MV Blog

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

By the tenth day of the annual Dinosaur Dreaming dig we had already catalogued more than 140 fossils. To know where to dig in the first place we need to understand the geology of the area because the types of rock and how they have been laid down can give us much information about the palaeoenvironment. Dr Alan Tait, Adjunct Research Fellow in the Department of Geosciences at Monash University is currently researching the sedimentology of the Flatrocks site and kindly explained its geology to me.

Today the site known as Flatrocks is a rocky beach dominated by light grey sandstone but 120 million years ago during the Cretaceous, the environment was very different. Australia was once part of a supercontinent called Gondwana which also comprised Antarctica, South America, Africa, New Zealand and India.

Much of Gondwana had broken up by the Cretaceous and a rift had started to form between Australia and Antarctic. The types of rocks and fossils we find along the coastline in Inverloch today tell us the story of the rift valley and the animals and plants that lived there.

The cliff face near the Flatrocks site. The grey mudstone is the remains of a flood plain which was on the floor of the rift valley. The layer where we find most of our fossils lies above this and at the top is massive sandstone. To the left of the mudstone you can see a fault where the rock layers have shifted dramatically from their original horizontal deposition.
Image: Lisa Nink
Source: Museum Victoria

The fossil layer itself consists of the sedimentary rocks, grey sandstone and conglomerate that were deposited during flooding of the rift valley. The conglomerate pebbles are made of clay eroded from the flood plain soils during flooding. The sandstone is grey because it contains grains of volcanic rock eroded from active volcanos some distance away and washed into the rift valley. The sediments also include the fossilised remains of dead animals, plants and trees. The time between the floods was long enough for large trees to grow, perhaps at least 100 years, and the floods were catastrophic.

“The main fossil bearing layer (under the red line) consists of grey sandstone with coal throughout it. The layer is bounded by a layer of mudstone below and massive sandstone above.
Image: Lisa Nink
Source: Museum Victoria

There are many fossilised tree stumps on the shore platform. Some of these trees lie horizontally with their fossilised roots still attached and are believed to have been knocked over by the force of the floods and washed down the river. We also find fossil leaves of ferns, gingkoes and monkey puzzle-like trees that once grew as part of a forest within the rift valley.

A fossil tree trunk. If you look closely you can even see the growth rings.
Image: Lisa Nink
Source: Museum Victoria  

The coal in the fossil layer is the remains of decomposing plants that once grew in the valley. Fossilised grains of pollen from these plants have also been found and by identifying their species, we can date the sediments surrounding them.

A nearby dyke (a long straight crack in the rocks through which magma from deep below the Earth's crust travels upwards and cools) is made up of basaltic rock, another igneous rock type. The dyke is 99.5 million years old and cuts through the grey sandstone, meaning it formed after the sedimentary rocks had been deposited. 

Dale Nelson stands upon the basaltic dyke near the Flatrocks site.
Image: Lisa Nink
Source: Museum Victoria  

We also find minerals at the site, like pyrite and calcite.

Minerals found at the fossil dig site, shown with objects often found in geologists' pockets, for scale. Left: Pyrite crystals | Right: Calcite crystals
Image: Lisa Nink
Source: Museum Victoria  

Links:

Dinosaur Dreaming blog

Infosheet: Dinosaur Dreaming - the Inverloch fossil site

Video: Dinosaur Dreaming

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

Last weekend hailed the beginning of the annual Dinosaur Dreaming dig season at Inverloch in Victoria. The crew will spend the next three weeks searching for the fossils of animals including dinosaurs, mammals, turtles, freshwater plesiosaurs, fish and pterosaurs that lived on and around the floodplain and in the forests that existed in the area 120 million years ago.

We can only access the dig site while the tide is out far enough to expose the shore platform, and before we can start hunting for fossils we need to prepare the site. First we remove the sand with shovels, which is often a bit of a smelly job due to the bits of rotting seaweed that have washed into the hole (the name we give to the part of the site which is being worked at any given time) with the tide.

Left: The crew removes sand, boulders and seaweed from on top of the rock layers. Right: John Wilkins and Dean Wright remove one of many large boulders from the dig site using a boulder extraction contraption John invented and built for us.
Image: Lisa Nink
Source: Museum Victoria  

Next we use large chisels, crowbars and large drills to remove the overlying layer of sandstone. Once we have access to the fossil layer we can begin searching.

Some of the crew use large chisels and sledgehammers to remove large chunks of the fossil layer and the rest of the crew sit further up on the shore breaking these large rocks into walnut sized pieces in search of fossils.

Left: Travis Park uses a sledgehammer and chisel to remove a large chunk of fossil-bearing rock. Right: Gerry Kool uses a much smaller hammer and chisel to break down chunks of rock in search of fossils.
Image: Lisa Nink
Source: Museum Victoria  

While the main aim of the dig is to find fossils, there is much more we can learn about the site. Dean Wright, a surveyor, and Doris Seegats-Villiers, a PhD candidate at Monash University, used a Leica Total Station to collect data which will be used to map geological features such as the different rock layers and fault lines. Dean plans to overlay this data onto a 3D map of the site he made last year and this information will assist scientists to better understand the geology of the site.

Dean Wright and Doris Seegats-Villiers taking data points which Dean will use to create a geologic map of the Flatrocks site.
Image: Lisa Nink
Source: Museum Victoria  

Some of the interesting bones we have found so far this season:

Left: A cross-section through a dinosaur limb bone. Right: A cross-section through a dinosaur toe bone.
Image: Lisa Nink
Source: Museum Victoria  

Links:

Dinosaur Dreaming blog

Infosheet: Dinosaur Dreaming - the Inverloch fossil site

Video: Dinosaur Dreaming

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.

February 12th is Charles Darwin's birthday, now celebrated at institutions around the world as Darwin Day. Darwin's work is obviously relevant to a lot of the research that goes on at Museum Victoria today, but we also have a direct link with him through some specimens housed in the Palaeontology Department.

Charles Darwin in 1854
Source: Out of copyright, via Wikipedia.  

Darwin's best-known work is The Origin of Species, and if you had to name the animals he was particularly interested in, you'd probably think finches, or perhaps tortoises. But these are just the tip of the iceberg; before, and after publishing The Origin, Darwin also published prolifically across a breadth of natural history subjects, including geology, zoology, ornithology, entomology and botany. All of this work was vital, both in developing his theory of evolution by natural selection, and in gaining him a wide and interested audience.

One of the lynchpins of Darwin's theory was homology, the sharing of characters due to common descent (meaning that if two species share a feature we assume, until we can show otherwise, that they both inherited it from their common ancestor). Much of Darwin's thinking about homology was developed through his detailed study of the humble barnacle. He published the first full treatment of barnacles in the early 1850s with four monographs on modern and fossil barnacles.

Over 100 years later in the 1960s, the then Curator of Palaeontology at Museum Victoria, Thomas Darragh, noticed that some of the specimen labels in the palaeontology collection had handwritten notes saying "Original figured by Darwin".

Specimen label written by Kranz.
Source: Museum Victoria  

Going back to Darwin's original descriptions and illustrations, Dr. Darragh confirmed that these specimens matched Darwin's material. For instance, looking at this photo of Scalpellum simplex and the original illustration, it's clear that the illustration is of this specimen – they share the same broken tip even though the figure shows the specimen free of the rock. Similarly, the other specimens are close matches to those in Darwin's monographs.

  Left: Extract of plate from Darwin's original monograph. | Right:Fossil barnacle Scalpellum simplex Darwin 1854. Scale bar = 1cm. (NMV P133334).
Image: Charles Darwin | Thomas Watson
Source: Out of copyright | Museum Victoria  

A little more investigation showed that all of the specimens Dr. Darragh had found had been declared lost by Thomas Henry Withers in the 1930s when he compiled a catalogue of the barnacle material at the Natural History Museum in London (then the Natural History section of the British Museum). So the specimens that had been thought lost for over 30 years were now found, but how had they come to be in Melbourne instead of London?

In 1854 when his work on barnacles was complete, Darwin donated all the material that he had collected himself to the British Museum, where, 80 years later, Withers made his catalogue. However, Darwin also borrowed from other collectors. One of these was John Morris, a mollusc specialist possibly best known for The Catalogue of British Fossils and who went on to become professor of Geology at University College London. When he donated his own collection, Darwin returned Morris' material to him. Morris later sold his collection to the German fossil dealer, August Krantz who, for some reason, discarded all of the original labels and re-wrote them.

In 1863, Frederick McCoy, the first director of Museum Victoria (then known as the National Museum of History and Geology) bought a collection of fossils from Krantz for the museum.

This was just one of many purchases of fossils and minerals that McCoy made from Krantz, but this one happened to include at least part of Morris' collection, including the barnacles that Darwin had worked on. Since nobody was actively working on barnacles, it took 100 years for anyone to realise the importance of these specimens, but since we did the specimens have been housed safely in the museum's type collection accessible for researchers around the world.

Happy Darwin Day!

Links:

Darwin Online Project 

Darwin's barnacle studies (Darwin Online Project)

Invertebrate Palaeontology Collections

Infosheet: How do barnacles cement themselves to rocks?

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.

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.
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).

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.
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

"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.

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

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.

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.

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.

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  

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.

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 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