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DISPLAYING POSTS TAGGED: palaeontology (13)

Whale vs shark

Author
by Ursula
Publish date
7 February 2012
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Comments (1)

Ursula Smith works in the natural sciences collections at Museum Victoria. Though a palaeontologist by training she finds all the collections fascinating and swings between excitement at all the cool stuff in them and despair at the lack of time to look at it all.

This cabinet contains parts of the skeleton of a fossil whale collected at Bells Beach, on the Surf Coast southwest of Melbourne.

collection cabinet Vertebrate Palaeontology Collection storage cabinet full of fossils.
Source: Museum Victoria
 

This story is only indirectly about that whale, but it does start with one of its bones:

Fossilised whale bone. Fossilised whale bone.
Source: Museum Victoria
 

This is a metacarpal – a bone from one of the whale's flippers (forelimbs). Here, it's being held by Dr Erich Fitzgerald, Senior Curator of Vertebrate Palaeontology and Harold Mitchell Fellow at Museum Victoria, which gives you an idea of the size – it's about 7cm long. The equivalent bone in a human hand (the bone that runs between your middle finger and your wrist) is about the same length, though not as chunky.

At the top of the bone, you can see two grooves that make an inverted 'V'. While they might not look particularly impressive, to Erich's eye that chevron shape was an immediate clue to something that's quite rare to find in the fossil record: it's a classic example of the marks left on bone by shark teeth. We know what a modern shark bite looks like from observing modern sharks and their prey, and the marks on this bone look just like the sorts of marks a modern shark bite makes. In the next photo, Erich is re-enacting the way a shark's tooth would make this sort of mark, (though obviously when a shark bites there are many more teeth involved).

Shark tooth and whale bone Erich demonstrates how a shark tooth probably struck the whale bone.
Source: Museum Victoria
 

While it's not absolutely conclusive evidence – this sort of palaeo-behaviour trace fossil rarely is – this, and other marks on other bones from the same specimen, is enough for us to be fairly certain that this whale was bitten by a shark. We also know that this happened very close to the whale's death because the bone shows no sign of healing. This tells us that either the whale was killed by the shark that attacked it or that the shark was scavenging the whale carcass after it died – we can't be sure which but we know that the whale wasn't bitten and then got away.

Even with this uncertainty, though, this is more information than palaeontologists usually have about interactions between animals in the fossil record. Information modern ecologists take for granted, such as who's eating who, is extremely rare to find for fossils. Bite marks like these are one of the few ways palaeontologists have any idea of how food webs may have been constructed way back when. But what's really cool about this particular whale/shark palaeo-interaction, is that rather than just being satisfied with 'this whale was attacked by a shark' we can actually figure out who the culprit was. A lot of work has been done on the geological unit that this specimen was collected from so we know what was sharing the waters with our luckless whale. Of the list of sharks known from the same unit, only one has teeth big enough to have made these marks:

Fossil shark tooth Fossil shark tooth.
Source: Museum Victoria
 

This tooth comes from the shark Carcharocles angustidens, known from relatively abundant fossils around the stretch of coast our whale was collected from. C. angustidens is a close relative of the rather more famous Carcharocles megalodon which has the largest teeth of any known shark, living or extinct (some are over 18cm long!) You can see the sharp little serrations along the edge of the tooth which would have effectively sawed into the bone of its victim, leaving the grooves we see in the whale's bones today.

So we think that somewhere in the Late Oligocene, 24-27 million years ago, in a sea that covered what is now part of Victoria, a shark, Carcharocles angustidens, bit a Mammalodon whale and perhaps even killed it. It's amazing what we can infer from just a few scratches on bone.

Links:

MV Blog: Evolving the biggest mouth in history

Footage of tiger sharks scavenging a whale carcass in Queensland

Footage of sharks eating a blue whale alive

Maximum rate of mammal evolution

Author
by Kate C
Publish date
30 January 2012
Comments
Comments (2)

"How fast can a mammal evolve from the size of a mouse to the size of an elephant?" This question introduces a new paper published today by a group of international researchers led by Alistair Evans of Monash University, including Dr Erich Fitzgerald, Senior Curator of Vertebrate Palaeontology at MV.

The world's largest mammal by weight, the Blue Whale, is about 61 million times heavier than the world's smallest, the Etruscan Shrew. Erich and his colleagues are interested in how such a range of body sizes evolved within the mammals, particularly the rate at which such evolution occurs.

Previous investigators have calculated rates of evolution using narrowly-defined parameters, whether within a shorter time scale or within a limited taxonomic group. This study is the first to tackle the larger picture, using data from a variety of species that lived over the last 70 million years.

The researchers found that it takes a minimum of 1.6 million generations for terrestrial mammals to increase their mass 100-fold. To increase by 5,000-fold, it takes at least 10 million generations.

In contrast, the researchers found that land mammals can decrease in size more than ten times faster than the time it takes to increase to the same degree. Hypothetically, it could take 5 million generations for a species to evolve from rabbit size to elephant size, whereas in just half a million generations it could shrink back down again if selective pressures directed it thus. Smaller body mass gives a competitive advantage under certain conditions; this phenomenon, known as insular dwarfism, is seen in the now-extinct dwarf elephants that were stranded on Mediterranean islands by rising sea levels.

Elephant and rabbit Left: Children riding on Queenie, an Indian Elephant, at Melbourne Zoo in 1917 (MM 004061). Right: Rabbit, Oryctolagus cuniculus.
Image: Unknown | Alex J.
Source: Museum Victoria | Used under CC BY 2.0 from a_jo.
 

Interestingly, aquatic mammals such as whales evolved large body mass much faster than land mammals, taking about half as many generations to achieve the same scale of increase.

Says Erich, "Whales can get bigger because the water supports their bodies and so their maximum size is not limited by gravity." He explains that a huge body can also be an advantage for aquatic mammals because it loses less heat.

"There doesn't seem to be any slowing-down in evolution of maximum body size in whales. Land mammals may have reached a plateau enforced by gravity, but it's conceivable that the Blue Whale is not the largest possible whale. Nevertheless, energetic demands of feeding a body larger than that of a blue whale may mean that, in reality, the blue whale is as large as animals get."

Large land-dwelling mammals have a variety of solutions to the problem of gravity, explains Erich. "Some of the changes we see are extreme thickening of bones, changes in locomotion and major changes to organ systems." A gigantic rabbit wouldn't just be a large version of today's feral bunny; in fact, it would probably be unrecognisable as a rabbit. Fossils of an extinct giant rabbit described in 2011 show that it had a stiff spine to support its bulk, which meant it would not have been able to hop. Accordingly, we might need to rethink the way we portray the Easter Bunny.

Links:

Evans, A.R. et al. The maximum rate of mammal evolution. Proceedings of the National Academy of Sciences, published ahead of print on January 30, 2012.

Speed limits on the evolution of enormousness (Wired Science)

Science reveals the secrets of super-sized mammals (The Age)

Dr Erich Fitzgerald

How to dig for dinosaurs

Author
by Lisa
Publish date
19 December 2011
Comments
Comments (9)

Lisa works in the Public Programs Department at Melbourne Museum but also volunteers in the Palaeontology Department and has been on several fossil digs.

Have you ever wondered what it would be like to go on a dinosaur dig? Recently I went on a fossil-hunting adventure with a crew of 12 Museum Victoria staff and volunteers at a site called Eric the Red West in Cape Otway National Park.

120 million years ago this part of Australia was a river valley surrounded by forest. When the valley flooded, the remains of dinosaurs, small mammals, pterosaurs and forest plants (which became the coal that we see in the rock) were washed into the river. Eventually some of these bones, as well as those of animals such as fish and turtles that were living in the river, became covered by sand and mud. Over time the sediment became the grey sandstone that is exposed on beach today.

palaeontology fieldwork The crew heads down to the site.
Image: Lisa Nink
Source: Museum Victoria
 

When we first arrived on site we unloaded all of our gear and took it down onto the beach. Before we started any digging we prospected along the beach for fossils that were naturally exposed through weathering of the rock.

Prospecting and fossil finds Left: Lesley Kool and Mary Walters in search of fossils weathering out of the rock. | Right: Part of a dinosaur limb bone.
Image: Lisa Nink
Source: Museum Victoria
 

Next it was time to bring out the heavier equipment to remove rock and search for fossils that were still buried. We used large rock saws, small electric saws, sledgehammers and chisels to remove large chunks of the fossil-bearing rock.

tools to remove rock Travis removes sand from the rock with a shovel and Gerry removes chunks of rock with a sledge hammer and chisel.
Image: Liza Nink
Source: Museum Victoria
 

Removing fossils with tools. Left: David Pickering uses a small electric saw to delicately remove a fossil. | Right: Dr Erich Fitzgerald uses a larger rock saw to not so delicately (but precisely) remove a fossil.
Image: Lisa Nink
Source: Museum Victoria
 

When large chunks of rock have were removed and checked for fossils, the rest of the crew used smaller hammers and chisels to carefully break the rock down to sugar-cube sized pieces in search of tiny fossils.

Searching for fossils Left: David Pickering uses a hand lens to inspect a newly exposed fossil. | Right: Astrid patiently chisels away at rock in search of delicate fossils.
Image: Lisa Nink
Source: Museum Victoria
 

And we were well rewarded for our efforts:

Dr Erich Fitzgerald points to a fossil fish jaw Dr Erich Fitzgerald points to a fossil fish jaw he has just discovered in the rock.
Image: Lisa Nink
Source: Museum Victoria
 

Despite the rain and cold it was a wonderful experience. My friends and colleagues often ask me, 'doesn't it get boring breaking rocks on a beach all day?' but it never does. You never know when the next strike of your hammer and chisel may reveal a new fossil that hasn't seen the light of day for 120 million years. You never know, it may even be a completely new species.

You can see some of the fossils that have been found along Victoria's coastline in 600 Million Years: Victoria evolves at Melbourne Museum.

Links:

Dinosaur Dreaming Blog

MV Blog: Dinosaur Dreaming Dig

Infosheet: Inverloch fossil site

Resident artist Joceline Lee

Author
by Kate C
Publish date
3 October 2011
Comments
Comments (5)

Artist Joceline Lee has spent her last few Wednesdays in the basement of the Royal Exhibition Building among the palaeontologists, geologists, rocks and fossils. She is working on drawings for her first solo exhibition, Rendered Bones.

Joceline draws skeletons and anatomical forms in pen and ink which makes palaeontological specimens the ideal material for her. When I visited her at work, she was drawing an echidna skeleton that she'd selected from the collection. She was accompanied by her mentor Rob Delves, a sculptor who has worked with Joceline for seven years at Art Day South. This project is run by Arts Access Victoria in Melbourne's south-east to give artists with disabilities opportunities to develop their artwork through workshops, mentorships, collaborations and exhibitions.

  Joceline Lee and Rob Delves Joceline Lee and Rob Delves working on an echidna skeleton in the Museum Victoria Palaeontology Department.
Source: Museum Victoria
 

Rob said that when she first came to Art Day South, her drawings were intricate and very tiny. "Her linework was amazing in these little drawings and they just said 'skeletons'." He started bringing her photographs and models of animal skeletons about three years ago, and Joceline was hooked. "Then we brought in bigger things and it's grown from there." In July this year, MV's Discovery Program visited Art Day South bringing a tortoise shell, a huge model dinosaur leg, fossils and more for the artists to explore.

Joceline works slowly but steadily for hours at a time, with each drawing taking two to three weeks to complete. Rob loves her unique style of drawing. "She goes off in beautiful directions, with all this contrast... dark and fine lines."

Rendered Bones is part of the Melbourne Fringe Festival program from 4 to 9 October in the No Vacancy Project Space in the Federation Square Atrium. Be sure to visit the exhibition if you'd like to see Joceline's distinctive interpretation of fossils, bones and skeletons.

Flyer for Rendered Bones exhibition
Flyer for Rendered Bones exhibition.
Image: Arts Access Victoria
Source: Arts Access Victoria
 

Links:

Melbourne Fringe Festival: Rendered Bones

No Vacancy Gallery: Rendered Bones

Evolving the biggest mouth in history

Author
by Kate C
Publish date
17 August 2011
Comments
Comments (1)

Imagine that your face was articulated so that your jaw could split down the middle and expand sideways until the tips were out as wide as your ears. Imagine that you could move all the bones of your face... not just the soft tissue, but the bones themselves.

Sound bizarre? Alien, even? Yet this is exactly what happens every time a Blue Whale takes a gulp of water. The filter-feeding whales, otherwise known as baleen whales or mysticetes, have feeding adaptations that are unique among mammals. Their intriguing evolutionary history is the subject of Dr Erich Fitzgerald's research, and today he's published a paper that overturns a long-held belief about how the baleen whales evolved.

Blue Whale Illustration of the biggest mouth in history at work. The Blue Whale can expand its mouth to gulp huge volumes of krill-filled water.
Image: Carl Buell
Source: Museum Victoria
 

For several years, he has worked on an extraordinary 25 million-year-old species known from fossils that were found in the 1990s near Jan Juc on Victoria's west coast. Called Janjucetus, this early baleen whale predated the evolution of baleen – the hairy structure used by modern baleen whales to filter tiny crustaceans from the sea. Instead, Janjucetus had the large eyes and ferocious teeth of a hunter.

Erich Fitzgerald with Janjucetus Dr Erich Fitzgerald holding the jaws of Janjucetus with Melbourne Museum's massive Blue Whale skeleton in the background.
Image: Jon Augier
Source: Museum Victoria
 

There are two key changes in the skull that permit the filter feeding of modern whales. The first is a lower jaw that can split down the middle. In humans, the seam (or symphysis) where the two halves of the jawbone meet at our chin is fused, thus our jaws are rigid. In contrast, baleen whales have greatly elongated jawbones that do not meet in the middle. The second change is in the width of the upper jaw; baleen whales have evolved a wide mouth, allowing them to engulf massive volumes of water.

"Previously it was thought that the origins of both features were intimately linked to filter-feeding and that's what differentiated baleen whales from toothed whales and dolphins," explains Erich. His research has just overturned this theory since Janjucetus had a wide upper jaw yet its lower jaw had a tightly connected, immobile symphysis. "So, the loose symphysis is not typical of all baleen whales, it's a later innovation. The earliest baleen whales could not expand and contract their lower jaws so were anatomically incapable of filter-feeding, yet they had these wide upper jaws."

Jaws of Janjucetus The fossilised jaws of Janjucetus, clearly showing the immobile symphysis at the tip.
Image: Jon Augier
Source: Museum Victoria
 

What Erich describes is an elegant example of an exaptation, where a feature evolved to serve a particular function but was later co-opted into a new role. Erich believes that its wide jaw helped Janjucetus to suck in large singe prey items, such as squid or fish, and didn't evolve for filter-feeding at all.

Says Erich, "Charles Darwin reflected upon this in The Origin of Species. He wondered how you could go from a whale that has big teeth like Janjucetus does and catching fish and squid one at a time, to something like a modern Blue Whale that feeds en masse. This is the kind of fossil palaeontologists dream of finding because it shows a transitional form."

"It's an exciting discovery, but actually not as surprising as you might think," concludes Erich. "Evolution by natural selection implies that we should expect to find these kinds of fossils in the rocks." The next question he looks forward to answering is how whales shifted from suction feeding to filter-feeding. "I think we're really close to finding a transitional series of fossils that illuminate this."

Erich's paper about this discovery, 'Archaeocete-like jaws in a baleen whale', is published today in Biology Letters.

Links:

Video: Erich discusses whale evolution

MV News: Ferocious fossil

Dr Erich Fitzgerald

Baleen and toothed whales

Dinosaur Dreaming

Author
by Priscilla
Publish date
22 February 2011
Comments
Comments (2)

Priscilla is a Program Coordinator for Life Sciences and works on education programs at Melbourne Museum. She has been a regular dinosaur digger for over 10 years!

I'm often asked what it's like at a dinosaur dig. The romantic view most people have, fuelled by films like Jurassic Park, is that we simply sweep away the sand with a brush, use high-tech gadgets to locate the exact location of the bones, and get flown to tropical islands with Jeff Goldblum.

Over 100 years ago the first dinosaur fossil, the Cape Paterson Claw, was found on the coast of Victoria at a site known as Eagles Nest. Nothing much else was found until two young palaeontologists in the making, Tim Flannery and John Long, spent their youth searching the rocks along the coast of Victoria, eventually finding more fossil booty. Their finds have led to decades of dinosaur digs along the coast of Victoria.

From Cape Otway to Inverloch, the Cretaceous-aged sandstone rocks have been blasted, bashed and bored to reveal what life was like 120 million years ago in Victoria. Each year the work at the Dinosaur Dreaming Dig, which is a joint project between Museum Victoria and Monash University, recruits numerous volunteers who spend hours breaking rock. Over the years, the same volunteers return, making the whole experience more like a giant family gathering at Christmas. Uncle Norman, Mother Lesley, Sister Alanna, and Grandma Mary are all there. Gerry and his rock, Doris and her eggnog, Mike and his poems, Nick and his telescope, Nicole and her berry crumble are all part of the experience.

And yes, there are the dinosaur bones. Each year some 800 new bones are found and catalogued. Just like a Christmas stocking, you never know what you are going to find inside each rock – will it be the discovery that changes theories of evolution or another disappointment? Yet despite so many fruitless ‘stocking openings’, I and many others are lured back. After so many years of digging, amazing fossils have been found. Many of these incredible specimens are now on display in 600 Million Years: Victoria evolves. Hopefully, this clip gives you some insight into just how we find them...

Watch this video with a transcript

Links:

Dinosaur Dreaming: the Inverloch Fossil Site infosheet

Fossil collecting sites in Victoria infosheet

Dinosaur Walk

Dinosaur Dreaming blog

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Updates on what's happening at Melbourne Museum, the Immigration Museum, Scienceworks, the Royal Exhibition Building, and beyond.

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