C. megalodon Extinct by 2.6 million Years Ago

The giant prehistoric shark known as Megalodon (C. megalodon) has certainly attracted a lot of scientific attention in recent years.  This predatory shark, believed to be the largest, carnivorous shark to have ever existed, might have reached lengths in excess of sixteen metres.  Bodyweight estimates vary, but a number of scientists have calculated weights around the twenty tonnes mark.  With a mouth that could gape nearly 3 metres wide, this fish would have been capable of swallowing an extant Great White shark (C. carcharias) whole!

Megalodon Still Exists?

Some fishermen, such as those who fish the waters off South Africa have claimed that Megalodon still exists, but a team of researchers from the University of Zurich and Florida University have used a statistical technique to provide the best estimate yet of the extinction of this apex marine predator.

Safari Ltd Introduced a Model of the Giant Shark Known as Megalodon this Year

Fearsome marine predator.

Picture credit: Everything Dinosaur

To view the range of Safari Ltd prehistoric animal models: Safari Ltd. Prehistoric World Figures.

Megalodon Extinction

Writing in the on line journal PLOS One (Public Library of Science), the researchers Catalina Pimiento (Department of Biology, University of Florida) and Christopher Clements, (Institute of Evolutionary Biology and Environmental Studies, Zurich University), used a statistical analysis to calculate the approximate time of the extinction of these predators.

By developing a better understanding of the time of the extinction, the research team are able to map the consequences of the extinction of an apex predator on the marine ecosystem.  Using a mathematical technique called Optimal Linear Estimation (OLE) the scientists have calculated that around 2.6 million years ago C. megalodon became extinct.  This is the first time the extinction of C. megalodon has been quantitatively assessed.

A total of fifty-three fossils of this ancient shark were used in this study, but this number was reduced to forty-two for the statistical assessment, as eleven of the fossil specimens gave the researchers less confidence over their actual age.

Optimal Linear Estimation

Optimal Linear Estimation is used for mapping the extinction of modern species, but with the abundant and widespread fossil record of Megalodon, mainly the large number of fossilised teeth associated with this species, the team were able to apply this mathematical method to calculate the time when the very last of these magnificent creatures lived.

Fossilised Tooth from C. megalodon

A large fossil tooth from a Carcharodon megalodon. Picture credit: Everything Dinosaur.

 Picture credit: Everything Dinosaur

Although the team admit that their calculations are subject to margins of error, this work represents a refinement on previous estimates of the extinction of this shark species.  Why this apex predator became extinct remains a mystery

Megalodon Fossil Material from the Miocene

Most Megalodon fossil material dates from around 16 to 11.6 million years ago (Miocene Epoch) with some further fossils known from the Pleistocene Epoch, although a lot of the fossil material associated with Pleistocene deposits were not included in this particular study.  With a more accurate extinction date established, the researchers can then assess the impact of the removal of a large predator from the marine environment on other genera including cetaceans.

The date of 2.6 million years ago marks the border between the Pliocene and Pleistocene Epochs, it was after this point that the baleen whales began to increase in size and to evolve into the many giant forms alive today.

Did Whales Flourish When Megalodon Became Extinct?

As marine mammals are thought to have made up a substantial part of the bus-sized shark’s diet, although there is no conclusive evidence to suggest Megalodon fed on large whales, if Megalodon died out, did this trigger the flourishing of the baleen whales?

Commenting on the research, Catalina Pimiento stated:

“When we calculated the time of Megalodon’s extinction, we noticed that the modern function and gigantic sizes of filter feeder whales became established around that time.  Future research will investigate if Megalodon’s extinction played a part in the evolution of these new classes of whales.”

Megalodon is a prime candidate for this sort of statistical analysis, due to the relative abundance and widespread distribution of its fossilised teeth.  It is hoped that this technique can be applied to other extinct species to plot more accurately the impact of a single species extinction on the wider ecosystem.

The PNSO Megalodon Model

The amazing, colourful sleeve artwork on the PNSO Megalodon figure.

Note

Following a taxonomic revision this prehistoric shark is now known as Otodus megalodon.

New Study Sniffs Out Details of the Pachycephalosaur Nose

A study into the nasal passages conducted by a team of scientists from Ohio University suggests that certain types of dinosaur used their complicated noses to help cool their brains as well as to enhance their ability to smell.  A new study has got to grips with the noses of dinosaurs.

The Noses of Dinosaurs

The study, which focused on specimens from the Pachycephalosauridae family (the bone-heads), involved the development of computer models derived from CT scans of fossilised skulls in order to map the airflow in and out of a dinosaur’s snout.  Palaeontologists have known for some time that a number of different types of dinosaur had very complex nasal passages.  The nasal region although mostly associated with breathing (respiration), also plays an important role in helping to define and enhance a creature’s sense of smell.  In addition, the ability to bring in air at an ambient temperature into the skull may have a function in helping the brain to keep cool.

In the Late Cretaceous of North America, Pachycephalosaurs may have had small brains in their heavily armoured skulls but they did not want them to cook inside those thick heads.

A Model of a Typical Member of the Pachycephalosauridae Family

Nosing around the nasal passages of dinosaurs.

Picture credit: Everything Dinosaur

Lead author of the research, which has just been published in the academic journal “The Anatomical Record”, Jason Bourke (Ohio University) states:

“Figuring out what’s going on in their [dinosaurs] complicated snouts is challenging because noses have so many different functions.  It doesn’t help that all the delicate soft tissues rotted away millions of years ago.”

Examining the Nasal Passages

In order to gain an appreciation of the nasal passages of long extinct dinosaurs, the team examined the snouts of extant relatives of the Dinosauria, namely birds, crocodiles and other reptiles including lizards.  The study of fossil skulls of pachycephalosaurs was supported by lots of dissections, blood-vessel injections to map blood flow as well as CT scans.  The researchers also relied upon computer models that provided a three-dimensional analysis of airflow.

A technique more commonly applied to the study of airflow in the aerospace industry, a technique called computational fluid dynamics was used to better understand how extant animals such as Alligators and Ostriches breathe.

As PhD student Jason Bourke explained:

“Once we got a handle on how animals breathe today, the tricky part was finding a good candidate among the dinosaurs to test our methods.”

The team turned to a family of bird-hipped dinosaurs known as the pachycephalosaurs, the bone-headed dinosaurs.  These particular dinosaurs were chosen as a number of specimens were readily available to study in the United States/Canada and skulls attributed to several genera were known.   The thick skulls with their ornamentation may have been used  by these relatively small dinosaurs for head-butting or visual displays.  The skull bones, some of which are several inches thick, has helped to preserve details of the nasal passages which the scientists were able to map and analyse in great detail.

Getting Up a Dinosaur’s Nose

Airflow in the nasal passages in the Pachycephalosaur Stegoceras validum is mapped.

Picture credit: Ohio University/The Anatomical Record

Studying Stegoceras

One pachycephalosaur that was studied was Stegoceras (S. validum) and the researchers were able to show that some of the airflow that they mapped would have carried odours to the olfactory region, helping to improve this dinosaur’s sense of smell.  In addition, the team tried to piece together the shape of the nasal concha, otherwise known as the turbinates, that help to direct and manage airflow through the nasal passage.  This small bone, superficially resembles a sea shell (hence the name) and the fossil evidence supports the presence of such a bone but it is not found in the Dinosauria fossil record (as far as we at Everything Dinosaur know).

As the researchers point out, there is the bony ridge preserved on pachycephalosaur skulls that indicate its presence and when airflow models were created, the best and most efficient ones produced included a turbinate structure within the model.

Commenting on the research results, Jason Bourke stated:

“We don’t really know what the exact shape of the respiratory turbinate was in Stegoceras, but we know that some kind of baffle had to be there.”

Study co-author Ruger Porter (Ohio University), pointed out that turbinates may well direct air to the olfactory region, but they might have also played another critical role, helping to cool the brain or at least helping to conserve moisture that might have been lost during exhalation.

Porter pointed out:

“The fossil evidence suggests that Stegoceras was basically similar to an Ostrich or an Alligator.  Hot arterial blood from the body was cooled as it passed over the respiratory turbinates and then that cooled venous blood returned to the brain.”

Endothermic Implications?

Whether this new research supports the theory that these dinosaurs were warm-blooded (endothermic) is being debated, but it does suggest there was more going on within dinosaur’s noses than scientists had previously thought.  It is hoped that the research team will be able to apply their analytical methods to other types of dinosaur such as the Thyreophora (armoured dinosaurs), known for their notoriously complex nasal passages.  This research may also provide answers to the questions concerning the bizarre shape of many crests found in lambeosaurine dinosaurs (duck-billed dinosaurs).

For models and figures of dinosaurs and other prehistoric creatures: CollectA Prehistoric Life Models and Figures.

Giant Sthenurine Kangaroos Probably Walked Rather Than Hopped

The Pleistocene prehistoric fauna of Australia may not quite be as embedded into the public’s consciousness as the Woolly Mammoths, Cave Bears and Sabre-toothed cats that represent examples of European Pleistocene prehistoric animals, but if anything, ancient “Aussies” were even more amazing than the shaggy coated examples typical of the fauna of the western hemisphere.

Giant Kangaroos

In a new study, published in the on line academic journal PLOS One (Public Library of Science), a team of researchers propose that ancient, giant Australian Kangaroos were walkers rather than hoppers, making up part of a prehistoric fauna that was truly astonishing.

The Kangaroos in question are the heavy-weight members of the Sthenurinae (the short-faced kangaroos).  A sub-family of the Macropodidae (means “big feet”), the family to which all Kangaroos belong.  Following a rigorous comparative analysis, the research team conclude that these large animals, some of which stood over two metres tall, did not hop but were adapted to a pedestrian lifestyle, these animals were walkers.

Sadly, like most of Australia’s mega fauna these herbivores became extinct and did not make it into the Holocene.  The last of the Sthenurinae died out about 30,000 years ago, shortly before the last of the Neanderthals in western Europe.

A Comparison Between an Extant Sthenurinae Kangaroo (Sthenurus stirlingi) and a Large Extant Species

Both these types of Kangaroo can stand up to two metres tall.

Picture credit: Wells and Tedford, 1995.  Original artist Lorraine Meeker, American Museum of Natural History, with additional annotation from Everything Dinosaur

Extinction Theories

As for reasons for their extinction, that question remains to be answered, however, it is thought that the presence of man on the continent from around 60,000 years ago had a severe impact on the fauna of Australia.  Giant Short-faced Kangaroos such as Simosthenurus occidentalis (short-faced, strong tail, western Kangaroo), known from fossils found in south-western Australia, probably could not move very quickly and could be caught by human hunters.  The use of fire could also have devastated their forest habitats leaving these browsers with little food.

The research team was led by Professor Christine Janis, (Professor of Ecology and Evolutionary Biology at Brown University, Rhode Island, USA).  Over one hundred comparative measurements were made, comparing the skeletons of living and extinct Kangaroo and Wallaby types.  For Professor Janis, her eureka moment occurred in 2005.  She was examining the bones of a mounted skeleton of a sthenurine Kangaroo in a Sydney museum when she noticed how inflexible the spine looked when compared to a modern-day counterpart.  The professor began to wander whether these Pleistocene roos moved in the same way as extant Kangaroos.

Extinct Sthenurines

Working in collaboration with the papers co-authors, Borja Figuerido of the University of Malaga (Spain) and Karalyn Kuchenbecker, a former undergraduate at Brown University, the Professor spent several years examining the fossilised remains of extinct Kangaroos to determine their method of locomotion.  In the published account of their studies, the team hypothesise that in their motion the extinct sthenurines were very different from large Kangaroos found today.  The scientific paper is intriguing entitled: “Locomotion in Extinct Giant Kangaroos: Were the Sthenurines Hop-Less Monsters?”.

Extant Kangaroos can hop very quickly and utilise this unique form of motion to cover vast distances very efficiently.  They can also move about on all fours as their front limbs are capable of helping to support bodyweight, an anatomical characteristic absent in the larger members of the Sthenurinae.  The tail of many members of the Macropodidae is also able to bear weight, providing additional support for many Kangaroos and Wallabies.  The use of the tail as a fifth limb has been referred to as a “pentapedal” stance.  Extinct Kangaroos such as Sthenurus stirlingi seem to lack the flexible spine need to make leaps and bounds.  Their anatomy seems best suited to putting one foot in front of the other – a walking Kangaroo!

Sthenurines had proportionally bigger hip and knee joints.  The shape of the pelvic area differs significantly as well (see diagram above).  The sthenurines had a broad and flared pelvis that would have allowed for proportionally much larger gluteal muscles than other Kangaroos.  Those muscles would have allowed them to balance weight over just one leg at a time, as do the large gluteals of humans during walking.

One Massive Toe

Unlike modern Kangaroos with their four-toed feet, the extinct sthenurines had just one, massive toe on the end of each foot.  The research team conclude that when the anatomy of all the Macropodidae is considered, the “weird” ones are the extant species that hop.  They are very lightly built for their size and their preferred method of locomotion may not be typical for the group as a whole.  A bit like using the Cheetah as a template for all Felidae motion.

Commenting on the research Professor Janis stated:

“If it is not possible in terms of biomechanics to hop at very slow speeds, particularly if you are a big animal and you cannot easily do pentapedal locomotion, then what do you have left?  You have to move somehow.”

An over reliance on walking, which is not as efficient as hopping, might explain the demise of these Kangaroos about 30,000 years ago.  These animals might have been easier to catch so humans took a toll on the population.  Or as the climate became more arid, these walking Kangaroos were not able to migrate far enough to find new sources of food.

An Artist’s Impression of a Short-Faced Kangaroo

Short-faced Kangaroo a pedestrian.

Picture credit: Brian Regal

The research team admit that more evidence is required to back up their anatomical study.  Ideally, if a set of “walking Kangaroo” tracks could be discovered, that would add considerable weight to their hypothesis.

Oldest Prehistoric Cave Art in the World Perhaps – An Indonesian Cave Art Exhibition

The human ability to think in abstract terms is often cited as one of the key differences between our species and those in the rest of the animal kingdom.  Our love of art and visual depiction can be traced back to the Late Palaeolithic but the thought that since cave paintings are confined to France and Spain, therefore art began in Europe, has been challenged thanks to an amazing discovery on the Indonesian island of Sulawesi.

A joint Australian and Indonesian team of anthropologists have uncovered a series of ancient human hand stencils and paintings of animals in seven cave sites in the southern portion of Sulawesi island.  Although a rural location, these caves (Karst Maros) had been visited by a number of tourists and backpackers, but until now nobody knew just how old some of the paintings were.

Cave Paintings

Archaeologists and palaeoanthropologists had long been puzzled by the appearance in southern Europe around 40-35 thousand years ago of a rich and varied range of artwork, including rock paintings and carved figures, but the absence or scarcity of similar art found elsewhere in the world.  Homo sapiens migrated into southern Asia and the Far East but little evidence of any form of culture in terms of works of art has been left behind on these migration routes.

Using a dating method that is based on the radioactive decay of uranium to thorium in small mineral growths that had formed on the paintings, the scientists were able to determine the minimum age of the paintings.  One hand stencil has been dated to circa 39,900 years ago, making it the oldest human hand print known to science.  A painting of a wild pig, an animal probably hunted by these ancient humans, has been dated to at least 35,400 years ago.  The artwork and images had been created by using red ochre, the materials and painting techniques used seem to be very similar to those found in caves of a similar age in western Europe.

Symbolic Explosion

Commenting on the significance of this study, Maxine Aubert of Griffith University (Queensland), one of the researchers stated:

“It was previously thought that Western Europe was the centre piece of a symbolic explosion in early human artistic activity such as cave painting and other forms of image making, including figurative art, around 40,000 years ago.”

This new research suggests that the rock art traditions seen on Sulawesi are at least as old as the oldest known European art.   One of the implications of this new study is that it has now been demonstrated that humans were producing very similar types of rock art by 40,000 years ago but at opposite ends of the Pleistocene Eurasian world.

Faded Artwork

The artwork is very faded in the photographs, so we have circled in green the rock art in the images that was studied.  It is feared, that just like the cave art in some European caves, modern pollution could damage these ancient Indonesian drawings.

To read an article about the damage being done to cave paintings in Europe due to rising levels of fungi: Cave Paintings Might Be Lost Forever.

The scientists hope to use this radioactive dating technique to accurately date other rock art sites in Asia and Australia.  By doing this they hope to better understand human migration and the movement of abstract ideas through the ancient population as it migrated eastwards.

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