fossils

Dinosaurs down under

3986b46bb4f35aa1ff4d42167a12e0fc

Vasika
Udurawane

Writer
For millions of years, a wide variety of dinosaurs battled harsh, wintry conditions as the Southern Lights flickered above their heads. These unique pioneer discoveries of paleontology, some gigantic and some petite, have all left their remains in opal and rock in the “Land Down Under.”

Australia has been undergoing numerous changes over millions of years, but none so spectacular as those it experienced during the long reign of the dinosaurs. The country was not always known for being a major dinosaur hotspot, but recent findings have unearthed a vast number from all corners of the country. From gargantuan long-necked behemoths to small, fluffy forest-dwellers and some speedy predators in between, the dinosaur fauna of the continent has always been surprising, turning preexisting paleontological theories on their head many times over. Despite this though, many of the dinosaurs still remain nameless.


One particular surprise was the so-called Lightning Claw, widely popularized as Australia’s biggest dinosaur predator. The fossils were acquired in 2005 from the small town of Lightning Ridge. The bones were found in an opal mine, a rather common occurrence, and the remains had also been turned into opal. While the animal’s remains are incomplete, they correspond to a creature possibly 7 meters long. This is hardly a giant in comparison to some of the real heavyweight carnivores of the dinosaur world but is still big enough to make it famous. The Lightning Claw was probably slender and graceful, using both the claws on its hands, plus its slicing teeth, to render its prey helpless. Another surprise was the discovery of a few vertebrae from a fish-eating spinosaur. It was an animal related to the famous Baryonyx from England. Both of these were large predators, although the lack of a name makes for a frustrating turn of affairs.


Among the earliest dinosaur fossils to be found were discovered in a location in the Cape Otway area in Victoria, in the nation’s southern frontier. In 1903, a geologist named William Hamilton Ferguson discovered the country’s first dinosaur bone, a toe claw, at a location known as Eagle’s Nest, somewhat west of Inverloch. This of course created a sudden surge in interest, as many more museums and volunteers set out to the same location to unearth more remains. By 1978, Rob Glenie and a small team of fellow volunteers explored the area and subsequent expeditions uncovered even more complete, and much better fossil remains. Very soon this site was known as Dinosaur Cove and it was titled one of the richest Australian bonebeds.


There is a number of separate formations here, including Dinosaur Cove East, Dinosaur Cove West and Slippery Rocks. These rocks are around 106 million years old and correspond to the Early Cretaceous. Around nine to thirteen million years older are the rocks at Strzelecki, a markedly similar dinosaur site, and from roughly the same area. Both of these sites have revealed a very unique and seasonal environment in which we do not typically picture dinosaurs. Here, we had both temperate floodplains and so-called polar forests. It is at Strzelecki that we see the best plant fossils, including ferns, cycads, araucaria and ginkgos. Even insects, mammals and fish have been found here, thus providing a nearly complete look at the contemporary ecosystem.


Unidentified spinosaurid by Fabrizio De Rossi


Studies of oxygen isotopes revealed that summers were somewhat mild while winters were incredibly cold and there were six months of complete darkness, even if there were no ice caps at the poles. Average temperatures were around -12 to 8 degrees Celsius. One more key factor is the location of the site: Australia was once a part of Antarctica, and Victoria in particular was directly in the Antarctic Circle of the time. This very factor changed many old views of the dinosaurs as slow-moving cold-blooded monsters. Here they were, a number of tiny and agile animals that were clearly very hardy and adapted to life in the cold. The rocks here also show that Gondwana was going through a great amount of change. One finding shows how Australia was breaking away from the Gondwanan landmass during this period, especially at the ancient Otway and Strzelecki Groups area. These two mountain chains were laid down during the time when the continents were splitting, when vast amounts of sediment were lifted up from the ground. At the time, there was just a rift valley.


Leaellynasaura by Julio Lacerda


Dinosaur Cove was also explored by well-known paleontologists like Thomas and Patricia Rich, who found some of the most complete dinosaurs from the area during their expeditions. To find the fossils, their teams either dug or dynamited the surrounding rocks, with the latter method being both useful and somewhat destructive. Many of the dinosaurs here in particular were small, although the implications the fossils carried were both huge and life-changing. The couple’s children Tim and Leaellyn sometimes accompanied their parents on fossil hunts and one of the most popular Aussie dinosaurs owes its name to the girl of the family. It was a surprising little animal called Leaellynasaura, a dinosaur that killed old ideas about these animals for many years to come.


Leaellynasaura was between one and three meters long and lightly built. It was a herbivore that probably browsed among the understory plants of the polar forests. The animal had the characteristics of many of its kind, from the two-footed stance to the narrow head of a small and possibly selective eater.


It also had no strengthening ossified tendons in its incredibly long tail. This lack of strengthening structures may have made it highly flexible and the purposes of such an appendage have been debated. Some argue that Leaellynasaura used it for communication like some animals do today. Others ascertain that the animal would rest by wrapping its tail around its body like a squirrel. Studies of the little dinosaur’s skull show that it was probably active even in winter. Complete fossils of other small herbivores like itself have revealed that these animals had a coat of soft feathers or at least primitive feather-like filaments. Leaellynasaura is also thus restored with this kind of integument, making it arguably one of the most adorable dinosaurs in the popular consciousness.


Muttaburrasaurus by Nathan Rogers


There were, of course, much larger herbivores around. One of these was the big browser Muttaburrasaurus, an animal that made waves due to possibly having a skin balloon which it could inflate to make trumpeting calls. The part of the skull around the nose is indeed quite high, but whether or not it had such a structure is still up for debate. The rest of its head is somewhat flat and narrow and possibly bore a beak in the front of the jaws. It was far larger than its contemporary relatives at around eight meters in length, and weighing around three tons. Just like them though, it was probably a two-footed animal. It was a rather primitive, or basal animal despite its large size. This dinosaur is also from the Early Cretaceous, and it gets its name from Muttaburra in Queensland. The fossils were discovered close to the Rosebery Downs Station near Thomson River, but others were soon found further afield. For a long time, it was one of the most complete Aussie dinosaurs, and also one of the best represented, with fossils known from Lightning Ridge in New South Wales, as well as in Hughenden, Queensland. Possible tracks of Muttaburrasaurus or a dinosaur of similar proportions have also been found, at a location called Lark Quarry.


Lark Quarry is famous for preserving a supposed dinosaur stampede, in which a number of tiny carnivorous and herbivorous dinosaurs were all thought to have been chased through a wetland area by a large predator. More recent research suggests that rather than a single dramatic event, the different sets of tracks were laid down at different times. Also, the supposed big carnivore might in reality have been just a large, passing herbivore. The quarry is a little way off the Queensland town of Winton, another major dinosaur site.


Australovenator by Julio Lacerda


One of the latest Australian dinosaur-bearing beds is the Winton Formation, which dates back to the dying days of the Early Cretaceous. It is between 108 and 93.9 million years old, and shows how the split in southern Gondwana began to widen the gap between continents. The landscape seems to have been growing much more swampy, with a totally new cast of characters making their living in the area. One of these was the apex predator of Winton, which is also Australia’s best-known carnivorous dinosaur. It is known as Australovenator. This speedy, lightly-built creature was described and named by Scott Hocknull and colleagues in 2009 and it soon became well known thanks to numerous press release images. It was rather small, around five meters in length and probably wasn’t going after huge prey. It had a small, narrow head, long legs and long arms tipped with sharp claws, somewhat like those of “Lightning Claw” and the two might have been close relatives.


The Winton’s biggest herbivores were none other than its titanosaurs. Currently the best-known of these is Diamantinasaurus, a robust and probably armored animal up to 16 meters in length. It towered over its contemporary predator, suggesting that Australovenator had to go after the juveniles rather than taking on the mighty adults head-on. Both these dinosaurs were contemporaries from a part of Winton called the “Matilda Site”. Despite its size, Diamantinasaurus, nicknamed Matilda in the press, was not the biggest Aussie beast. Rather that title might go even more as-yet unnamed titanosaurs from the Winton Formation’s uppermost reaches. This puts them as mid-Cretaceous dinosaurs, around 98 to 95 million years old. Not much of these supposed giants is known. Remains of these titanosaurs were discovered in 2004, quite by accident. The fossils consisted of many limb elements including an arm bone and a femur. Soon after, Scott Hocknull and a team of scientists began to excavate the remains of a number of dinosaurs, most of which were huge, heavily-built and long-necked titanosaurs.


Diamantinasaurus by Oliver Demuth


They included Cooper and George, the biggest native dinosaurs known from any good remains. Hocknull and his team estimate that these creatures might have reached 25 meters in total length and weighed 40 tons, which in reality is a good deal smaller than the real record-breakers. Still, it is an incredible find, although the utter lack of a proper name has somewhat irked the scientific community for a while. Even more frustrating is another giant, somewhat earlier than Cooper and known only from its tracks. In 1994, Tony Thulborn discovered a series of vast footprints in an area called Broome in Western Australia. The fossil footprints were estimated to be at least 1.5 meters long, and may correspond to an earth-shattering colossus far bigger even than the Winton giants. This so-called Broome titanosaur’s true dimensions are as yet unknown due to the lack of any good body fossils and whether or not it could exceed the record holders like Argentinosaurus, Alamosaurus and Puertasaurus is also yet to be seen.


For the time being though, certain smaller dinosaurs are coming out of the woodwork in such detail that they are the country’s most complete dinosaur fossils. These remains belong to a tiny armored dinosaur called Kunbarrasaurus. The animal’s fossils were found in 1989 in the Allaru Mudstone Formation of Queensland. The bones are between 119 and 113 million years old. For a long time it was classified as something completely different but was reclassified last year by a team comprising Lucy G. Leahy, Kenneth Carpenter, Ralph Molnar and others. The fossils of Kunbarrasaurus represent a kind of animal that is known from Australia but never in such detail as this. The animal’s skull is incredible in its completeness, so much so that CAT scans have revealed the structure of its brain and the areas devoted to smell, the olfactory canals.


The head was somewhat like that of a big turtle’s, with a beak at the end for cropping low-growing vegetation. Even the gut contents of Kunbarrasaurus have been preserved, and indicate a diet of stems, leaves and anything else its little jaws could reach. Kunbarrasaurus used its jaws to process its food and could likely chew its meals instead of relying on stomach stones called gastroliths. In life, the creature was low-slung, somewhat like a walking coffee table studded with armored plates that made it a tricky target for a hunter close to its size. At barely three meters long, it was not a large dinosaur, even though its armor made it rather slow-moving. As the most complete dinosaur out of an arguably short list, Kunbarrasaurus shows us that the field of paleontology is thriving in Australia and newer dinosaurs will continue to reveal their secrets as the years go by.

Image Credit: Oliver Demuth, Julio Lacerda, Fabrizio De Rossi, and Nathan Rogers

3986b46bb4f35aa1ff4d42167a12e0fc

Vasika
Udurawane

Writer


http://sulc.us/cpbkp
http://www.eartharchives.org/articles/dinosaurs-down-under/