The Lyme Regis Fossil Festival

Last month my report on the Lyme Regis Fossil Festival was published in The Palaeontological Association’s quarterly newsletter (Newsletter 89, page 97: http://cdn.palass.org/publications/newsletter/number_89/pdf/number89.pdf).  The Palaeontological Association is a leading learned society in the field of palaeontology.  It runs conferences, publishes palaeontological work, and funds trips and research.  The newsletter has information on events, short reports and research summaries, and is freely available on the PalAss website (http://www.palass.org/), along with other information such as a section advertising postgraduate opportunities in palaeontology. 

Step into the PalAss time machine, a one way ticket to fun, facts, and learning!

In May this year, the Palaeontological Association ran an outreach stall at the 10th annual Lyme Regis Fossil Festival. This wasn’t the first time that PalAss had attended the event, but it was my first time as a PalAss outreach volunteer at the Festival, and what a wonderful celebration of fossils and palaeontology it is! The Lyme Regis Fossil Festival operates as a completely free, and open-to-all, outreach festival. Numerous Earth and life science departments from universities across the UK, as well as natural history museums and scientific associations, had representatives ready to engage with the public about palaeontology. The Natural History Museum, London, had the largest presence at the Festival, with an impressive number of stalls showcasing everything from a huge Baryonyx skull, to sifting sand for tiny shark teeth. Plymouth University were getting kids to ‘walk like a dinosaur’ with paint covered dino-wellies, the University of Southampton were offering a ‘dig for fossils’ activity, and Oxford University Museum of Natural History were showcasing local Lyme Regis fossils from their collections. Along the back of the marquee situated on the Lyme Regis beach, local collectors were displaying and selling their impressive fossil finds, just as Mary Anning once did along that very beach more than 150 years before them. It is a festival of passion, discovery and intrigue for everyone involved; volunteer and visitor alike.

The PalAss outreach activity was designed as a voyage back in time. Four time periods were chosen to represent different environments and ecosystems through time; the Silurian, the Carboniferous, the Jurassic, and the Pleistocene. Each of these time periods had an associated reconstruction, painted by the talented palaeoartist James McKay. Also displayed were a selection of each period’s most iconic and abundant fossil fauna and flora. The oldest time period represented was the Silurian and the diorama depicted a warm, shallow sea, with reef-building corals, trilobites, eurypterids, orthoceras, and crinoids, all of which were present as fossil specimens. The Carboniferous focused on the plant life that dominated during this time period, as well as the large insects and creepy crawlies; Carboniferous fern fossils were also displayed. The Jurassic section dove into a 150 million year old marine setting, when ichthyosaurs and plesiosaurs ruled the oceans, and ammonites were abundant. Many of the ichthyosaur, fish, and ammonite fossils on display for the Jurassic were found in local Lower Lias rocks. The final and youngest time period represented on the PalAss stall was the Last Glacial Maximum, or ‘Ice Age’. This diorama showed classic Ice Age animals such as mammoths and cave lions against a snowy backdrop. A fossil mammoth tooth and an ox skull were among the fossils displayed.

Edine Pape speaking to school children about palaeontology and fossils.

Edine Pape speaking to school children about palaeontology and fossils.

The Festival kicked off for PalAss with Caroline Butler and Lucy McCobb from Amgueddfa Cymru – National Museum Wales visiting Thomas Hardye School in Dorchester. Although the activities took place in this school, groups of pupils from other schools in the area also attended, meaning their activities reached a large number of students in one day. The second day was similar to the first in that our outreach was aimed at school groups, but by now the whole team had arrived in Lyme Regis, and we had set up in the festival marquee. We ran the activity several times for different schools, starting with a discussion about what a fossil is and what a palaeontologist does. We then told them that we were going to take them in a time machine, back to four different periods in Earth’s history. We took them around the different sections of the stall, and described what Earth may have been like during each different time period. We asked them if they could identify any of the fossils displayed, and encouraged them to handle and explore them, before explaining what they were. Finally, we rounded off the activity by asking the students which time period they would most like to visit; the Ice Age was the clear winner!

Over the weekend, the Festival opened to members of the public, and the PalAss team was joined by James McKay. James spent his time at the Festival painting ‘mix and match’ prehistoric beasts for children, and giving these creatures scientific names. These paintings drew a lot of attention, and while the children waited for them, we were able to engage with them about palaeontology and real extinct animals, as well as showing them round our stall. On the Sunday, James Witts was interviewed by a local radio station, Abbey 104, for their ‘Local World’ programme. He spoke about the activities that we were doing at the Festival, and the importance of fossils when trying to understand Earth history.

James McKay painting mythical beasts for children at the Festival.

James McKay painting mythical beasts for
children at the Festival.

Outreach is a crucial part of science. As an academic community, we owe it to the public, as well as to future generations of scientists, to communicate our ongoing research clearly and effectively. Fiona Gill, the PalAss outreach officer, Caroline Butler, the education officer, and Liam Herringshaw, the publicity officer, do an excellent and extremely important job in organising outreach activities such as this at various festivals and events across the country on behalf of PalAss. I hope that events such as the Lyme Regis Fossil Festival can go some way toward encouraging the next generation of palaeontologists and spreading enthusiasm for natural sciences in general. So whether you are in a position to volunteer, or you are passionate about palaeontology and want to find out more, get yourselves down to future Lyme Regis Fossil Festivals; I can guarantee a fantastic, fun-filled and highly educational weekend.

The PalAss Lyme Regis 2015 outreach team (from left to right): James McKay, Gemma Benevento, Tim Palmer, Lucy McCobb, Edine Pape, Fiona Gill, James Witts, Caroline Buttler and Jo Hall.

The PalAss Lyme Regis 2015 outreach team (from left to right): James McKay,
Gemma Benevento, Tim Palmer, Lucy McCobb, Edine Pape, Fiona Gill, James Witts,
Caroline Buttler and Jo Hall.

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Messel: a Window into the Past

For the last two weeks I have been lucky enough to work with some of the fantastic mammal fossils from Messel in two German museums; the Senckenberg in Frankfurt, and the Hessisches Landesmuseum Darmstadt.  The Messel fossils are exceptionally preserved and incredible specimens, which are even more breath-taking up close, and so I thought I would write a bit about them.

The Geology of Grube Messel

‘Die Grube Messel’, or the Messel Pit, is a site in the small German town of Messel, near Frankfurt, where 47 million year old lake sediments have been preserved, and along with it many incredible fossils.  The geology of this lake is not a straightforward one, and for years was poorly understood.  It’s now thought that the lake formed atop a maar volcano vent.  The maar was created when magma rose up along faults which had formed earlier in this regions geological history, and reacted with the groundwater to cause explosive eruptions.  Over time the eruptions subsided and left a relatively shallow crater known as a maar.  Water was able to build up, and the Messel lake was formed [1].

A maar volcano vent after eruptions have subsided and a lake has formed. Image credit: [1]

The lake was a good habitat for many Eocene creatures, but it was cut off from any rivers.  This meant that, as algae, plant, and animal material in the lake decayed, oxygen was removed from its bottom waters.  The detritus formed an organic rich layer, which was completely uninhabitable.  This anoxic layer is of great importance today, and is known as the Messel oil shale.  The Messel oil shale preserves an entire ecosystem of plants and animals from the Eocene.  It is truly a window into the past.  The fossils are often complete, articulated, and have even the finest of details preserved.  This is partially thanks to the fine grained nature of the oil shale, and because the lake waters were calm and did not transport the fossils, but also because the anoxic environment meant that the organisms weren’t scavenged or disturbed by bioturbation (mixing of the sediment by burrowing animals).

Messel fossils.Top Left: Propalaeotherium. Top Right: Palaeoxhiropteryx tupaiodon. Bottom Left: Leptictidium nasutum. (Hessisches Landesmuseum Darmstadt, Display). Bottom Right: Palaeoxhiropteryx tupaiodon. (Hessisches Landesmuseum Darmstadt, Collections). Image Credit: Photographed by me.

The oil shale that the fossils are preserved in is around 40% water, meaning the fossils start to flake and crumble within hours of excavation if they are not properly prepared. The fossils are prepared out so that they are half out of the slab, and then they are set face down in resin. The underside is then prepared right down to the resin, leaving only the fossil in its new matrix substitute. Top Left: Diplocynodon dawini. Top Right: Allaeochelys crassesculpta. Bottom Left: Diplocynodon deponiae. Bottom Right: Messelophis ermannorum. (Hessisches Landesmuseum Darmstadt, Display). Image Credit: Photographed by me.

Top Left: Eopelobates wagneri. (Hessisches Landesmuseum Darmstadt, Display). Top Middle: Leaf Beetle. Top Right: Messelornis cristata. (Hessisches Landesmuseum Darmstadt, Display). Bottom Left: Atractosteus messelensis. (Hessisches Landesmuseum Darmstadt, Display). Image Credit for Top Left, Top Right, Bottom Left: Photographed by me. Image Credit for Top Middle: http://www.wired.com/2011/09/beetle-fossil-colors.

With such exquisite fossils palaeontologists have been able to reconstruct a picture of life in Eocene Messel; both the habitat and the animals that thrived there.

 An Eocene Ecosystem

The Eocene was a warm period in Earth’s history, and the climate and habitat of what is now Messel would have somewhat resembled today’s tropical rain forests.  The lake would have been surrounded by heavily forested areas, and animals were living in the lake, in the trees, and on the forest floor.

Some of the non-mammalian animals (we’ll get to the mammals, don’t worry!) that lived here include the turtle Allaeochelys, which represents a transition from the hard shell to a soft shell, the giant flightless bird Gastornis (pictured above chasing one of the smaller mammals Leptictidium), and six genera of crocodile.

The Eocene Messel Lake, surrounded by birds, mammals, and reptiles. Image Credit: Esther van Hulsen.

The Messel treetops. Image Credit: Esther van Hulsen.

Macrocranion and Asiatosuchus lakeside. Image Credit: ©2009-2015 dustdevil.

Gastornis chases Leptictidium. Image Credit: Esther van Hulsen.

The Messel Mammals

As I’ve been working with the mammals from this incredible deposit, it’s only right that this blog would be slightly biased by them.  The Eocene period marks the final stages of an adaptive radiation of mammals.  Since the extinction of the non-avian dinosaurs 65 million years ago, mammals had been evolving into numerous different ecological niches, and by the Eocene, most modern niches were represented.  Messel preserved a huge range of mammal genera and species, and below I introduce some of the most iconic and intriguing.

Leptictidium

There are three species of Leptictidium found in the Messel oil shale.  They were medium sized mammals, growing up to 90cm long including their tail, and lived on the forest floor.  They had a long snout and tail, as well as extremely long and powerful back legs, especially when compared to their front legs which were much smaller.  This has led palaeontologist and palaeoartists to reconstruct Leptictidium much like a modern day kangaroo or walaby, and place them into the small group of bipdal mammals.  Research into their locomotion is, however, ongoing, as it’s not clear whether they were fully bipedal and jumped much like kangaroos, or whether they spent more time on four legs.  Fossil remains of this animal have been found with stomach content, revealing that they ate a varied diet of insects, lizards, and plants.

Artist’s impression of Leptictidium. Image Credit: http://thezt2roundtable.com/topic/9425988/1.

Pholidocercus

The genus Pholidocerrcus is monospecific, meaning that there is only one species assigned to this genus; Pholidocercus hassiacusPholidocercus hassiacus is a relative of the modern hedgehog, and had a covering of bristles across its body much like hedgehogs do.  In addition to its spines, however, it also had scales on its tail and atop its head, making it look like it was wearing a helmet! It probably fed primarily on insects, and would have scurried around the forest floor in search for them.

Pholidocercus hassiacus. Image Credit: [2].

Pholidocercus hassiacus fossil. Image Credit: Houston Museum of Natural Sciences.

Kopidodon

Kopidodon macrognathus (another monospecific genus) was a squirrel-like mammal, living a primarily arboreal lifestyle.  This creature was a lot bigger than modern squirrels however, reaching over a meter long including its large bushy tail (seen as a black imprint around the tail bones in the image below!).  Kopidodon was most likely omnivorous, as it had large canines, but also broad molars designed to grind up plant material.

Kopidodon reconstruction. Image Credit: https://de.wikipedia.org/wiki/Kopidodon.

Kopidodon macrognathus. (Senckenberg Museum, Display). Image Credit: Photographed by me.

Palaeochiropteryx

Palaeoxhiropteryx is one of the four genera of bat found in the Messel pit, and it encompases two of the eight species within these genera; Palaeochiropteryx tupaiodon, and Palaeochiropteryx spiegeli. By the Eocene, bats were almost indistinguishable from their modern relatives in appearance.  Palaeochiropteryx was extremely abundant, making up three quarters of all of the bats found in Messel.  It was a relatively small genera, with a wing span of up to 30cm and weighing around 15 grams.  With so many bats living in the same forest, there must have been niche partitioning going on in the skies above Eocene Messel.  An analysis of the bat genera present in Messel showed that these bats were partitioning their hunting territories.  Palaeoxhiropteryx had broad wings and a low wing loading ratio (wing loading = body mass/wing area), suggesting it was a slow, manoeuvrable flyer.  Others had higher wing loading ratios and narrower wings, suggesting they were faster flyers and moved in more open spaces above the canopy (see image) [2].

Palaeoxhiropteryx (along with the other Messel bats) was an insectivore.  It would have probably had an intermediate hunting style, both picking insects off of plants and also catching them on the wing in the lower canopy area.

Palaeoxhiropteryx tupaiodon catching insects off of the Messel lake surface. Image Credit: http://www.paleospot.com/galerie_rubrique.php?rub=7.

Propalaeotherium

Propalaeotherium was an early horse relative that was about the size of a medium-sized dog.  Instead of hooves it had small ‘hooflets’, three on its back feet and four on its front.  They lived among the forest and ate a diet of plants, fruit, and berries that had fallen from the surrounding trees.

Propalaeotherium in the forest. Image Credit: http://allgeo.geologie.uni-halle.de/geiseltalmuseum/?lang=en.

Eomanis

Eomanis is the earliest known pangolin.  It was covered in scales, bar its bare underbelly, legs, and tail.  Its front limbs were adapted for digging, and its stomach content revealed that this anchient pangolin was eating a mixture of plants and insects [2].  This suggests that pangolins may have started out with a more herbivorous diet, and specialised to feed almost exclusively on ants as they evolved.

Eomanis. Image Credit: [2].

Buxolestes

Buxolestes has been likened to modern day otters for a variety of reasons.  It had a long robust tail, as do modern otters which helps to propel them through the water whilst swimming.  Buxolestes also had well developed hind legs, again to aid with swimming, suggesting that this animal was spending a significant amount of time in and around the water.  This animal was a pescivore, and fish bones have been found in its stomach in exceptionally preserved fossils [2].

Buxolestes. Image Credit: [2].

Darwinius

Darwinius masillae is known from a single fossil, a juvenile female that has been lovingly named Ida.  Ida is an incredibly important fossil, as she represents a link between the prosimian primate lineage; the lemurs, lorisoids and the extinct adapiformes, and the simian lineage; the higher primates, including, of course, us! Darwinius masillae is a link in our own ancestral tree, and places the timing of this split during the Eocene.

For many years after Ida was first discovered, she sat in a private collectors house, admired only as a piece of art.  She was found in 1983 and her real importance was hidden from the world for over twenty years.  We can be grateful that this particular collector knew how to preserve the Messel fossils using resin, meaning that the fossil didn’t crumble.  This is another case that highlights how important it is for fossils to make their way to the scientific community; incredibly important discoveries may be hidden away behind closed doors.

Ida. Image Credit: © Atlantic Productions Ltd.

Ida sleeping, with nocturnal Messel mammals foraging and hunting around her. Image Credit: Esther van Hulsen.

Ida. Image Credit: Esther van Hulsen.

Thank You’s

I would like to thank Thomas Lehmann and Elvera Brahm at the Senckenberg and Norbert Micklich at the Hessisches Landesmuseum Darmstadt for agreeing to my collections visit and looking after me during my stay. It was a very successful first collections visit!

Bibliography

  1. Gruber, G., Micklich, Messel. Treasures of the Eocene. Hessisches Landesmuseum Darmstadt. (2007).
  2. Rose, K.D., The Beginning of the Age of Mammals. The Johns Hopkins University Press. (2006).

The Top 10 Palaeobiology Breakthroughs of 2014 (as chosen by me)

So, we made it through 2014.  I would say that it’s been a long year, but as I get older that becomes less and less true, and the years seem to fly by before I know it.  For me though, 2014 has been a great year.  A year of change, and a year of realising some of my biggest dreams.  2014 will always be the year that I was offered a place at Oxford to study for my DPhil.  As any academic should know, finding funding was not an easy task, and I had waited so long for this opportunity; I couldn’t be happier to be back in academia!  So what has happened in this field I love so much in the last 12 months? What’s new in Palaeontology?

With every passing year palaeobiology becomes an ever more exciting area of science to work in, and this last year has been no exception.  From dissecting permafrost mammoths, to the ‘golden age of dinosaur discovery’, 2014 has kept us on our toes from start to finish! These are my top 10 breakthroughs in palaeobiology of 2014 (in date order):

  1. Evidence That Placental Mammals Originated Before the K-Pg

The year got off to a controversial start in January, with a paper [1] that disagreed with previous work [2] on the timings of origins for placental mammals.  O’Leary et al [2] argued for an early Cenozoic origin of placentals, based on fossil occurrence dates, while dos Reis et al found that combining fossil and molecular data places their origin in the Cretaceous, pre-dating the Cretaceous-Palaeogene (K-Pg) extinction event.   The second study [1] disagrees with the first [2] because the authors felt it was misguided to use only fossil data in their analysis, as the fossil record is fundamentally biased by sampling.  Many people think that fossil occurrences should be used only as an upper age bound for molecular clock analyses because the record is too biased to be used in any other way.  It is true that the fossil record is biased by preservation potential and sampling, and this should always be taken into account when using raw fossil occurrence dates, but it is hard to know just how unreliable it is (one thing we should bear in mind is that it only takes one fossil occurrence to push a lineage origination date back in time). This difference in results between the two studies isn’t only important for researchers looking at mammal evolution across the K-Pg (as I am!), but also for the wider palaeontological community.  As we move forward, we must work toward reconciling the different time estimations given by fossil and molecular data, and aim to use both to constrain a reliable date for the evolution of many animal lineages.

Image 1: Examples of modern placental mammals (Credit: Edited from http://biology4isc.weebly.com/uploads/9/0/8/0/9080078/642909929.jpg)

Image 1: Examples of modern placental mammals (Credit: Edited from http://biology4isc.weebly.com/uploads/9/0/8/0/9080078/642909929.jpg)

Please see *doi:10.1098/rsbl.2013.1003* and *doi:10.1126/science.1229237* for more information.

  1. New Cambrian Fossil Site Uncovered

February saw the discovery of a new site of wonderfully preserved Cambrian fossils (see images 2-5) [3].  The site lies in Canada’s Marble Canyon, and is part of the same Burges Shale Formation that yielded over 200 species more than 100 years ago.  In just two weeks the team had found 15 new species, giving us yet more insight into this exciting and extraordinary point in evolutionary history.  I look forward to hearing more about these animals in the following years.

Image 2: Leanchoilid from Canada's Marble Canyon. (Credit: Robert Gaines, see also http://www.livescience.com/43264-gallery-amazing-cambrian-fossils-from-canada.html)

Image 2: Leanchoilid from Canada’s Marble Canyon. (Credit: Robert Gaines, see also http://www.livescience.com/43264-gallery-amazing-cambrian-fossils-from-canada.html)

Image 3: Marrella splendens (Credit: Robert Gaines, see also http://www.livescience.com/43264-gallery-amazing-cambrian-fossils-from-canada.html)

Image 3: Marrella splendens (Credit: Robert Gaines, see also http://www.livescience.com/43264-gallery-amazing-cambrian-fossils-from-canada.html)

Image 4: A polychaete worm fossil from the Marble Canyon site in Kootenay National Park (Credit: Jean-Bernard Caron, see also http://www.livescience.com/43264-gallery-amazing-cambrian-fossils-from-canada.html)

Image 4: A polychaete worm fossil from the Marble Canyon site in Kootenay National Park (Credit: Jean-Bernard Caron, see also http://www.livescience.com/43264-gallery-amazing-cambrian-fossils-from-canada.html)

Image 5: A double rainbow breaks above the researchers' field camp in Kootenay National Park. (Credit: Jean-Bernard Caron, see also http://www.livescience.com/43264-gallery-amazing-cambrian-fossils-from-canada.html)

Image 5: A double rainbow breaks above the researchers’ field camp in Kootenay National Park. (Credit: Jean-Bernard Caron, see also http://www.livescience.com/43264-gallery-amazing-cambrian-fossils-from-canada.html)

Please see *doi:10.1038/ncomms4210* for more information.

  1. Finding The First Jaws

In June, a primitive fossil fish, found close to the Marble Canyon site explained above, was described and published in Nature [4].  This fossil is Cambrian in age, and sheds light on some of the earliest evolutionary steps toward gnathostomes, or ‘jawed vertebrates’.  The organism, named Metaspriggina (see image 6), has been phylogenetically placed as a stem vertebrate as it possesses a wide range of vertebrate features such as ‘a notochord, a pair of prominent camera-type eyes, paired nasal sacs, possible cranium and arcualia, W-shaped myomeres, and a post-anal tail’ [4].  Metaspriggina also has gill arches preserved.  The first of these structures, located closest to the head, are the structure that later evolved to form the jaws in vertebrates.  This is the first time these structures have been observed so early in the fossil record, and for that reason Metaspriggina makes it into my top 10 list!

Image 6: Left: Illustration of Metaspriggina swimming. Right: Fossil of Metasprigina from Marble Canyon – head to the left with two eyes, and branchial arches at the top. (Credit: Drawing by Marianne Collins. © Conway Morris and Caron. Photo by Jean-Bernard Caron © ROM. See also http://www.cam.ac.uk/research/news/new-fossil-find-pinpoints-the-origin-of-jaws-in-vertebrates)

Image 6: Left: Illustration of Metaspriggina swimming. Right: Fossil of Metasprigina from Marble Canyon – head to the left with two eyes, and branchial arches at the top. (Credit: Drawing by Marianne Collins. © Conway Morris and Caron. Photo by Jean-Bernard Caron © ROM. See also http://www.cam.ac.uk/research/news/new-fossil-find-pinpoints-the-origin-of-jaws-in-vertebrates)

Please see *doi:10.1038/nature13414* for more information.

  1. Early Skeletal Animals Built Reefs

Reef-building is an important step in the history of life on Earth.  It is an example of co-operative behavior between organisms, where individuals can gain protection and ‘enhance feeding efficiency’ [5].  In June of 2014, a paper demonstrated that reef-building was practiced among the earliest skeletal animals [5].  These animals were called Cloudina (see image 7), and they cemented themselves to one another to form reef structures.  These Cloudina reefs were found in Namibia, and are 548 million years old, a whole 7 million years older than reefs previously assumed to be the oldest examples.This find suggests that skeletal animals began building reefs prior to the Cambrian explosion, an event that was, until now, thought to have driven reef-building behavior. This could suggest that organisms were responding to ecological pressures such as predation even in the Precambrian!

Please see *doi:10.1126/science.1253393* for more information.

  1. Feathers Found on an Ornithischian Dinosaur

For years, people have been debating whether feathers were an ancestral or derived trait within the dinosaur clade.  Late in 2013, palaeontologists suggested that scales were most likely to be the ancestral trait for dinosaurs, and that feathers must have evolved later [6].  Many scientists believed that feathers evolved in the Theropod lineage, but were not present in the Ornithischia or Sauropodomorpha clades.  Up until now, filamentous structures found on Ornithischia dinosaurs have been widely debated but in July of 2014, an Ornithischian dinosaur from the Jurassic of Siberia was found with both scales and feathers [7].  The animal, Kulindadromeus zabaikalicus, has both monofilaments and more complex featherlike structures across its body (see artists impression, image 8).  This discovery shows that feathers and scales were present simultaneously in early dinosaurs, and gives new support for the theory that feathers were widespread among all dinosaur clades.

Image 8:  Artists impression of Kulindadromeus zabaikalicus in its lacustrine environment. (Credit: Andrey Atuchin. See also http://www.bristol.ac.uk/news/2014/july/fossils-found-in-siberia-suggest-all-dinosaurs-had-feathers.html)

Image 8: Artists impression of Kulindadromeus zabaikalicus in its lacustrine environment. (Credit: Andrey Atuchin. See also http://www.bristol.ac.uk/news/2014/july/fossils-found-in-siberia-suggest-all-dinosaurs-had-feathers.html)

Please see *doi:10.1126/science.1253351* for more information.

  1. Miniaturisation Was the Key to Survival For Dinosaur Descendants

Non-avian dinosaurs are today completely extinct.  They were wiped out during the K-Pg extinction ~66 million years ago.  However dinosaurs do still live among us today! Unlike their extinct predecessors, birds made it through the K-Pg boundary to become the most specious of all tetrapods alive today [8].  So why were they able to survive, when the previously hugely successful non-avian dinosaurs didn’t make it through?  It now appears that the avian bird lineage was the only branch of the dinosaur tree where dinosaurs continued to get smaller over 50 million years [9].  An earlier 2014 study [8] also found that it was only in the dinosaur lineage leading to birds, that high rates of evolution were sustained for a long time, and therefore the lineage was able to repeatedly exploit new niches through time.  Their small size may have allowed them to continue to radiate into new niches and this could have given birds the edge when life on Earth faced the most recent of its major mass extinctions [8,9].

Image 9: Artists impression of the Dinosaur-Bird transition. (Credit: Davide Bonnadonna, see also http://www.bbc.co.uk/nature/28563682)

Image 9: Artists impression of the Dinosaur-Bird transition. (Credit: Davide Bonnadonna, see also http://www.bbc.co.uk/nature/28563682)

Please see *doi:10.1126/science.1252243* and *doi:10.1371/journal.pbio.1001853* for more information.

  1. 59-tonnes and still growing; a gigantic titanosaur uncovered in Argentina

In September, a huge titanosaur dinosaur was discovered in south-western Patagonia, Argentina [10].  The animal is from the Late Cretaceous, (-84-66ma), and has been named Dreadnoughtus schrani, after the battleships, because of its enormous size.  This titanosaur is one of the most complete of the largest sauropodomorphs ever discovered, with up to 45.3% of bones, and 70.4% of the postcranial elements recovered (see image 10), allowing estimations of its body mass to be calculated.  This individual has been estimated at a staggering 59.3 metric tonnes (see artists impression, image 11)! Although this is currently the largest estimation for any sauropodomorph, scientists can’t say for certain whether D.schrani is the largest due to the fragmented nature of other gigantic titanosaur remains.  Moreover, experts think that this huge animal was still growing at the time of death.  For me, this find is not only important as a candidate for the largest dinosaur, but because if it is, then it is also the largest animal ever to have walked the Earth.  With such a high percentage of the postcranial bones preserved, Dreadnoughtus gives us a fantastic opportunity to investigate the biomechanics and anatomical structures involved in supporting such an incredibly massive terrestrial organism.

Image 10: Diagram showing Dreadnoughtus size compared to a human.  White bones indicate recovered fossils. (Credit: http://www.abc.net.au/news/2014-09-05/worlds-biggest-dinosaur-dreadnoughtus-schrani/5722108)

Image 10: Diagram showing Dreadnoughtus size compared to a human. White bones indicate recovered fossils. (Credit: http://www.abc.net.au/news/2014-09-05/worlds-biggest-dinosaur-dreadnoughtus-schrani/5722108)

Image 11: Artists impression of Dreadnoughtus. (Credit: Jennifer Hall, see also http://newsblog.drexel.edu/2014/09/04/dreadnoughtus-schrani-frequently-asked-questions-on-the-super-massive-dinosaur/)

Image 11: Artists impression of Dreadnoughtus. (Credit: Jennifer Hall, see also http://newsblog.drexel.edu/2014/09/04/dreadnoughtus-schrani-frequently-asked-questions-on-the-super-massive-dinosaur/)

Please see *doi:10.1038/srep06196* for more information.

  1. Ichthyosaurs Missing Link?

Ichthyopterygians are marine reptiles that lived during the Mesozoic period.  They are secondarily marine, meaning they evolved from a terrestrial ancestor, but sadly, as with so many of the important evolutionary links in the fossil record, there were no examples of any intermediate organisms.  In November, however, a fossil was found in China that dated to ~248Ma [11] and appeared to be a basal ichthyosauriform (see image 12).  The animal is much smaller than ichthyopterygians, and parts of its anatomy point toward an amphibious lifestyle, making it an excellent candidate for an intermediate organism between a terrestrial tetrapod group and  ichthyopterygians.  It has large flippers for its size, meaning it was likely able to support itself on land, moving around in a way similar to modern-day seals!  Its short, wide snout and thickened ribs suggest that, unlike ichthyopterygians, it was probably a suction feeder.  It’s always exciting to find intermediate species in the fossil record, and their discovery, although infrequent, can tell us huge amounts about the processes of evolution.  This is especially true when these animals underwent a major transition like the one from terrestrial to marine, or vice versa, and therefore this discovery easily makes my top 10 breakthroughs of 2014.

Image 12: Fossil of amphibious basal ichthyosauriform. (Credit: reference [11])

Image 12: Fossil of amphibious basal ichthyosauriform. (Credit: reference [11])

Please see *doi:10.1038/nature13866* for more information.

  1. Mammoth Autopsy

In November, what has to be my favourite palaeontology story of 2014 occurred.  A permafrost mammoth found on Maly Lyakhovsky Island in northern Siberia was dissected by an international team of scientists, including Dr Tori Herridge from the London NHM.  Carbon dating pinpoints the mammoths age to ~40,000Ma.  The mammoth, found in May of 2013 and lovingly named ‘Buttercup’ (see image 13), was exceptionally well preserved, and presented mammoth experts with this exciting and incredibly rare opportunity.  Although I cannot deny the excitement any palaeontologist gets from finding a beautifully preserved fossil, I assure you, you would not find any researcher in our field that would turn down the opportunity to have the unfossilised carcase of any extinct organism.  Although this might sound goary, many more evolutionary questions can be answered when the complete biology of an animal is available as opposed to fossilised remains.

Image 13: Buttercup being removed from the tundra. (Credit: Semyon Grigoriev/Northeastern Federal University in Yakutsk, see also http://www.livescience.com/48768-photos-mammoth-autopsy.html)

Image 13: Buttercup being removed from the tundra. (Credit: Semyon Grigoriev/Northeastern Federal University in Yakutsk, see also http://www.livescience.com/48768-photos-mammoth-autopsy.html)

The team were able to dissect Buttercup over three days as her body thawed out (see image 14), and during the process deduced some interesting things about her life.  Buttercups tusks revealed that she was a female, and that she had 8 calf’s.  Pebbles were also found in her gut, around the size of a ping-pong ball, which, due to an abnormality with her teeth, were thought to have been used to grind up food and aid digestion.  The scientists were even able to suggest a cause of death for Buttercup.  They believe that she became stuck in a peat bog and died from predation.

Dr Tori Herridge with Buttercup during the dissection. (Credit: Nick Clarke Powell, See also http://www.cbc.ca/news/technology/woolly-mammoth-autopsy-provides-flesh-and-blood-samples-1.2849875)

Image 14: Dr Tori Herridge with Buttercup during the dissection. (Credit: Nick Clarke Powell, See also http://www.cbc.ca/news/technology/woolly-mammoth-autopsy-provides-flesh-and-blood-samples-1.2849875)

Maybe the most astonishing thing to come from this mammoth autopsy however, is the presence of liquid blood (see image 15).  Scientists managed to collect some of Buttercups blood as she thawed, and many believe that this is our first step toward mammoth cloning.  The ethics behind this idea are, however, heavily debated, and I must admit it is not a venture that I personally support.

Image 15: Roy Weber, a researcher at Aarhus University, Denmark, holds up a vial of Buttercup's blood. (Credit: Renegade Pictures, see also http://www.livescience.com/48768-photos-mammoth-autopsy.html)

Image 15: Roy Weber, a researcher at Aarhus University, Denmark, holds up a vial of Buttercup’s blood. (Credit: Renegade Pictures, see also http://www.livescience.com/48768-photos-mammoth-autopsy.html)

  1. Dating the Deccan Traps

For decades, there has been debate as to whether the formation of the Deccan Traps, a mountain range in India made up of layers of basalt from a massive outpouring of lava (see image 16), coincides with the K-Pg extinction, and with it the extinction of the dinosaurs.  The Deccan Traps have long since been suggested as a possible contributing factor, or even cause, of the K-Pg mass extinction, but dating the flood basalts has proved difficult.  For a long time the Deccan Traps were thought to have occurred before the extinction, and, although theories were put forward for a gradual decline of species prior to the K-Pg, the impact theory remained the most accepted one.  In December however, a new paper appeared in science [12] proclaiming new dates for these huge lava outpourings.  Using uranium-led (U-Pb) dating, the researchers obtained dates that suggested that the Deccan Traps were active just ~250,000 years before the Chicxulub impact, and that 80-90% of the ~123,000 cubic miles of lava was erupted within ~750,000, straddling the extinction event itself.  If these dates are correct, they provide evidence that these flood basalts could have contributed to the extinction that wiped out all non-avian dinosaurs, along with many other creatures that were on Earth 66 million years ago.  Flood basalts in different areas have also been suggested as possible causes of other major extinction events, for example the Siberian Traps and the End-Permian mass extinction [13].  If it is in fact true that the Deccan Traps coincide with the K-Pg, then it shows that such an event can cause a large extinction, and gives reason for the other flood basalts around the globe to be re-dated.

Image 16: The Deccan Traps. (Credit: http://green98.tumblr.com/)

Image 16: The Deccan Traps. (Credit: http://green98.tumblr.com/)

Please see *doi:10.1126/science.aaa0118* for more information.

Bibliography

1. dos Reis, M., Donoghue, P.C.J., 7 Yang, Z., Neither phylogenomic nor palaeontological data support a Palaeogene origin of placental mammals. Biol. Lett. 10(20131003) (2014).
2. O’Leary, et al., The Placental Mammal Ancestor and the Post-K-Pg Radiation of Placentals. Science. 339(6120) 662-227 (2013).
3. Caron, J-B., Gaines, R.R., Aria, C., Mangano, M.G., & Streng, M., A new phllopod bed-like assemblage from the Burgess Shale of the Canadian Rockies. Nat. Com. 5(3210) (2014).
4. Conway Morris, S., & Caron, J-B., A primitive fish from the Cambrian of North America. Nature. 512, 419-422 (2014).
5. Penny, A.M., Wood, R., Curtis, A., Bowyer. F., Tostevin, R., & Hoffman, K-H., Ediacaran metazoan reefs from the Nama Group, Namibia. Science. 344(1504) 1504-1506 (2014).
6. Kaplan, M., Feathers were the exception rather than the rule for dinosaurs. Nature News. (2013) doi:10.1038/nature.2013.14379.
7. Godefroit, P., Sinitsa, S.M., Dhouailly, D., Bolotsky, Y.L., Sizov, A.V., McNamara, M.E., Benton, M.J., & Spagna, P., A Jurassic ornithischian dinosaur from Siberia with both feathers and scales. Science. 345(6195) 451-455 (2014).
8. Benson, R.B.J., Campione, N.E., Carrano, M.T., Mannion, P.D., Sullivan, C., Upchurch, P., & Evans, D.C., Rates of Dinosaur Body Mass Evolution Indicate 170 Million Years of Sustained Ecological Innovation on the Avian Stem Lineage. PLoS Biol. 12(6) (2014).
9. Lee, M.S.Y., Cau, A., Naish, D., & Dyke, G.J., Sustained miniaturization and anatomical innovation in the dinosaurian ancestors of birds. Science. 345(6196) 562-566 (2014).
10. Lacovara, K.J., et al., A Gigantic, Exceptionally Complete Titanosaurian Sauropod Dinosaur from South Patagonia, Argentina. Scientific Reports. 4(6196) (2014).
11. Motani, R., Jiang, D-Y., Chen, G-B., Tintori, A., Rieppel, O., Ji, C., & Huang, J-D., A basal ichthyosauriform with a short snout from the Lower Triassic of China. Nature. (2014).
12. Schoene, B., Samperton, K.M., Eddy, M.P., Keller, G., Adatte, T., Bowring, S.A., Khadri, S.F.R., & Gertsch., B., U-Pb geochronology of the Deccan Traps and relation to the end-Cretaceous mass extinction. Science. (2014).
13. Burgess, S.D., Bowring, S., & Shen, S-Z., High-precision timeline for Earth’s most severe extinction. PNAS. 111(9) 3316-3321 (2014).

Plate Tectonics, Subducting Slabs, and Nature Papers

I’ve mentioned before in this blog that the Earth is made up of continental and oceanic plates.  At convergent plate margins, less buoyant oceanic plates are subducted beneath the continental plates, and drawn down into the mantle.  Although the mantle is often depicted as convecting molten lava, it is actually solid rock.  The reason that the solid rock in the mantle is able to convect however, is due to the immense stress that it is subjected to over huge periods of geological time.

The way a slab behaves once it begins its descent into the mantle is poorly understood.  The only evidence we have of the shape of these subducted slabs at depth is from seismic imaging1, where the colder, more rigid slab is visible amid the hot, convecting mantle.  These images, however, are often difficult to interpret.  Moreover, they only offer us a snapshot in time, while tectonic processes span unimaginably long geologic timescales.  For this reason scientists often disagree on the angle of trajectory for the descending oceanic plate.

A Case Study

Image 1: Slab wall imaged underneath North America (Credit: Sigloch; http://www.geophysik.uni-muenchen.de/Members/sigloch (see also ref. 2)).

As North America moved westward after the initial breakup of Pangea2 ~200 million years ago, the Panthalassa Ocean to its west began to close.  For many years, geologists believed that the Farallon plate that lay beneath the Panthalassa Ocean, was subducted eastwards into a trench at the western edge of North America.  In an exciting new paper, however, geologists Dr Karin Sigloch and Dr Mitchell Mihalynuk have proposed a new theory for the history of the slab that lies beneath North America.  After analysing high resolution topographic images of the slab (see image 1), they found that its horizontal cross-sectional shape did not match the contours of the western coast of North America.  Moreover, the slab is a massive 400-600km across, 4-6 times thicker than would be expected from a single sheet of subducting lithosphere3 .  The plate appears to have been subducted at a close to vertical angle, and so there became a need to explain its unexpected thickness.  The vertical appearance of the subducted plate further contradicted a westward-moving trench along the west coast of North America.  There also appears to be a second phase of subduction, a younger (shallower) section of slab wall which lays further west, and connects up to present day subduction under North America.

One way in which the geologists were able to explain these phenomena was by the presence of a volcanic arc system within the Panthalassa Ocean (the ocean that existed to the west of North America at this time).  If there had been a string of island arcs, the Farallon slab could have subducted to the west, into a stationary trench along the archipelago (see image 2).  This would explain the discontinuity between the shape of the subducted slab wall and the shape of the west coast of North America.  Once the Panthalassa Ocean that lay to the east of the archipelago-associated trench had closed, North America would have collided with the island arcs, and a ‘polarity switch’ would have occurred.  Now, the remaining ocean that lay to the west of the arcs would be subducted to the east, underneath North America.

Image 2: (a) Westward subduction and slab pile-up under volcanic arc, (b) collision of North America with the volcanic arc, and closure of the ocean that lay east of the arc system, (c) polarity-shift in subduction, and subduction of the remaining ocean in an easterly direction (Credit: Reference 1).

Image 2: (a) Westward subduction and slab pile-up under volcanic arc, (b) collision of North America with the volcanic arc, and closure of the ocean that lay east of the arc system, (c) polarity-shift in subduction, and subduction of the remaining ocean in an easterly direction (Credit: Reference 1).

An explanation for the huge width of the slab was also proposed in this paper, and has far-reaching implications for future studies of slab dynamics.  As already discussed above, the mantle flows.  At approximately 670 km, there is a viscosity4 jump within the mantle, where the mantle below is much more viscous than above.  The theory here is that the subducting slab moves relatively easily through the less viscous upper mantle, but begins to buckle and fold onto itself as it reaches this boundary.  There may even be a period of time where the slab is not dense enough to continue its descent into the lower mantle, and would therefore have to ‘wait’ at the boundary until there is enough material to allow the slab to pass through into this higher viscosity environment.

Please follow this link *doi:10.1038/nature12019* to read more about this exciting new theory!

1Seismic imaging distinguishes between the cold rigid slab and the hot convecting mantle by the speed at which the P-waves travel through it.  P-waves are able to travel faster through colder, denser material.

2Pangea was a supercontinent that formed ~300 million years ago during the Late Palaeozoic, and existed for just over 100 million years, before it began to break up during the Mesozoic.

3Lithosphere comprises the Earth’s crust, and some of the uppermost mantle.

4Viscosity is the extent to which a substance resists uniform flow.  For example, honey is more viscous than water.

Bibliography

  1. Sigloch, K., & Mihalynuk, M.G., Intra-oceanic subduction shaped the assembly of Cordilleran North America. Nature. 496. 50-57 (2013) (doi:10.1038/nature12019).
  2. Sigloch, K., McQuarrie, N., & Nolet, G. Two-stage subduction history under North America inferred from multiple-frequency tomography, Nature Geoscience, 1, 458 – 462 (2008) (doi:10.1038/ngeo231).

Earthquakes Breaking Boundaries

One of the first things you are taught at school about earthquakes, and volcanoes for that matter, is that they occur on or around plate boundaries.  This is not the whole story in either case, but today I will be talking about earthquakes.  Earthquakes that happen within the centre of a plate, or ‘intraplate earthquakes’.

So, what is an earthquake?  Earthquakes occur when a fault within the Earth’s surface suddenly slips, and causes shaking around an epicentre.  The shaking is the result of a release in energy that had been held as tension within the plate prior to the fault rupture.

Capture

Image 1; (a) – Australia’s position on the Indo-Australian Plate, and the positions of seismic activity on and around the plate. The plate boundary is clearly picked out by the majority of the recorded earthquakes. (b) – Australian earthquakes, 1900-2009. (Image Credit: AIR – http://www.air-worldwide.com/Publications/AIR-Currents/An-Unexpected-Catastrophe–Anniversary-of-the-1989-Newcastle-Earthquake/)

Like I said, not all earthquakes occur along plate boundaries – however most do (see image 1(a) – the plate boundaries are clearly picked out by the cluster of earthquakes). Earthquakes occur at plate boundaries because, for the most part, plates are more rigid internally, and weaker and more susceptible to deformation along their boundaries. As the plates are transported around the Earth’s surface (on a geological time scale) by plate tectonics, the interior of the plates does not deform as readily as their margins. At divergent plate boundaries (areas where two plates are moving away from each other), many shallow earthquakes tend to occur, and at convergent plate boundaries (areas where plates are colliding) intermediate to deep earthquakes are most common [1].

Sometimes, however, it is possible to have a ‘weak spot’ within a plate.  Although the rigid plate model is a good ‘general rule’, everyone knows general rules don’t produce ground-breaking science.  Again and again, geologists are coming across awkward tectonic settings within plates that just don’t conform to the conventional rigid plate model.  Image 1(a) and 1(b) show the number of intraplate earthquakes that have occurred in Australia, which lies within the centre of the Indo-Australian plate.  The deformation within plates is much slower than at plate margins, accounting for much of the differences in frequency between inter- and intraplate earthquakes.

Image 2: Black arrows showing the different directions of tension within western Europe. (Image credit: Reference [2])

Image 2 is an example the deformation that can occur within a plate.  Tensional and compressional stresses can build up, as the direction of strain varies across a plate.  This can cause faults and fracture zones, leading to earthquakes.  As with the western Europe example seen in image 2, it is often possible to identify areas of a plate which are all moving in the same direction.  These areas are now seen as smaller, rigid blocks, also deforming around their exterior.

The take-home message of this article is to remind the reader to use caution when considering ‘general overarching rules’ in science.  Simple models often don’t explain the whole story.  The rigid plate model, in its simplest form, is not able to be used as an explanation for intraplate seismicity.  The true state of our Earth’s plate interactions is a much more complex and interesting one, and one worth taking the time to understand in a little more detail.

References

  1. Hamblin, W.K., Christiansen, E.H. Earth’s Dynamic Systems (10th ed). Pearson Education. Inc. (2004).
  2. Tesauro, M., Hollenstein, C., Egli, R., Geiger, A., Kahle, H.G. Continuous GPS and broad-scale deformation across the Rhine Graben and the Alps. Int J Earth Sci. 94. 525-537 (2005).

Evidence For Evolution In Everything We Do

Co-operation for mutual benefit within humans is commonplace (even if it may not always seem that way in our conflict-ridden world).  The explanation for this seems an easy one, we are a conscious species, able to make sensible predictions about our surroundings, and able to use language to communicate.  We can predict the benefits of working together and therefore can use our intellect to form mutually beneficial relationships.  Co-operation between species for mutual benefit, or ‘mutualism’, however, is also observed and even frequent in many other species alive today.

Mutualism is one of the more straightforward evolutionary interactions to explain.  Of the four possible outcomes of inter- or intra-species interaction, mutualism is the only one which results in increased fitness in both the actor and recipient.  The only other behavior that increases fitness in the actor is selfishness, behavior that is beneficial to the actor but detrimental to the recipient, for example parasitism.  The other two interactions result in reduced fitness in the actor.  Altruism reduces fitness in the actor but increases it in the recipient, and spite reduces fitness in both parties [1, 2].  At first, these last two relationships seem to be counter-productive when viewed in the setting of natural selection, but are easier to explain when thought about in conjunction with kin selection.  Altruism may occur when the actor acts to benefit closely related kin, and in turn increase the chances of genetically similar DNA being passed on.  Spite is more rare, but may work in a similar way.  The actor may act to lower the fitness of a distantly related individual in a chance that closely related kin may have an advantage.  In both cases, the benefits to the chances of genetic propagation must outweigh the personal cost [3].

Sea turtle surrounded by 'cleaner fish' eating the algea from its shell (Image credit: Doug Perrine/Seapics/Solent)

Sea turtle surrounded by ‘cleaner fish’ eating the algea from its shell (Image credit: Doug Perrine/Seapics/Solent)

One such mutualistic relationship that has occurred in nature is the symbiotic relationship between sea turtles and cleaner fish.  Of course there are many examples I could have chosen to talk about, but I’ve chosen this example because I am extremely fond of turtles.  A fondness that was only reinforced this year while holidaying in Turkey.  I knew that I would have to be very lucky indeed to come across a Loggerhead turtle in the wild, but with their nesting sites nearby I kept my hopes up.  Imagine my delight, then, when I saw not only one but dozens in their natural habitat while on a boat trip.  What an amazing sight.  Things were to get better still. A few days later we saw one that had come right up to the harbor side, presumably waiting to be fed by off-cuts thrown in by the local fishermen.  I sat and watch him for hours, swimming back and forth less than a meter away from me.  My family had long tired of watching and had gone to find themselves some ice cream in a nearby bar, but I was transfixed.  As I watched, mesmerized by this beautiful creature, I realised that as he turned, every so often, a small grey fish would slip out from under him, before quickly realigning itself underneath the turtle.  My turtle had a cleaner fish!

The relationship between sea turtles and cleaner fish is a relatively simple, but nonetheless interesting, one.  Throughout their lives, sea turtles shells and bodies can become covered algae and ectoparasites.  The cleaner fish can feed off of this algae, the parasites and possibly even dead skin from the turtles body.  This situation is mutually beneficial for both the fish and the turtle.  The turtle gets a free cleaning service, and the fish an easy meal [4] (see image).  It has been documented that, in some species, the fish feeding on the ectoparasites have become specialized to feed only on this food source.  In some cases, cleaner fish congregate in ‘cleaning stations’, where the turtles can come to be scrubbed and rejuvenated after a long day at sea.  The sea turtles have been observed approaching these cleaning stations and adopting a solicitation pose, signalling to the fish that it’s time to clean their way to an easy meal [5].

Bibliography

  1. Hamilton, W.D., The genetical evolution of social behaviour, I & II. J. Theor. Biol. 7, 1-52 (1964)
  2. Hamilton, W.D., Selfish and spiteful behaviour in an evolutionary model. Nature. 228, 1218-1220 (1970)
  3. West, S.A., Griffin, A.S., Gardner, A., Social semantics: altruism, cooperation, mutualism, strong reciprocity and group selection. Journal Compilation European Society For Evolutionary Biology. 20, 415-432 (2007)
  4. Losey, G.S., Balazs, G.H., Privitera, L.A., Cleaning symbiosis between the wrasse, Thalassoma duperry, and the green turtle, Chelonia mydas. Copeia. 3, 684-690 (1994)
  5. Schofield, G., Katselidis, K.A., Dimopoulos, P., Pantis, J.D., Hays, G.C., Behaviour analysis of the loggerhead sea turtle Caretta caretta from direct in-water observation. Endang. Species. Res. 2, 71-79 (2006)

Can We Leopards Ever Really Change Our Spots?

For around two weeks now, we have been undergoing our cohort based cross-training within the area of Environmental Science.  Our learning is roughly divided into three streams, ‘Biodiversity, Ecology, and Evolutionary Processes’, ‘The Dynamic Earth, Surface Processes, and Natural Hazards’, and ‘The Physical Climate System’.  We all come to this Doctoral training course, a new initiative by NERC with the aim of making us more readily able to collaborate and contribute to other subjects, with our own in-depth and greatly honed knowledge within one of these three areas.  But how important is this training, do we really need to know about all those ‘other’ subjects?

Many different disciplines coming together to study the Earth

Many different disciplines coming together to study the Earth

At the start of this week, we were asked to identify the ‘critical moments in Earth history’.  As I sat and listened to the answers offered up by my newly acquired peers, I began to realise how completely consumed we are by our own, somewhat narrow, subject areas.  Although our subjects overlap in often very intricate ways, the answers we gave as individuals conformed remarkably with our own background. To give a few examples, the Geologists felt that the critical moments were linked with planet Earth itself, the separation of the core and mantle, the onset of plate tectonics, the Palaeontologists suggested the Cambrian explosion and the big five mass extinctions were most important, and the Ecologists believed that the industrial revolution, and the start of agriculture would change the world forever.  As we shouted out our suggestions on this topic, our lecturer commented that he felt he could begin to see which subject areas we were studying, and he could not have been more right!

So to what extent does our interest and passion for a subject control the importance we place on it.  Of course, the answer is ‘an awful lot’!  As if it was not obvious enough from my previous example, the point was really hammered home in our ‘Biodiversity, Ecology, and Evolution’ seminar just a few days later.  These seminars are a little different from our usual cross-training classes, as everyone attending them should consider themselves, at least in some way, a Biologist. Within these Biology sessions, we discuss all manner of Biological processes and theories, and it is interesting to see how each one of us brings it back to our own background knowledge and subject area almost every time.  The Ecologists asking how they can apply this phenomena to conservation efforts, the Palaeontologists asking if this can be detected in the fossil record, and so on.

On a more serious level, it is obvious that in some cases, different groups of us (in the case of our latest discussion on Phenotypic Plasticity*, the Palaeontologists (I among them)), are too ready to dismiss these theories because they lie so far outside our own work, and therefore we have a limited and often incomplete understanding of the processes.

So back to my original question. Can we really change our spots? Can we begin to embrace and understand other areas of our own Science? I am certain that the answer to that question is ‘yes’!  I have already begun to see glimpses of it happening as we discuss relevant theories among ourselves and share our subject-based knowledge.  In the aforementioned Biology session, after a coherent and engaging explanation of Phenotypic Plasticity delivered by a Biologist with more ‘conventional’ training in the subject, other members of the group were slowly beginning to see potential for this previously misunderstood theory where they hadn’t before.

Overall, what I am trying to say, is that this cross-training may well be even more important than we had originally thought.  It appears not only to be opening our eyes to other closely linked subjects, but may more importantly be making us stronger and more inclusive in our own narrower fields, providing us with all the building blocks we will need to become excellent researchers in the future.

*’Phenotypic Plasticity’ is the ability of an organism to change its phenotype based on it’s environment.

The Rain That’s Shaping the Earth

It is today widely accepted that tectonic processes across the globe can affect climate in many ways.  Any Earth scientist worth their salt will have penned at least one essay on that famous example, the formation of the Tibetan plateau.  Here, the uplifted plateau has driven climatic changes, and in particular has affected the intensity of the Asian monsoons to its East, and increased aridity to the West [1,2].  It is less well understood, however, how weathering and climate systems may affect the tectonic processes themselves.  I, at least, have made it through an undergraduate geology degree without being introduced to this phenomena, and it was only in a graduate level seminar last week that I heard about it for the first time.

The Science

First some context.  During a mountain building period, or ‘orogeny’, continental tectonic plates begin to collide, due to continental drift.  The two plates are thrust towards each other after the closure of an ocean due to the subduction of the more dense oceanic plate, and a mountain range begins to form.  As the continents converge, a fold and thrust belt forms where the rock begins to bend and fracture under the pressure of the driving forces of mantle convection [3].  These thrust belts form wedges, and this wedge will continue to deform until a critical taper is reached, at which point the entire wedge is able to move forward along a basal thrust fault.  Now here’s where it gets interesting.  The amount of deformation needed to produce this critical taper is, among other things, controlled by the combination of rock types within the wedge itself, but now it seems it can also be affected by weathering of the upper surface of the wedge.   Erosion across the surface of the wedge can affect a mountain range in a number of ways, including its width, rock uplift rate, its structure (see diagram), and the distribution of metamorphic facies.  Mountain ranges even appear to exhibit different patterns of uplift across their length due to asymmetries in the amount of rainfall on different parts of the tapering wedge.   This uplift response to erosion can be attributed to an isostatic rebalancing, as mountains extend deep underneath themselves, displacing the mantle [4, 5, 6].  This theory allows climate to be a driving factor in the way in which orogenic belts deform and behave, and has implications for how Earth scientists should interpret mountain belt geology. I for one, hope to see this entering undergraduate geology syllabuses across the world.

Differing wedge deformation and structural styles due to different amounts of erosion. (Taken from [6])

Differing wedge deformation and structural styles due to different amounts of erosion. (Taken from [6])

Life Lessons

So what can we take from this brave and exciting new theory?  It is a chance for environmental and Earth system scientists to recognise that geologic processes cannot be handled in isolation.  As the very wise man, Richard Feynman, once said; ‘Nature uses only the longest threads to weave her patterns, so each small piece of her fabric reveals the organisation of the entire tapestry’.  Each process and phenomena we see on Earth is both dependent upon, and depended on by, other natural processes.  This is an invaluable lesson to learn when working as a scientific researcher.

Perhaps more importantly however, are the implications of new theories such as this for all academics.  The presenter of our seminar, Professor Bruce Levell, admitted that very few geologists would have dared suggest that short term processes such as climate could affect something as long-lived and powerful as tectonics even a mere decade ago .  This should never again be the case in science.  Have we not learnt from our past? Many of the most innovative and far-reaching ideas that have shaped our understanding of science today were smirked at and whispered about when first proposed, Darwin’s theory of evolution by natural selection,  Galileo’s suggestion that the Earth orbits the Sun, and Wegener’s theory of continental drift as recently as a century ago are examples of but a few.  It shows us that, as researchers,  we should not be afraid to think outside the box, and challenge old and accepted viewpoints.  No-one should ever shy away from the possibility of having  their name added to the list of great scholars who overturned widely held opinions and changed their respective fields forever.

Bibliography

  1. Zhisheng, A., Kutzbach, J.E., Prell, W.L., Porter, S.C. Evolution of Asian monsoons and phased uplift of the Himalaya-Tibetan plateau since Late Miocene times. Nature. 411, 62-66 (2001).
  2. Duan, A., Wu, G., Liu, Y., Ma, Y., Zhao, P. Weather and Climate Effects of the Tibetan Plateau. Adv. Atmos. Sci. 29, 978-992 (2012).
  3. Doyle, P., Bennett., M.R., Baxter, A.N. The Key To Earth History. John Wiley & Son. (1994)
  4. Stockmal, G.S. Modeling of large-scale accretionary wedge deformation. J. Geophys. Res. 88, 8271-8287 (1983).
  5. Whipple, K.X. The influence of climate on the tectonic evolution of mountain belts. Nat. Geoscience. 2, 97-104 (2009)
  6. Simpson, G.D.H. Modelling interactions between fold-thrust belt deformation, foreland flexure and surface mass transport. Basin Res. 18, 125-143 (2006)