Over millions of years Victoria has moved from the tropics to the Antarctic circle and now to the temperate zone. It has been shaped by periods of volcanic activity and major climate shifts.
Over millions of years Victoria has moved from the tropics to the Antarctic circle and now to the temperate zone. It has been shaped by periods of volcanic activity and major climate shifts.
This website provides more information about some of the featured exhibits in 600 Million Years: Victoria evolves. Explore the geological time scale and and learn more about the plants, animals and environments of Victoria over the last 600 million years.
600 Million Years: Victoria evolves is now showing in the Science and Life Gallery at Melbourne Museum. Visit What's On for more events at Melbourne Museum.
Lifeless land, teeming ocean
542 million years ago the fossil record shows a dramatic expansion of animal life in the sea, known as the ‘Cambrian explosion’. The body plans of some animals that evolved at this time show an ancestry to modern animals. There were also some weird and wonderful creatures unlike any alive today. The ocean teemed with worms, jellyfish, trilobites and brachiopods.
The ‘explosion’ appears in part because some animals had evolved tough body parts, such as shells or exoskeletons, which are more readily preserved as fossils. This reflects a change in the ecology as predators evolved, fuelling the need for defensive features such as spines and hard shells; the predator/prey arms race had begun. One of the most successful hard-bodied groups – the trilobites – first appeared in the Cambrian.
At this time, what we now call Victoria did not exist as land. The edge of the continent was in the west (in present-day South Australia). Offshore volcanoes erupted lava onto the ocean floor and built up chains of volcanic islands. Sand and mud washed off the barren dry land and accumulated in the ocean between the continent and the volcanoes, forming sedimentary rocks. Over millions of years these rocks were compressed, heated and thrust upwards along giant faults. Today they form the bedrock of western Victoria and the remains of these ancient volcanic rocks are called ‘greenstones’.
Highly detailed fossils such as this Redlichia trilobite have been found at Emu Bay, on Kangaroo Island in South Australia. Other fossils found here include soft-bodied and thin-shelled animals such as worms, crustaceans, and the large predator Anomalocaris. This site provides a snapshot of life in the Cambrian Period – the best record in the Southern Hemisphere.
Early trilobites were among the first arthropods and had quite distinctive body forms. Over the next 100 million years, trilobites evolved into a variety of different body forms and sizes.
Archaeocyathids were important reef-building animals, but they were not the first reef-builders.The earliest reefs consisted of stromatolites – structures that build up over thousands of years when marine bacteria trap sediment. Stromatolites became much less common when grazing animals such as snails evolved in the early Cambrian.
In the Cambrian, another type of reef-building organism appeared – sponge-like organisms called archaeocyathids, meaning ‘ancient cups’. Their hard bodies formed the distinctive patterns seen in limestone from this time. Fossils of archaeocyathids show that they built up reef structures by growing on top of the skeletons of dead archaeocyathids, and in doing so created reef environments that were important habitats for other marine life.
The Burgess Shale of British Columbia in Canada is a rich source of fossils that help us understand life in the Cambrian Period. The fine-grained rock has preserved details of many types of extinct marine animals, including soft-bodied and thin-shelled forms that are not commonly fossilised.
Larger animals with a hard exoskeleton have also been found here, and one of these is Anomalocaris, the top predator of its time. Fossils of Anomalocaris and its relatives have been found in China, North America and in South Australia.
Wiwaxia is another animal with uncertain affinities; some palaeontologists think it should be placed with the molluscs, others think it belongs with the worms and still others say it was unlike either of these and has no known relatives. Its back was covered in hard plates called sclerites with two rows of long spikes, while its underside was probably soft. It is thought to have fed using rasping teeth for scraping food off the sea floor.
Greenstones are ancient rocks formed from lavas erupted by underwater volcanoes. Over hundreds of millions of years the rocks were buried and compressed during massive earth movements that built Victoria’s geological foundations. Minerals that formed when the rocks were buried are often dark green, so geologists call them ‘greenstones’. The history of the rocks can be traced by studying these minerals and their textures.
The higher temperature and pressure exerted on the buried volcanic rocks changed their mineral composition – a process called metamorphism. Super-hot fluids moved through fractures and pores in the rocks, carrying dissolved elements such as calcium, iron, aluminium and boron. When the fluids cooled, minerals such as garnet and axinite crystallised in open spaces in the rocks.
These rocks are among the oldest in Victoria. They began as sediments deposited on the ocean floor. Then they were buried and compressed to form sandstone and mudstone, before being uplifted during periods of mountain-building. Slate and schist formed in regions of higher pressure, and gneiss and granite were formed where the temperatures were hot enough to partly melt the rock. This process is called metamorphosis.
During the Ordovician period, a diversity of life filled the seas – cephalopods, trilobites, reef-building invertebrates and graptolites. However algae were the only multicellular plants and there was still no complex life on land.
This period is sometimes known as ‘the age of graptolites’ but it’s also importantly the era in which jawless fishes – the first vertebrates – appeared.
A mass extinction event marked the end of the Ordovician, in which more than half of all marine invertebrate species went extinct. This extinction particularly affected the trilobites, with heavy losses of shallow-water species.
Offshore along the coastline of ancient Australia there were large faults extending to the Earth’s mantle. These allowed magma (molten rock) to erupt onto the sea floor, where it cooled and hardened in the water. In this way underwater volcanoes formed and grew into chains of islands.
Today, the ocean trenches and chains of volcanic islands that we see around the western margin of the Pacific Ocean formed in exactly the same way as the ancient features.
Graptolites were marine animals that formed twig-like or net-like colonies containing many individual microscopic individuals. The colonies mostly floated in the oceans, but some were attached to the sea floor.
Because they were abundant, they fossilised well, and various shapes evolved over time, graptolites are an important group of fossils used as markers to date rocks of Ordovician to early Devonian age. Those found in marine sedimentary rocks from the Ordovician in Victoria are of world-wide significance.
Arandaspis was one of the first fishes, although it was very different to modern fishes. It did not have jaws or paired fins, and its body was protected by armour plates and scale-like ‘scutes’. Unlike its tough outer skeleton, the internal backbone of early vertebrates like Arandaspis was probably made of cartilage.
In some areas, Cambrian and Ordovician sedimentary rocks contain large concentrations of elements such as phosphorus, barium and sulphur. The phosphorus came from dead animals that were buried in the sediments on the ocean floor. Long after the sediments were folded and uplifted, rock weathering released the phosphorus to form minerals such as wavellite and turquoise. Barite crystals also formed during rock weathering.
Trilobites were at their zenith at the start of the Ordovician with over 60 different families living in a variety of marine environments. The morphological diversity of this group peaked during the Ordovician too – they came in a wide variety of shapes and sizes, and some became powerful swimmers. Neoasaphus probably had good vision thanks to its stalked compound eyes.
After this phase of rapid evolution, the mighty trilobites began to decline, becoming rare by the Carboniferous before complete extinction at the end of the Permian.
Crinoids, or ‘sea lilies’, are echinoderms related to sea urchins and sea stars. They appeared in the Cambrian and were one of the most abundant animals in Palaeozoic seas.
Crinoids have cup-shaped bodies with many flexible arms, often lined with tentacle-like pinnules used to gather food. Most early crinoids used a long stem for attachment, but most forms living today are stemless.
The land turns green
Until plants evolved, the landscape was barren. Without plants to stabilise the soil, the Earth was bare and scoured by erosion. A green fringe on the water’s edge began a slow transformation; a small number of plants developed a revolutionary adaptation – vascularity, or the ability to transport water and nutrients through a network of specialised tissue.
These early vascular plants were the first to grow on land, and Baragwanathia, from Victoria, was one of the first leaf-bearing plants known. Land plants, although very low-growing, provided shade, shelter and food, inviting invertebrates to follow into a new world of opportunity.
In the oceans, corals formed expansive reefs while sea-lilies and trilobites thrived. The first jawed fish evolved, and became active predators as well as being prey for other animals. Sea-scorpions and cephalopods were the largest predators in the seas, and some sea-scorpions even ventured onto land.
Australia was part of the supercontinent Gondwana, near the equator with a warm climate. ‘Victoria’ continued to be formed by sedimentation, mountain building and volcanism. Near the end of the Silurian Period, intense heating of the crust beneath Victoria ‘sweated’ gold from deeply buried volcanic rocks into super-hot salty water. This water moved upwards until, near the surface, the gold crystallised out with quartz. This process continued at intervals for another 100 million years, making Victoria one of the world’s richest gold provinces.
The Victorian fossil plant Baragwanathia marked the first emergence of the club mosses, and was very important in the evolution of land plants. It was one of the first leaf-bearing vascular plants, which means it had strong internal tubes for transporting water, nutrients and gases. It was more advanced than any other land plants, and was a giant of its time – but only the size of a small shrub. From these modest beginnings, the club mosses evolved into tree-sized plants that dominated forests during the Devonian.
Club mosses survive to this day; the Rock Tassel-fern from northern Queensland is similar to Baragwanathia from 415 million years ago. The Rock Tassel-fern is an epiphyte on rocks, particularly near waterfalls, and on tree trunks.
The oceans were home to a new type of predator – fast-swimming, jet-propelled molluscs called cephalopods, with keen senses and a cluster of grasping tentacles. The first cephalopods like Endoceras had cone-shaped shells. Later cephalopods had shells that were coiled or became enclosed within the body. This last group were the ancestors of modern squids, cuttlefishes and octopuses.
Eurypterids, or sea scorpions, were a group of arthropods whose closest modern relatives are horseshoe crabs. They were fierce predators that lived in the ocean, estuaries or rivers. The eurypterids that ventured out of the water were among the first animals to walk on land. Some eurypterids were enormous – the biggest was over two metres long.
During the Silurian, Crinoids were very abundant and many different species are preserved in limestone deposits worldwide. They sometimes lived in large accumulations known as ‘crinoid gardens’. Some crinoids grew stems up to 30 metres long. When the animals died, ocean currents often broke up the remains and rolled them together in vast amounts to form thick deposits of limestone. In Victoria, crinoidal limestones are found in the Lilydale, Kinglake and Buchan districts.
These arthropods lived in water but also ventured onto wet sand flats, perhaps to find food. They left some of the first animal tracks on land, now preserved in fossils near Kalbarri, Western Australia. Kalbarria’s tough outer coat gave it some protection from drying out when it was out of the water.
Vertebrates venture on to land
Life on land became more complex as plants developed, insects diversified and one group of fish developed sturdy fins, eventually giving rise to limbs. These were the early tetrapods – the first backboned animals to walk on land. From these first land vertebrates, groups evolved that could roam further from the water.
In shallow seas, reef-forming corals were widespread and shared their environment with forests of sea-lilies and sponges. An array of fishes swam in the oceans, rivers and lakes – armoured placoderms, sharks, ray-finned and lobe-finned fish of all sizes and habits give the Devonian the nickname “The Age of Fishes”. They shared the waters with ferocious predators like sea scorpions and cephalopods. Towards the end of the Devonian, a major extinction event severely affected warm-water marine life, but had a lesser effect on terrestrial life.
Australia was part of the supercontinent Gondwana, near the equator with a warm climate. Volcanoes exploded across central and eastern Victoria late in the Devonian Period. The most spectacular formed when vast blocks of the crust collapsed along faults. Massive turbulent clouds of hot gas, crystals and pumice spewed from the fractures and flowed into the cauldrons and rift valleys. These were amongst the largest volcanoes ever seen in Earth’s history. Mt Macedon and the Dandenongs are remnants of these eruptions.
Immense volcanoes exploded across Victoria during the Devonian. Calderas, or craters, many kilometres across were filled with thick layers of hot ash and pumice. Local plants and animals were wiped out, and gigantic clouds of dust and gas probably affected the Earth’s atmosphere. These volcanoes remain in the Victorian landscape as plateaus and mountains since their hard rock resisted erosion.
A barrier reef teeming with life existed 375 million years ago in what is now the Kimberly region in Western Australia. The warm sea was home to a diversity of molluscs, crustaceans, sea scorpions and fish. The fish fossils found near Gogo include armoured placoderms, spiny acanthodians, sharks, ray-finned fish and lobe-finned fish such as lungfish preserved in fine detail.
One of the best preserved fossils from Gogo is a lobe-finned fish called Gogonasus. The fossil skull and pectoral fins of this fish show some interesting features that provide clues to the origins of land vertebrates. Although clearly still a fish, the skull shows primitive structures that would became important features for related air-breathing tetrapods.
Tiktaalik is sometimes called a ‘fishapod’; it was an intermediate form between fish and tetrapods. The wrist bones in the front fins were more developed than in earlier lobe-finned fish, and the fins had strong rays, suggesting that they may have been used to prop up the animal’s body under water.
Acanthostega was one of the first tetrapods. It had legs rather than fins, ending in fingers and toes, but was still an aquatic animal that could not walk on land. Acanthostega probably lived in shallow, plant-choked swamps, ambushing prey near the water's edge.
An early tetrapod similar to Acanthostega waded through shallow water over 360 million years ago, leaving fossilised footprints with clear toe impressions. This trackway was discovered near the Genoa River in eastern Victoria.
Dicranurus was a trilobite that lived in a shallow sea located near Morocco during the Devonian. Dicranurus was covered in pairs of ornate and formidable curved spines, which may have been used as a defence against an ever-increasing number of predators.
A major extinction event at the end of the Ordovician period had a great impact on trilobites and other shallow marine animals. Trilobites recovered somewhat during the Silurian but never again reached the same diversity that they once had. In another series of extinctions in the second half of the Devonian, all but one of the remaining major groups of trilobites disappeared.
Ptenoceras was a nautiloid, a cephalopod related to modern-day nautiluses. The shell of Ptenoceras was loosely coiled, unlike the straight, conical shells of earlier nautiloids.
Ptenoceras is also one of the few extinct cephalopods where fossils have preserved clues about the markings on the shell; an examination of some fossilised Ptenoceras shells show that they had dark, banded markings on a pale background, similar to the markings seen on the shells of modern-day Nautilus.
Giant insects and early reptiles
Land plants were developing strong root systems that allowed them to grow larger and occupy drier land. Trees were growing taller, and beneath their canopy new environments began to evolve. The copious plant life was literally changing the atmosphere, as the abundant trees pumped more oxygen into the air. These swampy forests were preserved as major coal beds in Europe and North America, giving the Carboniferous Period its name. While giant millipedes lived on the forest floor and giant insects took to the air, amphibious tetrapods became diverse – some became more adapted to spending more time on land, while others returned to the water. From the tetrapods evolved another group of land vertebrates – the early reptiles.
Australia, as part of Gondwana, drifted on its tectonic plate from near the equator to near the south pole, gradually becoming colder. Unlike the forests forming coal in other parts of the world, the vegetation was more slow-growing and adapted to a cool climate. The fossils show a transition from giant club-mosses to seed ferns. There are few fossils from Victoria at this time to give clues to the life on land.
(meg-a-new-ra and are-thro-ploo-ra)
The Carboniferous was a time of giant land invertebrates, and Arthropleura, a gigantic relative of millipedes and centipedes, was the largest of them all. In spite of its fearsome appearance, it was probably a plant-eater but may have occasionally eaten small vertebrates and insects.
Flying above, the massive dragonfly Meganeura hunted insects and other small animals on the wing. The moist, oxygen-rich atmosphere of the Carboniferous made respiration easier for insects, allowing them to grow very large, and Meganeura was one of the largest flying insects.
Pederpes was a more advanced early tetrapod than the Devonian Acanthostega. Its jointed legs had forward-pointing toes, so it could walk better on land. But its hearing was better suited to underwater environments. It probably spent a lot time in the water and may have hunted there.
Goniatites was an ammonite; a cephalopod with a distinctive round, coiled shell. Goniatites and related ammonites were abundant in the oceans of the Carboniferous, but were relatively small. The distinctive zig-zag markings on the fossil indicate the internal chambers of the shell.
Pentremites was a blastoid; a type of echinoderm related to the crinoids or ‘sea lilies’. Like crinoids, these animals lived on the sea floor attached by a stalk, and collected food that floated in the currents by trapping it in tentacle-like structures called branchioles. Blastoids were common in the Carboniferous, but became entirely extinct by the end of the Permian.
This odd-looking shark lived in shallow coastal waters 350 million years ago, feeding on fish, cephalopods and crustaceans. The purpose of the strangely-shaped fin and spiked forehead of Stethacanthus is uncertain – they may have played a role in courtship or as a visual threat.
Deserts and ice shape life and landscapes
During the Permian, the landmasses merged, forming a ‘supercontinent’ called Pangea. The remainder of the Earth’s surface comprised a single ocean. Polar ice caps covered the southern (Gondwanan) part of Pangea, while desert areas covered the northern inland part of the continent.
Land animals such as amphibious tetrapods and reptiles lived in the zones where plant life thrived. The oceans teemed with fish and invertebrates until the end of the Permian, when the biggest natural disaster in history killed 90 per cent of the planet’s species. The cause is not yet known – perhaps an asteroid impact, stagnant oceans, massive volcanic eruptions, a significant fall in sea levels, or a combination of these. Many marine groups became extinct including tabulate and rugose corals, eurypterids and the trilobites.
The ‘great dying’ also had an impact on life on land. The extinction of many plants reduced the food supply for large plant-eating reptiles and removed habitat for insects. The ancestors of mammals, dinosaurs and the reptiles we see today survived in small numbers.
Australia lay beneath an ice cap at the start of the Permian and Victoria was swathed in a slow-moving ice-sheet. As the ice retreated, forests developed with Glossopteris (seed ferns), tree-ferns, club-mosses and horsetails. As the climate became drier, plants such as conifers, cycads and ginkgos evolved. Amphibious tetrapods, reptiles and a great variety of insects inhabited these forests.
By the Carboniferous only one major group of trilobites called proetids still survived, and they were generally very small. From the mid-Carboniferous until the end of the Permian, trilobites continued to decline, becoming very rare towards the end of the Permian. They went extinct entirely, along with many other marine animals, at the end of the Permian 250 million years ago.
Palaeodictyopterids were insects related to dragonflies and mayflies. They first appeared in the Early Carboniferous, and became diverse and abundant until their extinction at the end of the Permian. They had elongated, sharp mouthparts for piercing and sucking plant tissue. As well as their large wings, they had a pair of ‘paranota’ or winglets, which didn’t function as wings during flight.
This fierce-looking, mammal-like reptile was an active, sharp-toothed predator. Although the skull in the exhibition is 40 cm long, this is only from a juvenile Eotitanosuchus – adult skulls were nearly one metre long, making their total body length more than five metres.
Paralegoceras was an ammonoid – this group of cephalopods possessed coiled shells and were probably active predators or scavengers. Ammonoids almost died out in the Permian extinction but managed to recover and persist until the end of the Cretaceous period. As a group, cephalopods survived the Permian extinction and nautiluses, octopuses and squids still live in the oceans today. However the number and diversity of cephalopods were much reduced by the Permian extinction event.
Jimbacrinus had five arms which were lined with fine tentacle-like structures called pinnules. Like all crinoids, it used these unfurled arms to feed on small animals and particles in the water.
Fossils of Jimbacrinus show that they were abundant seafloor animals in what is now Western Australia during the Permian.
Although the fossil of Helicoprion looks like a shell, this spiral-shaped structure is a ‘whorl’ of teeth from a shark unlike any shark alive today. This tooth whorl formed part of the lower jaw and probably helped grasp prey. Helicoprion grew to nearly three metres. This type of shark survived the Permian extinction.
Even after 290 million years of erosion, some rocks deposited by the ice-sheet can still be found. They are mostly an odd mixture of pebbles and boulders suspended in consolidated sand and mud. Some very large blocks left behind by the ice-sheet are called ‘erratics’ because they are unlike any local rocks.
The severity of the extinction at the end of the Permian meant that recovery was slow. The surviving marine life struggled to recover from the lingering effects of the mass extinction, such as significantly lower oxygen levels. The extinction of many corals left an empty niche, which was only filled by the evolution of modern scleractinian corals later in the Triassic. It took coral reefs millions of years to reform.
Survivors on land included insects, plants, amphibious tetrapods and some reptile groups – among them the ancestors of mammals, dinosaurs and birds.
There are few sedimentary rocks in Victoria dating from this period, so our knowledge is limited about the animals and plants that existed then. We do know that the world had no polar ice caps. Victoria had a mild climate despite being near the south pole. We can imagine the valleys, previously carved by glaciers, were now green with conifer forests and an understorey of ferns. They were probably home to amphibious tetrapods, reptiles and the earliest dinosaurs and mammals.
Some hardy animals survived the mass extinction. Lystrosaurus was a dicynodont, a group of plant-eating, mammal-like reptiles. Lystrosaurus probably lived close to water where surviving vegetation was more abundant after the mass extinction at the end of the Permian. Its simple, unfussy diet and possibly a burrowing habit might have helped it survive the extinction.
The warm, seasonal climate of the early Triassic set the scene for changes to plant life. ‘Seed ferns’ like Thinnfeldia were common plants at this time, and increasingly drier conditions saw the evolution of drought-resistant plants. Plant life spread from low-lying water margins and swamps, and the dry hillsides became populated by hardy trees and shrubs.
Australia's fossil record shows that during the Triassic the dominant plants were cycads, gingkoes, conifers and ferns like Thinnfeldia.
After the mass extinction at the end of the Permian there were few large carnivores. One group of reptiles called archosaurs evolved into efficient predators to fill this role, eventually giving rise to the crocodiles and dinosaurs.
The earliest dinosaurs were small, lightly-built and fast-moving predators such as Coelophysis which was two or three metres long. Dinosaurs had an anatomical advantage over other archosaurs – they had legs directly beneath their bodies rather than splaying out to the side, allowing for more agile and efficient movement.
Clatrotitan was a large insect distantly related to dragonflies. The fossil wings of Clatrotitan, found near Sydney, tell us something quite unusual – this insect was noisy. The wing had a ‘stridulating’ structure dedicated to making noise. By rubbing the wings against each other, a deep, resonating call was made, similar to modern cicada calls.
After the devastation of the extinction event at the end of the Permian only a few species of cephalopods survived – a pattern this group encountered in several other mass extinctions. Cladiscites was an ammonoid cephalopod. Although the fossil has a series of ornate squiggle patterns, these were internal structures called sutures that were not on the shell’s outer surface. Other fossils of Cladiscites show that the shell’s surface was finely ridged.
Birds and mammals evolve in the shadows of dinosaurs
Dinosaurs thrived in a world that was generally warm and had large areas of forest. The first mammals evolved beneath the shadow of the dinosaurs, and one group of dinosaurs gave rise to the first birds. The diverse ocean life included many species of fishes, marine reptiles and invertebrates.
Although Australia was quite close to the south pole it had a relatively warm climate, and the land was covered with forests of tropical conifers, podocarps and cycads. Dinosaurs large and small were dominant on land across the globe, although only a few of Australia’s dinosaurs are known from this time. Marine reptiles such as long-necked plesiosaurs hunted in the sea, and large cephalopod molluscs called ammonites caught prey with their tentacles. The movement of the Earth’s crust gradually began to break up Gondwana, and Australia started to pull away from Antarctica.
Birds evolved from a group of small theropod dinosaurs. Fossils of animals intermediate between birds and dinosaurs like Archaeopteryx show a combination of features from both groups. Archaeopteryx lived about 150 million years ago. It had a bony tail, a toothed jaw like a dinosaur and a wishbone like a bird. This reconstruction shows what it might have looked like.
A fossil of Archaeopteryx discovered in 1861 gave important support to the theory of evolution, as an example of an intermediate form between dinosaurs and birds.
Glyphea was a decapod – the large group of crustaceans that includes crabs, lobsters, prawns and shrimp. Fossils of Glyphea and their relatives tell an interesting story; this particular group of decapods was known only from fossils like this one until the 1970s, when it was discovered that close relatives of Glyphea were still living in the ocean near the Philippines.
On rare occasions, animals previously known only from fossils have been ‘rediscovered’ as living animals. These are nicknamed ‘Lazarus’ animals; creatures that appear to have ‘risen from the dead’, although they had clearly been alive all along, just difficult for humans to find!
Belemnites were a group of cephalopods resembling squid, and are related to the modern-day cuttlefish. They first appeared about 360 million years ago, but were most abundant in the Jurassic and the� Cretcaeous, becoming extinct at the same time as the dinosaurs. This species, Belemnites semihastatus, had an ink sac and ten arms like other members of the Belemnites.
Although fossils of their chambered internal shell called the phragmacone and small hooks that lined their grasping limbs have been found, the most commonly found remains of Belemnites are the bullet-shaped structures called guards. These were also internal structures, and they formed the tip of the phragmacone at the ‘tail end’ of the animals.
Reptiles rule as flowers evolve
At the start of the Cretaceous, the world was warm and free of polar ice caps. The largest animals were reptiles – dinosaurs, flying pterosaurs, dolphin-like ichthyosaurs and giant sea turtles. Mammals remained small. Flowering plants evolved and spread across the world.
All this changed 65.5 million years ago at the end of the Cretaceous when a major catastrophe led to the extinction of dinosaurs, many marine reptiles, all flying reptiles (pterosaurs) and many marine invertebrates. There is strong evidence that the culprit was a huge asteroid that formed a large crater on what is now the Yucatan Peninsula of Mexico. Vast clouds of dust produced by the impact would have blocked out sunlight across much of the Earth, killing plants and affecting the food chain for almost all animals. Smaller animals and those that could feed on detritus would have been able to survive.
Despite a warmer world, Victoria was still close to the south pole and it was one of the coolest places on the planet at the time. Victoria and Antarctica were covered in temperate forests of conifers and ferns. Many dinosaurs, some only the size of a chicken, adapted to life in these cooler forests, as did other reptiles, mammals and birds.
Life inside the polar forests of Victoria presented challenges to the dinosaurs that lived there, such as long periods with little sunlight. Fossils of Victorian dinosaurs show adaptations to coping with this environment, such as large eyes and an enlarged optic lobe – the part of the brain that interprets visual signals from the eyes.
Australia continued to separate from Gondwana, creating a rift valley with streams, forest and volcanoes. In the streams lived many species of fishes, aquatic reptiles, and ferocious amphibious tetrapods such as Koolasuchus.
Large predatory marine reptiles such as Platypterygius, an ichthyosaur, used their powerful tails to propel themselves through the warm inland sea that covered much of central and northern Australia in the Cretaceous. They used their sharp, ridged teeth and long snouts to catch fish and ammonites.
The skull of this ichthyosaur took a year to remove from the rock. The process involved dipping it into a bath of weak acid that dissolved the rock, but not the fossil. The fossil includes the whole ‘snout’ of the animal which makes it a rare find.
Muttaburrasaurus was a large plant-eating ornithopod dinosaur. It was once thought to be related to dinosaurs elsewhere in the world, but it is now considered to possibly be uniquely Australian. The skeleton was found in Queensland in the 1960s and is named after the town of Muttaburra.
Koolasuchus was a large predator belonging to an ancient group of amphibious tetrapods called temnospondyls. This group dominated for millions of years before virtual extinction at the end of the Triassic. The discovery of this Cretaceous Koolasuchus fossil near San Remo showed that the temnospondyls persisted in Victoria after they had died out elsewhere in the world.
Resembling something between a huge newt and a crocodile, Koolasuchus is thought to have lived in the cool streams of the Victorian rift valley, waiting to ambush its unsuspecting prey.
Mammals lived alongside dinosaurs for over 100 million years before the mass extinction that ended the age of dinosaurs. However, these mammals were generally small and were probably nocturnal.
Tonnes of rock were searched to find this tiny fossil. This mammal, called Bishops, was a small shrew-like creature that lived in the forests of the Victorian polar rift valley. Bishops is one of several types of mammals found in these Cretaceous sediments in Victoria, and for the most part it appears these mammals were extremely small.
The discovery in 1997 of tiny mammal jaws in Cretaceous sediments suggested that placental mammals, along with monotremes and an entirely extinct group of mammals called multituberculates, lived in Australia before marsupials, challenging previously held ideas about mammals in Australia.
Forests of tall conifer trees grew in the rift valley during the Cretaceous. These forests had an understorey of familiar-looking plants – relatives of today’s ferns and Ginkgo tree. Ginkgoites was quite common at this time; related to the modern-day tree Gingko biloba. Ferns like Cladophlebis were also abundant, providing food and shelter for small plant-eating dinosaurs.
Vast amounts of vegetation accumulated in parts of the valley, and over millions of years this plant material turned into seams of black coal. The thickest deposits were in Gippsland. The Wonthaggi coal mine produced 17 million tonnes between 1909 and 1968 – an important source of energy for Victoria.
This fossil of Qantassaurus intrepidus was discovered in Victoria. Qantassaurus was a type of small herbivorous dinosaur that lived in the forests of Victoria around 120 million years ago. They lived alongside a diversity of other dinosaurs, reptiles, mammals, birds and invertebrates. Qantassaurus was named after the airline Qantas in recognition of the company’s support of dinosaur research and education.
Qantassaurus had a beak-like mouth for nipping at vegetation, ridged teeth and muscular cheeks for chewing – a perfect combination for reducing fibrous ferns to a pulp. It ran on powerful legs using its long tail for balance.
At the end of the Cretaceous Period, it was not only dinosaurs and pterosaurs that disappeared. Sea life also suffered, and cephalopods like this ammonite became extinct.
Most ammonites had a spiral-shaped shell, however some Cretaceous ammonites showed some interesting variations in shell form. The shell of Bostrychoceras was helical, and had an almost turret-like shape. Other Cretaceous ammonites showed even more unusual shell forms. This diversity came to an abrupt end at the mass extinction event at the end of the Cretaceous.
Modern animal groups
Following the extinction of the dinosaurs, the surviving birds, mammals and reptiles diversified. Drifting continents continued to change the face of the planet, building mountains, creating new ocean currents and causing major climate changes.
The extinction of the giant marine reptiles left the niche of large ocean predators vacant. In the warm oceans, early whales evolved from hoofed, deer-like land mammals that lived in shallow water. When Australia and South America separated from Antarctica, cool water began circulating around the pole. Plankton thrived there and plankton-feeding baleen whales evolved.
Tropical and temperate forests covered large areas of Australia. The area we know as Bass Strait was largely dry land with floodplains, lakes and peaty swamps bordered by forest, and seams of brown coal began to form. During several periods of significant volcanic eruptions in Victoria, lava flows covered parts of western and central Victoria. Australia’s marsupial mammals began to diversify in isolation, evolving into carnivores, herbivores and scavengers. High sea levels frequently covered parts of the continent and the skeletons of bryozoans, echinoderms, molluscs and other animals that thrived here created the large volume of limestone deposits that now form most of the coast along southern Australia.
* The Tertiary is an informal term originally given to this period of time in the 1800s. While not recognised by the International Commission of Stratigraphy, it is still in common use to describe collectively the Paleocene, Eocene, Oligocene, Miocene and Pliocene epochs.
Around 50 million years ago southern Australia was blanketed in tropical rainforest. Near Anglesea in southern Victoria this rainforest bordered streams crossing a floodplain, and masses of leaves fell onto soft sediments and were quickly covered.
The fossil leaves that were preserved are like a time capsule that reveals what the environment was like. These fossil leaves were extracted from the rock using a specialised technique that preserves their fine detail – complete with internal tissue, looking like a leaf plucked from fresh leaf litter.
Picture a shark’s mouth so large you could walk inside it. This fossil tooth is from an extinct shark called Carcharocles megalodon, sometimes simply called Megalodon or ‘Meg’.
These sharks were apex predators in the oceans, and were the largest sharks known. Fossilised teeth like these have been found in locations around the world, suggesting that Megalodon was widespread. This fossil is from a site near the Victorian town of Hamilton.
This marsupial was a browsing herbivore from the ancient forests of the Northern Territory. The occurrence of browsing marsupials like Neohelos rather than grazing marsupials reflects the nature of the environment at the time – browsers fed on the more abundant shrubs and trees, whereas grazers, like many kangaroos, feed on grass. Neohelos represents an animal adapted to conditions prior to the expansion of the grassland habitats in Australia.
Neohelos was roughly the size of a calf, with adult males being larger than the females. About 12 million years old, Neohelos is an early ancestor of marsupial megafauna that would later dominate the Australian landscape.
Crocodiles and their relatives (called crocodylomorphs) have a long fossil history going back to the Triassic, evolving around the same time as the first dinosaurs.
This fossilised skull is not as old as the first crocodiles, but it is still around 40 million years old. The fossil is from a crocodile genus called Kambara, a uniquely Australian group of crocodiles that are now extinct. The crocodiles living in Australia today originated from a different group that reached our shores from Asia millions of years after Kambara went extinct.
Janjucetus was a small whale that lived around 25 million years ago off the Victorian coast. It hunted large fish for food, gripping them between its sharp teeth with the help of powerful jaw muscles.
Despite having fearsome teeth, the skull bones of Janjucetus show that it was in fact a very primitive baleen whale – but without baleen. Janjucetus is therefore a vivid evolutionary link between ancient whales and the modern Blue Whale.
This collection of fossilised seed pods, nuts and fruiting bodies found in a gold mine near Ballarat belong to plant families that gave rise to the modern Australian flora.
The climate in Australia cooled around 30 million years ago and the lush rainforest covering Victoria eventually gave way to temperate forests. Land fossils from Australia at this time are rare, so these well-preserved fossils of the fruiting bodies of plants provide valuable clues to the changing environments in Victoria.
The brown coal deposits in the Latrobe Valley are the largest of their type in the world. They formed over a period of 30 million years as vegetation from luxuriant forests accumulated and decomposed in swamps as the Gippsland Basin subsided. The swamps began to dry about 10 million years ago and were covered by sediments.
Quipollornis was an ancestor of the modern-day owlet-nightjars, small nocturnal birds related to frogmouths and nightjars. Quipollornis is known only from a single fossilised flattened skeleton. It probably hunted by ‘hawking’ for moths and insects over tree-lined rivers and lakes 15 million years ago in central New South Wales.
Megafauna around the globe
While the world map now looks familiar, we cannot see the impacts of dramatic changes caused by a series of ice ages. Lower sea levels – one effect of these ice ages – created land bridges. Large animals, collectively called megafauna, lived throughout the world at this time. Mammoths, sabre-toothed cats and giant deer lived in the Northern Hemisphere while giant marsupials such as Diprotodon, enormous goannas and large flightless birds distantly related to ducks and geese roamed Australia.
The bedrock of modern Victoria was in place, but the landscape continued to change. Volcanoes were active again. The climate became drier, rainforests shrank, and plants and animals suited to dry conditions spread. Hard-leaved plants such as eucalypts, spinifex, banksias and wattles were food for animals ranging from termites to marsupials. Megafauna shared the landscape with more familiar animals such as kangaroos and emus. Humans probably arrived in Australia 60 000–50 000 years ago. These Aboriginal people adapted to the landscape they found and developed an intimate knowledge of its life and the resources it offered.
*The lower boundary of the Quaternary period is subject to debate. It includes the Pleistocene and Holocene epochs.
Volcanoes have shaped Victoria for millions of years. The most recent period of volcanic activity was between about five million and a few thousand years ago.
Aboriginal people witnessed some of the most recent eruptions. Well-preserved volcanic features such as craters, crater lakes and lava flows can be seen in western Victoria today.
Despite its size and robust appearance, Diprotodon’s skull was lightly built and was as thin as eggshell in places. Consequently, a complete, unbroken skull such as this one found near Bacchus Marsh, is a rare find. The feet of Diprotodon were also unusual; the fossil foot bones and preserved footprints indicate that it walked with its hind feet turned slightly inwards. These feet needed to support the weight of the largest marsupial to have lived.
Palorchestes was a large marsupial herbivore that browsed forest shrubs. When fossilised Palorchestes teeth were first discovered, they were thought to be from a giant kangaroo. As more fossils were discovered it became clear that the narrow skull, powerful legs and long claws made Palorchestes quite different from any living animal.
This Palorchestes skull is the most complete in Australia, preserving the thin bones of the brain case. Discoveries like this, from a cave near Buchan in eastern Victoria, help us understand what this animal looked like.
With its homely, pushed-in face and solid, stout body, Zygomaturus is sometimes called the ‘marsupial rhino’. This nearly complete skeleton was found in Mowbray Swamp in Tasmania. Zygomaturus was a robust herbivore that lived in the forested areas of southern Australia. It browsed on low vegetation near water.
These footprints were found in a dry lake bed in Western Victoria. The giant marsupial Diprotodon, along with wombats and kangaroos, left tracks as they walked across soft volcanic mud about 100 000 years ago. These tracks were moulded and cast by museum preparators to record the tracks for display and scientific study.
This fearsome carnivore was the top predator in Australian until 45 000 years ago. Although a specialised carnivore, Thylacoleo was descended from herbivorous marsupials. It preyed on kangaroos and other animals and could bite clean through their limbs with its powerful jaws and shearing teeth.
This skeleton shows some features that made Thylacoleo a formidable predator. Forward-facing eyes, retractable claws and teeth capable of disabling prey earned it the nickname the ‘marsupial lion’.
Mt William greenstone was an important resource for the Wurundjeri people of south-eastern Australia. They quarried the hard stone to make ground-edged stone hatchets, general purpose tools for splitting, cutting and shaping wood and for butchering animals. Greenstone hatchets were highly valued and were traded over hundreds of kilometres.
Today’s kangaroos have some weird and alarming ancestors. The largest living kangaroo is the Red Kangaroo, standing nearly two metres tall. But even the largest ‘big red’ would have been dwarfed by Procoptodon, the largest of the extinct macropods. It had a short, flattened snout, making the skull look a little like a giant human skull.
A smaller relative of this giant was Simosthenurus, which also had a short face with teeth adapted for browsing shrubs.
Protemnodon was a diverse genus of forest-dwelling wallabies that is now extinct. The name means ‘front-cutting teeth’, which describes their distinctive, blade-shaped premolar tooth.