist author

Cronopio dentiacutus takes its species name from a Greek phrase meaning sharp teeth, but the origin of its genus name is rather more literary.  The Argentine surrealist writer Julio Cortázar wrote several books about abstracted categories of fictional entities and the Cronopio was the idealistic but disorganized type of being (as opposed to rigid, highly-organized “famas” and indolent, dull “esperanzas”).  It is unclear what creative/idealistic features of this insectivorous early mammal struck the fancy of the discovering paleontologist to provoke such a name, but it is nice to see scientists pay Argentine belles-lettres such an acknowledgement.

A few weeks ago Ferrebeekeeper featured a post about belemnites, extinct cephalopods from the Mesozoic which teemed in immense schools through the reptile-haunted oceans of that bygone era.  Yet belemnites were certainly not the only cephalopods which swam in the Mesozoic seas.  Numerous shelled cephalopods—the ammonites—were widespread in every sort of marine habitat.  Ammonites are personal favorites of mine so I am not going to write a comprehensive explanation/description of the subclass.  Instead I wish to provide you with an idea of how big ammonites could get by providing a few pictures of large ammonite fossils which have been discovered.   Imagine these monsters jetting through the water with huge tentacles and big intelligent eyes scanning for giant predatory reptiles and you will have a better idea of the Mesozoic Oceans!

This one is only .7 meters (two feet) in Diameter but it sure is pretty.

An artist's depiction of a belemnite

This blog has already traveled back 400+ million years to the Ordovician, the era when great mollusks ruled earth’s oceans. The Ordovician ended in ice as Gondwanaland drifted into the Southern Polar regions—a tectonic shift which brought massive terminal cooling to the great reef systems of the time (and also fundamentally changed Earth’s climate and atmosphere), but the cephalopods were hardly done for.  They continued to evolve and adapt to the world’s ever changing oceans.  Today we pick up the cephalopod story hundreds of millions of years later during the Mesozoic era—the time of dinosaurs.

Artist's depiction of a belemnite school

The reefs and oceans of the Jurassic and Cretaceous were filled with nautiloid cephalopods—ram shelled descendants of the shelled tentacled monstrosities  from the Ordovician—but a new cephalopod had also evolved and filled up the shallow limestone seas in giant teaming schools.  These were the belemnites which lacked an external shell and superficially resembled squid.

Belemnites were distinct from today’s squids for several reasons.  Not only did they possess hard internal shells/skeletons composed of calcium carbonate but they also lacked the pair of specialized hunting tentacles present in modern cuttlefish and squid.  Instead the belemnites hunted with ten arms covered in tiny wicked hooks.

An Amzaingly well preserved fossil belemnite from the 155 million year old Jurassic Solnhofen limestones in Germany (notice the details of the animal's soft anatomy)

Belemnites fed on ostracods, crustaceans, and fish.  In turn they made up a sizeable portion of diet for, well, the sizeable predators of the time.  Fossils of plesiosaurs, pliosaurs, and giant sharks have been discovered with stomachs full of hooks or rostra. It is also thought that the dolphin-like ichthyosaurs survived largely on belemnites.  After feeding and digesting the mollusks, the ichthyosaurs probably vomited out the indigestible hooks and rostra of belemnites much in the manner that sperm whales expel the hooks of giant squid!

The bullet shaped rostra of belemnites have survived in vast numbers and are one of the most characteristic of all Mesozoic fossils.  These strange tapered cones weathered out of soft chalks nearly intact and proved extremely puzzling to people of past generations.  Numerous magical common names and magical folk beliefs grew out of the conical rocks. The English called the fossils “thunderbolts” and believed they were the physical leftovers from lightning strikes.  The ancient Scandinavians thought that belemnite rostra were candles dropped by gnomes, elves, and dwarves on the occasions they traveled from their realms through this world.  The ancient Chinese called them “sword stones” and believed they were imbued with ancient healing magic.

An opalized fossil of a belemnite rostrum

The end of belemnites was even more astonishing than these myths.  The creatures had short lives—which involved a larval phase drifting amidst the microscopic plankton.  The immense extraterrestrial bolide which struck the Earth at the end of the Cretaceous ended the dinosaurs and also finished off the belemnites. The little larvae were unable to survive the massive planktonic die-off which accompanied the long dark winter following the strike.  Fortunately other cephalopods proved hardier–and the most intelligent mollusks continued to change and adapt right up until today.

An artist's depiction of the Chickzalub bolide impact

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…

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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