Fascinating furred creatures of Australia's past
NOBODY SEEMS TO KNOW exactly when an unknown beachcomber, strolling along the sand at the base of Tasmania's picturesque but rugged promontory known as Fossil Bluff, near Wynyard, made his serendipitous find. Chancing upon a chunk of ancient marine sandstone lying on the sand, the discoverer, recognizing certain projecting pieces as consisting of fossilized bone, picked it up. Later examination revealed a damaged but relatively complete skeleton of a mammal. Not being a marine animal, its carcass must have fallen into the water and drifted to its burial site.
The discoverer could not have realized at the time that he would go down anonymously in Australian paleontological history as the discoverer of what would remain for many years the oldest known Australian marsupial. The scientific community did not become aware of its existence until it surfaced in a private collection around 1862. Even then its significance was not realized. Not until many years later, after being studied and named Wynyardia bassiana by Sir Baldwin Spencer at the turn of the century, did it receive serious attention. For many years more, its authenticity as an extinct ancient beast was doubted by some; doubt was erased when its ancientness was unequivocally established by Edmund Gill in 1954, its age being put at somewhere between 19 and 23 million years old. Its status as the oldest Australian marsupial has since been usurped by a progression of finds pushing back Australia's mammal fauna to the middle of the Cretaceous period (136–65 mya1) when dinosaurs still stalked the earth. (See Ages of Creation.)
This article deals mainly with the past 65 million years, known technically as the Cainozoic era or, more popularly, the “age of mammals”; no dinosaur remains have been found among rocks of this era. It is divided into two periods — the Tertiary period (65–2.5 mya) and the Quaternary or Pleistocene period (2.5 mya to present). The Tertiary is further subdivided into epochs: Palaeocene (65 to 55 million years ago), Eocene (55 to 38 mya), Oligocene (38 to 25 mya), Miocene (25 to 5 mya), and the Pliocene (5 to 2 mya).
Knowledge of Australia's extinct creatures, as is true in much of the rest of the world, is growing at a rapid pace. (For some reason, few fossils earlier than Pleistocene have been found in Western Australia.) In recent years, it has been dramatically extended by discoveries in a number of locations, particularly at Boat Mountain near Murgon in southeast Queensland and Riversleigh Station in northern Queensland. Due to a high limestone concentration in the ponds and waterholes at Riversleigh at that time, preservation of bony tissues there is of an exceptionally high quality. The description of Long and others can hardly be improved upon for giving the flavor of the world of furry creatures revealed by such discoveries:
The fossil mammal faunas of Australia are mysterious, often bizarre, and still full of surprises as new research uncovers many previously unknown species every year. This land once contained giant sloth-like marsupials with trunk-like noses, carnivorous giant rat-kangaroos with dagger-like lower incisor teeth, giant lumbering plant-eaters nearly 3 meters long and ferocious pouched carnivores with blade-like shearing teeth (Long, Archer, Flannery & Hand 2002, p. 9).
Join us on an eye-popping journey into their world. And please bear this vital point in mind. Many more creatures await discovering, or have left no traces, than the ones that have been found.
Tales tiny teeth tell
Big trees out of little acorns grow, and big leaps in knowledge out of tiny teeth flow. We uninitiated find it hard to appreciate the quantum leaps in knowledge that often are based on a single bone or tiny package of dentine and enamel that is a tooth. The reason a single tooth can prove so enlightening is that teeth from each kind of animal come with a staggering array of unique characteristics. For instance, consider Wroe's description of Ganbulanyi's teeth:
Dasyurid in which the protocone shows a greatly reduced occlusal surface area and a bulbous base with the lingual face steeply inclined, the centrocrista is straight in occlusal view, the postmetacrista is aligned anteroposteriorly, stylar cusp C is present, the major cusps are approximated (i.e., paracone and metacone, the paracone and stylar cusp B, and the metacone and stylar cusp D respectively are at least partially fused), the stylar shelf is greatly reduced, and both the upper molar (M 1 or M 2) and premolar (P 2 or P 3) are massive but low- crowned (1998, p. 1).
The anatomy of teeth — size and shape, position in the jaws, minute-scale “topography” of tooth surfaces — have to be perfectly suited by precision engineering to the purposes they are to serve. Rough enough is absolutely not good enough. The staggering precision of various tooth types makes each one unique and enables researchers, by comparison with dentitions (arrangement and structure of teeth) of living creatures, to tell at least in general terms what sort of animal it was.
Of course, this rule doesn't apply when completely unique teeth are found. For instance, the teeth of extinct Ektopodontids (mentioned later) have highly unusual, complex molars in which the cusps are arranged in transverse rows and are supported by special struts and ribs. Without anything to compare them with experts are guessing as to what Ektopodon looked like; all they can tell us is that, based on the design, the animal probably ate nuts and seeds and that, based on size, it was a medium-sized creature.
Imagine the satisfaction God derived from crafting thousands and thousands of discrete, unique sets of teeth, each one perfectly designed for its owner's needs. (Unless, of course, the big bang produced the supposed miracle-working power of mutation and natural selection which in turn designed a myriad of precise dentitions, each perfectly adapted to its owner's unique mode of life.)
So the discovery at Riversleigh in 1997 of a molar and a premolar tooth of a bone-cracking dasyurid from deposits of the late Miocene tells us a lot. It pushes back the habit of bone-crushing by some millions of years compared with previous knowledge. The find makes Ganbulanyi djadjinguli, similar to the living Tasmanian devil, the smallest bone-cracker known (Wroe, p. 1).
Details of where such teeth are found and of other creatures found in the same strata of rock enable experts to piece together a fairly accurate picture of the environment at the time and how various animals interacted with each other — who ate whom, whether they lived in water, on or under the ground, in trees, and so on.
Australian mammals from the age of the dinosaurs
While northern hemisphere lands have divulged evidence of mammals and mammal-like creatures, such as the strange morganucodontids, going back as far as 225 million years (compared with 245 million years for the earliest dinosaurs), until very recently Australia's oldest-known mammal, Wynyardia, went back only to the early Miocene, about 25 million years ago. As late as 1983 experts spoke of the lack of early fossil mammal material from Australia as a “maddening puzzle” but were in a lather of anticipation as a result of a report that fossil fleas from the late Cretaceous (about 70 mya), with mouthparts designed for dining on mammals, had been discovered in sediments in Victoria (Quirk and Archer 1983, p. 14).
A mere two years later, Wynyardia was unceremoniously unseated from its throne, and the reliability of the flea clue proven, when a dealer poured out a collection of fossils he had purchased from an opal miner at Lightning Ridge in New South Wales onto a hotel bed to be inspected by Alex Ritchie, Curator of Fossils at the Australian Museum. Ritchie immediately noticed something special — an opalized lower jawbone, with about six intact teeth, that bore all the signs of Mesozoic (225–65 mya) antiquity.
The first of the two Mesozoic fossils came from rock about 110–115 million years old, meaning that whatever it was, it predated our friend Tyrannosaurus by many millions of years. (T rex may have lived for only about two million years at the very end of the age of dinosaurs.) The teeth were a dead give-away; they belonged to a toothed platypus-like creature that paleontologists named Steropodon. Although today's platypus has teeth only while immature, the teeth in the specimen are so similar to these "milk teeth" that its identification as some kind of platypus or platypus-like beast goes undisputed. Without further discoveries, we can have no idea how widespread this creature was, or how long the species existed. (Intriguingly, in 1991 a fossilized platypus tooth was found in strata about 60 million years old in Argentina.) Steropodon lived in an estuary of a large river that emptied into a huge inland sea to the north and shared its world with dinosaurs, crocodiles, small turtles, and who knows what else.
The second discovery occurred in 1997 near Inverloch, about 125 kilometers south-east of Melbourne, and consisted of a jaw and some teeth. Paleontologists named this little beauty Ausktribosphenos nyctos — we'll call it “Ausk” for short. This discovery, together with a later one of a creature named Bishops, has sent paleontologists into a tizz. To understand why, one needs to know just a little about the different groups of mammals. Although some classification systems describe up to 25 orders (a basic unit of classification) of mammals today, most systems peg it at nineteen. These nineteen orders can be divvied up into three higher levels of classification. Two of the categories (marsupials and monotremes) each contain only one of the nineteen orders. The other seventeen orders can all be lumped together into the third category known as placentals.
Monotremes — the platypus and echidnas — are found only in Australia and New Guinea today. What sets them off from all others is their method of reproduction — they lay eggs. Marsupials differ from placentals in that marsupial young are born at a very early stage of development ("baby" kangaroos, for instance, are only the size of a peanut when born, while Tasmanian devils are barely larger than a grain of rice) and then migrate to the mother's pouch where they attach themselves to a nipple, complete their development, and spend a varying amount of time until they are ready to face the big wide world. Few sights are cuter than a “joey” kangaroo poking its little head out of mom's pouch. Placentals, on the other hand, undergo all the development they need in the uterus before being born at a relatively advanced stage. The marsupial method of reproduction seems ideally suited to the vicissitudes of Australia's feast or famine climate. In good years, the joey-on-nipple method of reproduction leads to a rapid increase in population, something that large placentals generally cannot achieve. In bad years, the small investment of maternal nutrients in tiny young that die if deprived of milk while on the teat means that wastage is kept to a minimum.
Australia is the stronghold of marsupials and monotremes, playing host to about 180 species of marsupials, compared to about 80 species of marsupial opossums and opossum rats in South America and one species of opossum in North America. But Australia is truly a pauper continent when it comes to placentals; of the nineteen placental orders of mammals, it has representatives from only two — rodents and bats. According to the fossil record, bats first made their home in Australia about fifty million years ago, and rodents such as the water rats, so beloved by European women in the early twentieth century for their luscious fur, only about five million years ago.
Here's the rub: Ausk teeth fit the placental mould, not the marsupial mould! More, its age is practically identical to the toothed platypus mentioned earlier — 115 million years. Its characteristics identify it as some kind of tiny, insect-eating, shrew-like animal. If those researchers who claim they are placentals are correct, “then our understanding of how placental mammals arose and spread around the world is seriously flawed” (www.abc.net.au/science). Theories about the origin and spread of animals, particularly theories based on evolutionary biases, can dramatically change with one small discovery! (The discovery in Madagascar at almost the same time of a tiny jaw fragment a few millimeters long of Ambondro mahabo, dated at 167 million years old, has further deepened the controversy among evolutionists as to the where and when of mammalian origins.)
Those familiar with the works of God are not surprised by surprises; they expect them and relish every one as yet another proof of the capacity of God for infinite thought. Indeed, you can almost hear a chuckle from heaven when you read about the bafflement experienced by evolutionists at some of the “contradictions” between current and ancient distributions of animals. Indeed, the modern distribution of animals bears little resemblance in many ways to earlier times. The original stronghold of marsupials was North America! For most of the Cretaceous period (135– 65 mya), marsupials were the dominant mammal type on that continent, the placentals only arriving there about five million years before the period ended (Dawson 1977, p. 78). (Until about 2 to 3 million years ago, South America rivaled Australia for diversity of its marsupial fauna; many mammals died out, including two complete orders, when a land bridge developed between North and South America, leading to what Stephen Jay Gould described as “the most devastating biological tragedy of recent times” [1980, p. 240].). Paleontologists suggest that Australia's marsupials arrived there in waves from North America, via South America, at the end of the Mesozoic. Marsupials then vanished from North America. Tralaa! A switcheroo to match all switcheroos, sometimes called “The Great Faunal Interchange”. However, since the North America marsupials were quite different from Australia's marsupials, logic suggests creation is the real answer to the puzzle.
Similarly, paleontologists are puzzled by the evidence that elephants may once have lived in Australia. Fragments of tusk material now housed in the Natural History Museum in London are described as having been found in the Darling Downs region of Queensland, while a smaller tusk has supposedly been found along the West Australian coast. Some experts are so troubled by the thought that elephants once roamed Australia that they question the authenticity of these finds.
Getting back to Ausk, we must not jump the gun on its significance, as researchers are not at all unanimous in their opinion about its placental placement:
The recently discovered Cretaceous mammal Ausktribosphenos nyctos may be, as it was first described, the earliest placental mammal, which would suggest an origin for that group in Gondwana, or it could represent a completely different group of mammals… (Long and others, p. 208).
Some researchers claim Ausk and Bishops remains should be classified as monotreme in nature. The discovery of more tiny jaws and teeth from a creature dubbed Teinolophos, which most researchers agree belonged to another extinct monotreme, may support the contention that Ausk and Bishops are not revolutionary placentals after all. Nobody, it seems, considers the simple possibility that such creatures were created by God for that time and place for reasons He alone understands. In their zeal for evolution theory, paleontologists are forced into all manner of contortions to make all the evidence fit the evolutionary jigsaw. Some experts have accordingly “… offered alternative placements of ausktribosphenidans as a group related to monotremes, peramurid-like eupantotheres or a completely distinct group with convergent “placental-like” features” (Long and others, p. 211). That last comment about convergent placental-like features betrays the wobbliness of evolutionary ideas — Ausk has features that make it look like a placental, but since accepted theory makes that identification embarrassing, evolutionists resort to the old line that in this case shared features may simply come about as a result of evolution producing the same things twice in unrelated creatures, a phenomenon called “parallel evolution” or “convergence”. How wondrous of mutations and natural selection to deal the same card twice!
Australian mammals from the Cainozoic (65 million years ago till the present)
About the same time that the dinosaurs became extinct 65 million years ago, a rift began to develop between Australia and Antarctica as a finger of sea moving in from the west gradually split the two apart, the separation becoming complete between 45 and 38 million years ago. Ever since then, Australia has been drifting north at a rate of about 7 centimeters a year.
Before the drifting began, the northern tip of Australia was situated very roughly where the southern tip of Australia is now. As it moved, the climate changed, creating new and different environments that may have caused the demise of various creatures — in spite of popular ideas about evolution, many creatures simply cannot adapt to even slowly-changing conditions; they flee or perish. For those familiar with the aridity of Australia today it may be hard to believe that for most of the past 65 million years, the continent was well-watered. Dolphin, flamingo (not found in Australia today) and platypus remains have been found around the dried up salt pan known as Lake Eyre in central Australia, attesting to the higher rainfall in the past; so too has pollen from southern beech trees which require much wetter conditions.
The fossil record attests to the passing parade of life forms as new ones better suited to the changed conditions appeared. So far, very little is known about Australian animals for the first 40 million years after the dinosaurs died. In recent years, scraps of teeth and bone have been found in Queensland that prove that various bandicoot and quoll-like creatures lived there between 65 and 25 million years ago, as did a creature very similar to the unique colocolos of South America today. To conclude that not much happened fauna-wise during those years could be a mistake; bear in mind that we are far more ignorant than knowledgeable about the fauna of any given period. The scraps of information we have often give only the broadest outline. Rich assemblages of creatures undoubtedly lived at all times. The closer we come to today the more fossil material is available for providing data; thus, our knowledge of any given period is biased by its proximity or otherwise to our own times.
Animals of the early Cainozoic—65 to 25 million years ago
As already mentioned, until the very end of the twentieth century, about the only extinct Australian mammal suspected to hark back to the first “decades” of the Cainozoic era was Wynyardia bassiana. Sadly for him, he has now been bumped forward in time, and is now placed in the early Miocene, about 25 mya. In the 1980s, serious work was devoted to a fossil-yielding site discovered in the 1930s at Boat Mountain in southeast Queensland. The strata here are dated at about 55 million years old, making the assemblage of creatures found there the oldest known Australian suite of animals. The evidence indicates the area was warm, swampy and forested — a veritable green ark. “In the early Miocene, vast areas of northern Australia were covered in luxurious rainforests. Hoop, kauri and bunya pines tangled with southern beech trees, rarer gum trees and she-oaks. Gigantic fig trees with buttress roots supported curtains of rope-like vines” (Australian Museum 2002, p. 31). Vast areas remained wet and wild until as recently as 50,000 years ago, when gnarled fingers of aridity began spreading.
In those early years of the Cainozoic, Australia formed the most easterly segment of Gondwana (the great southern supercontinent), with Tasmania connecting it to Antarctica and thence to South America. Not surprisingly its creatures, along with other scattered remains of turtles, crocodiles, wading birds and snakes found elsewhere in Australia from roughly the same time, bear some marked resemblance to South American and Antarctic fossil deposits from the same time (Australian Museum, p. 26). However, having said that, another find emphasizes yet again the surprises Creation holds. One of the world's oldest bats has been found at Murgon. No big deal, one may think. Yet mull this over: “No bats of this age are known from Antarctica or South America but close relatives have been found in Europe. Exactly how the Tingamarra Bat arrived in Australia remains a mystery” (Australian Museum, p. 26). Paleontologists would be wise to exercise caution when trying to explain life's history; evolutionary dogma often comes a cropper.
While on this symphony analogy, another point is worth noting. In music, the term “reprise” refers to the return to a theme that had appeared earlier in the symphony. Some evidence suggests that God recreated creatures that had lived then gone extinct. An example; abundant fossil remains of saber-toothed cats in North America give a fairly exhaustive account of their days under the sun. Believe it or not, the fossil record shows that these creatures disappeared totally only to return again later ten times over the course of 40 million years. Paleontologists do find these facts embarrassing, but, so deeply imbued with evolutionary concepts, blandly declare that the cats evolved independently ten times! (Paleoworld, Discovery Channel). The same thing may be true of early Australian creatures.
Back to Murgon; this site contains a number of interesting items, such as the world's oldest song birds, predating overseas finds by 20 or 30 million years! Of great interest, a single tooth was found in 1987 that is unmistakably that of a placental mammal, dubbed Tingamarra porterorum. Oh how significant a find a single tooth can be! (Note that Tingamarra lived 80 to 90 million years after Ausk, so that its discovery does not have relevance for the earlier discussion on placentals and marsupials.) Scientists long thought that when placental and marsupial mammals competed for resources, the placentals always won, and that therefore Australia today is dominated by marsupials as a result of freakish circumstances of the continental drift. Tingamarra has made them rethink this assumption:
Prior to the tooth's discovery, some scientists thought that the “primitive” marsupials that today dominate the Australian fauna had gained the upper hand over “advanced” placental mammals by default… The unexpected discovery of a condylarth [Tingamarra] in Queensland 55 million years ago indicates that marsupials did not inherit Australia by default but by out-competing early placentals (Australian Museum, p. 27).
One marvels at what scientists are able to deduce from a single tooth. They confidently state that Tingamarra was about 8 inches (20 centimeters) long and that it ate insects and fruit. One can be forgiven, however, for taking artists' renderings of what it looked like with a degree of skepticism. No more specimens of this creature have ever been found, suggesting that it had become extinct by the Miocene period, when the record picks up again, this time with fairly diverse fossil finds. Chances are good that if Tingamarra survived into the Miocene, evidence would have been found by now; but nobody can say for sure. Scientists are left puzzling over why placentals vanished from Australia.
Marsupials have surfaced at Murgon, too, including a few mysterious ones, such as Thylacotinga. Scientists can't even decide which marsupial order to place it in. They do note that these teeth vaguely resemble some teeth from both South America and Antarctica that have also been pegged to the early Cainozoic, at which time the three continents were still joined. Tooth size suggests it was about the size of a small rabbit. Equally enigmatic is Djarthia, a mouse-sized insect eater. Like Thylacotinga, Djarthia shares some features with South American marsupials, in this case with opossums. Experts believe that maybe opossums “were once present in Australia?” (Long and others, p. 210).
Also discovered at Murgon are the oldest remains of a kind of marsupial widespread in Australia today — the bandicoot. This 10-inch long bandicoot, roughly the same size as living species, is twice as old as any other identified bandicoot fossils. (Shades of saber-toothed cats?) We could easily pass over this bandicoot without recognizing its significance — it is the oldest-known marsupial of a kind that closely resembles a living line of Australian creatures.
Life's changing parade
The “Tingamarra fauna”, as these remains are collectively known, tells us plainly that a tantalizingly unique suite of animals, and presumably plants, thrived in parts of Australia not long after the dinosaurs perished. One would be foolish to insist that creatures not found at Murgon didn't exist. The lack of koala, kangaroo or diprotodontid remains may be offset by future discoveries. Even if such creatures never lived in Murgon's early-Tertiary steamy forests they may have been hopping and bumping and climbing somewhere else on the huge, flat continent. Whatever the truth, Murgon corroborates the basic thrust of this article — our planet has played host to a huge diversity of creatures that have come and gone in a passing parade of life forms en route to the glorious flora and fauna we are so familiar with. Some modern-day animals had look-alikes 110 million years ago, while others, such as the cuddly-cute numbat, go back in the fossil record no further than two million years.
Other extinct furries appear to have been quite unlike anything we are familiar with today. Riversleigh's “Thingodonta” and “Weirdodonta” (stay tuned) frustrate paleontologists' quests to find a spot to place them in the evolutionary scheme of life.
Animals of the Miocene — 25 to 5 million years ago
Late Oligocene and Miocene rocks have provided considerably more material to work with, especially since 1976, when a site at Riversleigh Station that had been spottily examined once or twice in the early 1900s was “rediscovered” by a team of paleontologists. Realizing the area's potential, many well-rewarded expeditions have been launched; relics of a zoo-full of beasts, including amphibians, reptiles, birds and mammals, have been unearthed in large numbers. To illustrate the richness of the site, before Riversleigh, only two fossilized bat teeth had been found in Australia. While wandering the area that first year, Henk Godthelp stumbled upon a rock “bristling with tiny bones — millions of mouse-sized limb bones” as well as jaws and teeth (Archer and others, p. 23). From two teeth to millions of teeth, jaws and bones in one moment can scarcely be grasped. How many more amazing finds lie ahead, finds which could immensely increase our knowledge?
The discoveries at Riversleigh demonstrate plainly that the wet climate and rainforests we spoke of earlier persisted well into the Miocene. Armed with information from Riversleigh and other Miocene fossil-bearing sites, we are ready for a surface-scratching review of the animals of the epoch. Space constraints mean we must leave out discussion of numerous creatures such as wombats and bandicoots — regrettably.
People around the world are familiar with Australia's cute, tree-dwelling “teddy bear”, the koala, with its big, velvety nose, tufty ears and gentle disposition. As a child I never tired of chancing upon one in a eucalyptus tree on Phillip Island, near Melbourne. But I never dared touch one as we were sternly warned they could turn vicious if annoyed. What would I give to see the 18 extinct species whose remains have been discovered throughout central and north eastern Australia since my first experience with a living teddy. As is often the case, many of these are known only from isolated molars. They ranged in size from Litokoala, about two-thirds the size of the living species, to Phascolarctos which, at double the weight of today's fella, “must have strained the branches of any tree in which it sat” (Long and others, p. 82). In some cases the snout was even shorter than the snout of today's koala while in others it was markedly longer.
“Possum” means different things to different people. In Australia it refers, technically, to tree-dwelling marsupials with short faces and long, prehensile tails and, to make life difficult for ordinary folk, a particular form of dentition that only those trained in teeth minutiae can appreciate. To the average Australian citizen, a possum or cuscus (slow-moving possums with large eyes) is a cat-sized beast that makes strange chesty noises at night, raids rubbish bins and gets into the attic. We are, however, dealing with a highly diverse group of creatures under this rather artificial heading, including at least one species that would sit comfortably on your thumb. About forty four living species spread out over four distinct families are found in Australia, New Guinea and some Pacific islands today. The fossil record has been slow to come along, with few found before the latter decades of the twentieth century. Since then, hundreds of specimens have been found comprising scores of species, the vast majority being new to science. Some, such as Pilkilpildrids, are so different that new families have had to be erected to cater for them.
In many instances the fossil specimens, though considered separate species from living forms, are classified as belonging to modern genera. In other words, they were different from living species, but not by much. Such small change over millions of years may appear to provide grist for the evolutionist's mill. “See”, they say, “just as you would expect”. To the contrary, such tiny changes over the course of 20 million years demonstrate how utterly impossible evolution is. If it took 20 million years to produce barely perceptible differences, how on earth could possums, with their unique suite of characteristics, have arisen from something totally unpossum-like in the mere 40 or so million years provided since the onset of the Cainozoic era? For those who believe in the divine origin of all creatures, the same facts give reason to believe that God did not create each species by divine fiat, but created the “original” possums with a rich genetic reservoir which spilled out over time and in response to environmental conditions into the numerous variants we call species. The Bible does not tell us that each species, as biologists define them, was separately created.
Another family that had to be erected to handle extinct species is the family Ektopodontidae. When the first isolated teeth of Ektopodon were unearthed in northern South Australia in 1962 they caused quite a flurry. They were considered so unusual that a new terminology had to be devised to describe them! At first Ektopodon was declared to not be a marsupial; later collection of teeth and a jaw firmly established its marsupial inclinations. Let Archer describe the discovery:
When the first ektopodontid molar turned up… Reuben Stirton, Dick Tedford and Mike Woodburne were utterly confused… Their field notes for that day read like a table-tennis ball, bouncing from one mad idea to another!… Soon they found themselves in a corner. Having eliminated all other possibilities they concluded that its high coefficient of weirdity made it a candidate for the oldest and first known Miocene monotreme (p. 132).
They were wrong. A discovery of a complete lower jaw years later, together with new interpretations of the tooth structure, has convinced those who decide these things that it is closer to Phalangerid possums than to anything else. But the strangeness of the teeth is still puzzling. The best the experts can do is to liken Ektopodon to a cuscus, a possum-like creature with squirrel-like features. Its large eyes suggest it was nocturnal in habit. Their forward-directed configuration implies it had good stereoscopic vision, making it likely that it either lived in trees or was a hunter or both. Its teeth, as mentioned earlier, suggest it ate hard seeds and nuts; maybe it occupied a squirrel-like niche. A tree-dwelling, hunting, squirrel-like, cuscus-like animal sounds peculiar indeed. All in all, Ektopodon remains quite an enigma.
Since the first discovery, about seven species have been found in South Australia, Victoria and Queensland which have been divvied up among four genera. Ektopodontids barely survived into the Pleistocene, and then vanished completely.
Everybody on this planet would recognize a 'roo or wallaby when they saw one and would know that these creatures take huge leaps through the action of powerful spring-like hind legs. Based on principles of taxonomy, experts like to lump them together with tree-dwelling possums, treating them as “specialized possums”. Hmm. Kangaroos are placed in the superfamily Macropodoidea, which contains between sixty and seventy living species, all of which are gentlemen herbivores. The fossil record has so far revealed about 100 different species of extinct kangaroo and rat-kangaroo from Australia and New Guinea divvied up among about 30 extinct genera and a handful of living genera. About 30 species are so far known to have lived during the Oligo-Miocene, 40 in the Pliocene and another 40 during the Pleistocene. As many other creatures have done throughout time, some roos, such as Troposodon, took no notice of opinions of future paleontologists about prehistoric eras, and dared to cross the boundary between epochs.
One fundamental difference between early kangaroos and modern kangaroos warrants mention. Modern Australia is largely arid with vast tracts of woodland and grassland and few rainforests; most modern kangaroos carry teeth and jaws that “have a special design to help them feed on the tough, siliceous grass stems” (Vickers-Rich and others 1996, p. 111). Before these grasslands laid siege to and battered down the walls of the ancient rainforests, most roos had a very different jaw and tooth anatomy; they were browsers that eschewed tough grass and dined on tender tree salads. (A number of them lived among the branches.) The entire gut must have been designed to deal with leaves rather than grass. No matter how many millions of years you allow, you just can't get from leaf-chomping teeth and jaws to grass-chewing versions through a series of tiny, accumulating, random changes. Scientists acknowledge that, “none of these modern lineages have a generic pedigree that extends any further back than 4.5 million years” (Archer and others, p. 117). All of a sudden, there they were!
Unlike today's roos, some of the ancient ones were meat eaters, although so far only one seems to have been a true carnivore, the others being opportunistic “eat-alls”. This carnivorous denizen of Riversleigh's early forests cannot but help capture one's imagination. Dubbed "Fangaroo" (Ekaltadeta ima), he came equipped with a set of dagger-like canines, certainly making him look the part of a savage carnivorous killer. However, though he no doubt ate meat, he was probably a scavenger rather than a killer, using his sharp pegs for display rather than as weapons, according to the experts. This “feisty bit of unpleasantness” grew to about five feet tall (1.5 meters). Its skull was found in the imaginatively-named “Camel Sputum” rock.
Marsupial lions: carnivorous herbivores
Over a century passed after the discovery of the first marsupial lion fossil (Thylacoleo carnifex) at Lake Colongulac in Victoria in 1852 (see below at “Lion King”) before any more skeletal material was found. Since 1974 bones and teeth of at least five different species from two other genera have been found in South Australia, Northern Territory and Queensland. One was probably no larger than a house cat, while the Lion King got up to 215 pounds (100 kg).
Evolutionists are embarrassed by marsupial lions. Their “nearest relatives” are gentle, rear-pouched, grass- and leaf-eating marsupials such as pig-like wombats and cuddly koalas. Many paleontologists for many years rejected the obvious evidence of the teeth — marsupial lions dreamed of joints of wallaby and crunchy bones, not of flummery and green salads. One paleontologist suggested they ate melons! Though their tooth structure carries echoes of herbivorous koalas, wombats and kangaroos, other features, such as the long slicing premolar, are radically different.
“Lions” ain't “tigers”
In spite of the similarity in name, a strict distinction needs to be made between Thylacoleo, on the one hand, and Thylacinus, on the other. The latter is a carnivore through and through, with no similarity in tooth structure to marsupial lions. The “living” representative of the group, the dog-sized, striped Tasmanian “tiger”, is now presumed extinct by most experts. Since, as a general rule, each carnivore needs a supply of at least ten victims, early Thylacinid remains are relatively rare. Nevertheless, at least half a dozen mono-generic species have been recorded going back about 25 to 30 million years. Experts believe that Thylacinids were marathon runners; rather than outrun their prey, they just followed its scent until the victim dropped to its knees from exhaustion.
We have already been introduced to Wynyardia. For many decades Wynyardia bassiana stood a lonely vigil on the Wynyardiid fossil shelf. However, in 1983, when the Riversleigh Godthelp Hill site was discovered, “wynyardiids were suddenly everywhere”, representing either two or five species (Archer and others, p. 109). Further Wynyardiid discoveries from Tasmania in the south suggest these creatures occupied a very wide range.
For many years experts held to the view that Wynyardia was similar to, if not identical with, modern brush-tailed possums, but about the size of a dog. Since the teeth were all worn away as the fossil-bearing rock, with Wynyardia's skull protruding, slid slowly down the bluff onto the beach, a vital key was missing. Studies in the 60s and 70s of the ear region and brain cavity, however, have convinced paleontologists that it is unique — similar to modern possums, but also significantly different. More importantly, finds of similar skulls with teeth intact from the Lake Frome Basin have emphasized the differences between Wynyardia and modern possums inasmuch as the teeth are more like those of a kangaroo, wombat or even koala.
A number of remains have been discovered that just don't fit into any established groups of animals; we'll mention just a couple. One of the most puzzling is known affectionately as “Thingodonta”. Its dentition is so different from any other marsupials that a new order was erected for it — Yalkaparidontia. (Only four other orders of marsupial are recognized.) The weird structure of the teeth — closer to a Madagascan Tenrec than to any other living creature — has led to many hours of blissful speculation as to what it ate, what it looked like, and how it lived. Tooth structure suggests that it lived on something that had a tough skin (they had teeth for puncturing) but soft insides. Earthworms, maybe?
Then you have “Weirdodonta”, revealed by a single tooth unearthed at Riversleigh in the late 80s that bears anatomical features utterly unfamiliar to “toothologists”. Since Weirdodonta sounds a little unprofessional, paleontologists decided upon a name with a more scientific ring — Yingabalanara richardsoni. I kid you not. Though the experts can say with some confidence that it was about the size of a mouse, after that the going really gets tough: “What this animal looked like is anybody's guess” (Long and others, p. 214).
And then you have the diprotodontids, lumbering Miocene “relatives” of wombats and koalas that may have competed with kangaroos for grass and low shrubbery, outnumbering them in numbers both of individuals and of species. Ranging in size from small sheep to large hippos, these creatures almost dominated the continent for the entire Miocene, the last and largest of its kind, Diprotodon optatum, living until just thousands of years ago. One species, Neohelos tirarensis, “may have been as common and widespread in the Miocene habitats of Australia as cattle are today” (Archer and others, p. 111). They were characterized by small brains and a big appetite for soft leaves, stems and grasses. (One group of diprotodontids — Palorchestids — appears to have been able to deal with harder, more abrasive grasses.) Some evidence suggests that the threat of predation by marsupial lions, thylacines and giant pythons saw them traveling in large herds. Some appear to have loved wallowing in water.
Bizarre names such as Bematheriusm, Kolopsis, Euryzygoma, Palorchestes, Ngapakaldia and Zygomaturus capture the essence of the bizarreness of these creatures, of which roughly 50 species are known from all parts of Miocene Australia, including Tasmania.
Animals of the Pliocene (5 to 2 million years ago)
Many of the creatures described above in the section on Miocene creatures survived into the Pliocene. However, remains have been found of numerous creatures that appear to be unique to this epoch. Remember, the parade keeps passing. A chief source of Pliocene fossils in Australia is Bluff Downs in northern Queensland. Fossils there are buried under meters of volcanic basalt, providing feldspars for radiometric dating.
One magnificent beast from this period is Euryzygoma, a diprotodontoid. This cow-sized creature lived in a wide range of habitats, from wetlands to dry forest and scrubland. “Eury” skulls have a feature that has long intrigued paleontologists — it has large flaring cheekbones which undoubtedly gave it a stuffed-chipmunk-cheek look. Speculation as to the purpose of this feature ranges from food storage, to resonating chamber for amplifying its voice, to sexual display.
Far and away the most intriguing animal to come from this period is the horse-sized diprotodontid Palorchestes azael, one of the most unusual mammals ever to have lived. When first discovered in Victoria in 1874 it was described as a kangaroo; reconstructions suggest, however, that this beast hardly looked roo-like. With only teeth and jaws to work with, it's not surprising that early investigators got it wrong. In 1958, Jack Woods of the Queensland Museum argued from details of its jawbone structure that it was not a kangaroo at all, but rather a diprotodontid. More remains have become available in recent years, including an entire skeleton found in 1980 gathering dust in a museum, giving researchers a good picture of their structure.
The relative rarity of their remains suggests they were solitary creatures. It might also infer that they had low rates of reproduction and occupied large home ranges (Rich and others, p. 236). The structure of the massive forearm is most intriguing, with the upper and lower bones being locked permanently together in a slightly flexed position, thus giving great strength to the forearm. Together with the presence of claws similar to but much bigger than those of a koala, this structure suggests that Palorchestes was very adept at ripping and tearing the bark and wood of trees. In addition, the tongue was elongate and narrow, as in giraffes where it is used for reaching into trees for food. The teeth suggest that fibrous or abrasive foods were eaten. Probably this beast was a tree-ripping leaf eater.
Two special features of its skull — highly-retracted nasal bones and enlarged holes for the arteries that served the "nose" area — provide very strong evidence that it came decked out with a trunk. Another intriguing suggestion that comes from the structure of the legs and claws is that Palorchestes may have even climbed vertically or upside-down in a sloth-like manner. In sum, a truly bizarre creature.
Animals of the Pleistocene (2 million years to present)
Bizarreness does not end with proximity to our time. In fact the Pleistocene epoch vies with any other for its fascinating bestiary. For example, whereas today only two or three species of wombat survive, during the Pleistocene “there were many more, ranging from tiny kinds the size of small dogs to the cow-sized Phascolonus gigas with massive chisel-like upper incisors” (Archer and others, p. 107). Unlike today's wombats, their teeth did not grow throughout life.
The best-known diprotodontid of all times is the widespread, water-loving Pleistocene Diprotodon optatum, the first fossil mammal in Australia to be given a name. These large, pouched mammals may have survived until only 20,000 years ago (Macdonald 1985, p. 824). At least one skeleton of Diprotodon has nicks on its bones suggestive of having been butchered by hunters' knives.
Roughly the size of a cow with the shape of a wombat, Diprotodon had some unusual features, not least of which were its feet, for few other mammals have feet remotely like them (Rich and others p. 241). The toes were reduced to stubs, the weight having been borne primarily by the wrist and ankle bones. Their gait was probably rather unusual as a result. The man who named Diprotodon in 1838, the famous British paleontologist, Sir Richard Owen, sought in vain for years to get hold of the bones that would reveal the structure of Diprotodon's feet. In his final work on the subject, he had his artist depict Diprotodon standing in grass to cover the feet. In a classic irony of life, Owen died in the very year — 1892 — when an aborigine from Callabonna, South Australia, hearing about elephants at a local circus, told some local folk that he knew where lots of elephant bones could be found. The offer of a £1,000 reward for a skeleton led to some comical cloak and dagger stuff with various people claiming the discovery, the resulting confusion being so great that nobody got the reward.
Diprotodon's uniqueness is most apparent in its skull, which is surprisingly delicate. Much of the skull bone is only a millimeter thick, much thinner than one would expect by comparison with other mammals. Also, the brain case consisted of a box-within-a-box. The brain was in the inner box, which was separated from the outer one by air chambers supported from being crushed by delicate sheets of bone connecting the two.
Diprotodon came into being as Australia was drying out; its diet and lifestyle enabled it to survive fairly harsh conditions. Its remains have been found in areas known to have been fairly arid at the time. None have been found in Tasmania, for instance, which was wetter. Paradoxically, though they lived in arid regions, their remains are usually found not far from where water would have stood, suggesting they didn't stray far from water.
At about double the size of the living Red Kangaroo, the largest extinct kangaroo known, Procoptodon goliah, or Short-faced Kangaroo, lived towards the very end of prehistory. Weighing in at over 400 pounds (200 kg) and reaching almost 10 feet (3 meters) in height, this monster may have survived until about 40,000 years ago. Armed with grappling hooks where other self-respecting kangaroos have paws, strange-shaped hands, and with a shortened face with forward-pointing eyes that made it look as if it had crashed into a wall at full hop, Procoptodon ranks as one of the strangest of roos. The evidence suggests it ate both grass and leaves with equal relish.
The lion king
One of the better known creatures is Thylacoleo carnifex or, more colorfully, the marsupial lion, but perhaps more appropriately “the bush terror”. Thylacoleo seems to have been a strange mix. Early scientists variously likened it to a rat kangaroo, kangaroo, possum or koala (its nose was of the soft and cute kind). But the give-away as to the true nature of Thylacoleo is its large incisors and slicing premolars, which were designed for "piercing, holding and lacerating, like the canine of a carnivore” (Rich and others, p. 225). This feature made the marsupial lion truly the odd man out in the marsupial troupe. As Norman so colorfully put it:
The marsupial lion was powerfully built and had exceptionally large incisor teeth, which it must have used instead of the more usual canines for stabbing, and very long, blade-like cheek teeth for slicing up the flesh of its victims (1994, p. 187).
Studies in 2005 showed that its bite was twice as powerful as that of a hyena, and that it was double the size previously thought. Thylacoleo may have died out as recently as thirty thousand years ago (Macdonald, p. 824). If you had been born a little sooner you may have had to think twice about camping out.
There were giants on the earth in those days
If you have ever visited a big museum anywhere in the world, undoubtedly one of the things that has lodged in your memory is images of creatures similar to today's, but that come in much bigger packages. During the Pleistocene, animals that had been small became big, big beasts became huge and huge creatures became enormous. Megafauna, as they are known, are not restricted to Australia. For instance, until only about 10,000 years ago, giant armadillos weighing in at an estimated 500 pounds (230 kg) and stretching over two meters long ranged the American South (Discover April 1998, p. 14). Europe had its huge cave lions, cave bears, and woolly mammoths. Africa's megafauna — elephants, giraffes, and rhinoceroses — survive to this day.
Australian giants included echidnas, rat kangaroos, kangaroos and wombats, but not giant platypus, possum or koala. Various theories have been proposed for the phenomenon of gigantism; scientists believe that it was in some way connected with a worldwide trend towards a drying and cooling climate. However, even if one accepts the possibility that built-in genetic richness would have allowed creatures to change size in response to climate, this theory seems unsatisfactory in light of the general consensus among earth historians that the climate at this time experienced dramatic cyclical reversals of climate, swinging between cold and dry and wet and warm over the course of tens of thousands of years.
We may never know exactly how God brought about this unique era of megafauna. But doesn't it thrill you to contemplate giant sloths, armadillos, beavers, turtles and kangaroos? Don't you feel inspired by the thought that this planet has played host to throngs of creatures long-since gone the way of all flesh? If only we could turn the story of life into a musical extravaganza, we would never get tired of listening to its brilliant interplay of novel elements and repeated themes, all perfectly harmonized for maximum pleasure. To God be the glory!
References and notes
1 Million years ago
Archer, M., Hand, S. J., and Godthelp, H. 1991 (reprinted 2000), Australia's Lost World: Prehistoric Animals of Riversleigh, Reed New Holland
Australian Museum (with preface by Michael Archer) 2002, The Evolution of Australia: 110 Million Years of Change, Sydney
Dawson, T. J. August 1977, Kangaroos, Scientific American
Gould, S. J. 1980, The Panda's Thumb, Penguin Books, London
Long, J., Archer, M., Flannery, T., and Hand, S. 2002, Prehistoric Mammals of Australia and New Guinea, The John Hopkins University Press, Baltimore and London
Macdonald, Dr. D., editor 1985, The Encyclopaedia of Mammals, Facts on File, Inc., New York
Norman, D. Dr. 1994, Prehistoric Life: The Rise of the Vertebrates, Boxtree, London
Quirk, S., and Archer, M. 1983, Prehistoric Animals of Australia, Australian Museum, Sydney
Rich, P. V., van Tets, G. F., and Knight, Frank 1985, Kadimakara: Extinct Vertebrates of Australia, Pioneer Design Studio, Lilydale, Victoria
Vickers-Rich, P., Rich, L. S. and Rich, T. H. 1996, Australia's Lost World: A History of Australia's Backboned Animals, Kangaroo Press, Kenthurst, NSW
Vickers-Rich, P., Rich, T.H. 1993, Wildlife of Gondwana, Reed, Chatswood
Wroe, S. 1998, A new ‘bone-cracking' dasyurid from the Miocene of Riversleigh, northwestern Queensland, Alcheringa, 22:277-284
Dawn to Dusk publications
Other printed material
On the Web
For some interesting new insights into Thylacoleo carnifex, see "All the better to bite you with"
All the books mentioned in the References section are worth reading, particularly the one by Archer, Hand and Godthelp
Colbert, Morales & Minkoff, Colbert's Evolution of the Vertebrates: A History of the Backboned Animals Through Time
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