Revising echinoderm relationships based on new fossil interpretations

A re-interpretation of the ambulacral system of Eumorphocystis (Blastozoa, Echinodermata) and its bearing on the evolution of early crinoids

by: Sarah L. Sheffield and Colin D. Sumrall
Summarized by Sarah Sheffield

What data were used? New echinoderm fossils found in Oklahoma, USA, along with other fossil species of echinoderms. The new fossils had unusual features preserved.

Methods: This study used an evolutionary (phylogenetic) analysis of a range of echinoderm species, to determine evolutionary relationships of large groups of echinoderms.

The arms of Eumorphocystis. A. This is an up close image of the arms that branch off the body. B. The arms of Eumorphocystis have three separate pieces comprising them: these three pieces are highlighted in yellow, blue, and green. This arm structure is nearly identical to early crinoid arms, indicating that crinoids might be more closely related to creatures like Eumorphocystis than we previously thought.
Results: Eumorphocystis is a fossil echinoderm (the group that contains sea stars) that belongs to the Blastozoa group within Echinodermata. However, it has unusual features that make it unlike any other known blastozoan: it has arms that extend off of the body, which is something we see in another group of echinoderms, called crinoids. Further, these arms have a very similar type of arrangement to the crinoids: the arms have three distinct pieces to them (see figure). Researchers placed data concerning the features of these arms, and the rest of the fossils’ features, into computer programs and determined likely evolutionary relationships from the data. The results indicate that Eumorphocystis is closely related to crinoids and could indicate that crinoids share common ancestry with blastozoans.

Why is this study important? This study indicates that our understanding of the big relationships within Echinodermata need to be revised. Without an accurate understanding of these evolutionary relationships, we can’t begin to understand how these organisms actually changed through time-what patterns they showed moving across the world, how these organisms responded to climate change through time, or even why these organisms eventually went extinct.

The big picture: This study shows that crinoids could actually belong within Blastozoa, which could change a lot of what we currently understand about the echinoderm tree of life. Overall, this study could help us understand how different body plan evolved in Echinodermata and how these large groups within Echinodermata are actually related to one another. Data from this study can be used in the future to start to understand evolutionary trends in echinoderms.

Citation: Sheffield, S.L., Sumrall, C.D., 2018, A re-interpretation of the ambulacral system of Eumorphocystis (Blastozoa, Echinodermata) and its bearing on the evolution of early crinoids: Palaeontology, p. 1-11. https://doi.org/10.1111/pala.12396

To read more about Diploporitans please click here to read a recent post by Sarah on Palaeontology[online].

Kevin Jiménez-Lara, Paleomammalogist and Paleobiogeographer

Kevin taking photographs of a fossil anteater skull deposited at the fossil mammal collections at the Field Museum in Chicago, IL.

First, let me introduce myself. I am a Colombian PhD student at the National University of La Plata, Argentina. My research is focused on the evolution of xenartrans, mammals that include armadillos, sloths, and anteaters.

Since I was a child, I have had a strong fascination to learn about nature. For that reason, I loved (and I still do love) reading a lot and watching documentaries about science, wildlife, meteorological phenomena, the history of the Earth, the history of the Universe, astrophysical theories and hypotheses, and other similar topics. Science has an amazing explanatory power, and that has always been what I like most about it. Science allows us to know our place in the Universe.

Following my vocation, I studied biology in college. Although during my undergrad there were many disciplines that caught my attention, the only one that enamored me was the study of extinct life forms, i.e. paleobiology. At first glance, it is not easy to explain why I wanted to be a paleobiologist, since there are very few Colombian paleobiologists and institutions that teach paleobiology and/or develop paleobiological research in my home country. However, studying the unique history of evolution of living beings seemed not only a noble, respectable activity, but it also became a passion that I believe will always accompany me as long as I live. Paleobiology has formed the basis of my life in the professional field, and also in a personal, philosophical sense.

Kevin doing paleontological prospecting and fossil collection in the La Venta area of southwestern Colombia. In this area some of the most important fossil assemblages of tropical continental vertebrates can be found.

To perform research in paleobiology in a country located in the intertropical belt of the planet (near the equator) and characterized as one of the most biologically diverse areas on Earth poses great challenges and opportunities. On the one hand, there is little or no state support to study paleobiology as a consequence of socio-historical development. In addition, there are limitations related to logistics in regions that are difficult to access due their geographic location and/or security features. We also face scarcity of continuous outcrops of sedimentary rocks where fossils can be found. Often, as a result of climatic factors and abundant vegetation (plant life), fossils are poorly preserved (however, sometimes, they are exquisitely preserved!). But these limitations are largely compensated by huge opportunities. Fossils from the tropics are exceptionally valuable. They document innumerable evolutionary stories that can help explain one of the most disturbing questions for many biologists: why is there a tendency in different groups of living organisms to present greater diversity in the intertropical zone compared to other regions on Earth, such as in higher latitudes?

Paleobiology in the tropics is very necessary because of the generalized geographic bias in research of many extinct organisms and periods of Earth’s history. Namely, most research on these topics has been conducted in Europe and North America. In Colombia, paleontological field expeditions and studies have yielded surprising findings, including, of course, our flagship fossil organism (in my opinion): Titanoboa (Titanoboa cerrejonensis). For all those who do not know it, this snake lived approximately 60 million years ago in the extreme north of Colombia (Guajira peninsula), and its most surprising feature is its size and body mass. Titanoboa measured about 13 meters in length and could exceed one metric ton in weight. That makes it the largest known snake of all time!

Artists’ rendition of Titanoboa in its natural habitat, a very warm and humid tropical forest in La Guajira, northern Colombia, around 60 million years ago. Other reptiles of this time period were also giants, such as crocodiles and turtles.  Image by Jason Bourque.

I contribute to tropical paleobiology by studying fossil xenartrans (armadillos, sloths, and anteaters), particularly those that lived in northern South America and southern Central America. I seek to clarify questions on evolutionary/phylogenetic relationships between extinct representatives of these charismatic mammals and, at the same time, to reconstruct historic changes in their geographical distributions (where they lived through time).

Why is it important to study extinct armadillos, sloths, and anteaters? There are many reasons, but my favorite is that they are animals whose origin and evolution are closely related to great-magnitude abiotic (non-biological) events and processes (such as climate changes and tectonic events). Through tens of millions of years, abiotic factors shaped their biology and ecology to configure the xenartrans in one of the most peculiar mammals that existed during the Cenozoic (the last 65 million years). Have you seen how strange some armadillos look when they roll into a ball, or the very slow movements of a three-toed sloth, or the long tubular snout of a giant anteater? If you have not seen this, you should check out the videos linked in the previous sentence. But in the fossil record we know even more bizarre features of xenartrans than we see in living species. For example, several species of giant sloths used to swim (yes, you read it right, ‘swim’) in littoral zones (areas close to the beach) of western South America around 5 million years ago! Is that not mind-bending?

Several species of the giant sloth genus Thalassocnus could swim in shallow marine habitats off the west coast of South America (Peru and Chile) during the late Miocene-Pliocene (7-4 million years ago). Paleobiologists know this primarily from studies on anatomical adaptations to swimming indicated from the animal’s bone structure. Image by Roman Uchytel.

Xenartrans constitute an outstanding study model on how Earth and life evolve together, from their evolutionary differentiation ~98 million years ago, possibly triggered by the geographic separation of Africa and South America, until their colonization of North America during the last 9 million years in the environmental framework of the Panama Isthmus uplift and the Last Great Glaciation. This makes xenartrans interesting organisms to study evolutionary patterns and processes of high complexity in the tropics.

I am particularly interested on the evolutionary implications (diversification) of dispersal (or movement) events of xenartrans from northern South America to North America (including its ancient Central American peninsula) during geologic intervals which immediately precede the definitive formation of the Isthmus of Panama. Long distance dispersal through a shallow sea, like that which existed between southern Central America and northwestern South America before the complete isthmus emergence, is one of the least understood biogeographic phenomena. The explanatory mechanism of long-distance dispersal allows for disjunct distributions and for us to more comprehensively understand the subtle interaction between distinctive faunas of contiguous areas.

In order to fulfill my general research objective, it is necessary to work hard in determining identities and affinities of Middle-Miocene to Pliocene (15-2 million years old) xenartrans of the aforementioned regions, including not only previously collected fossils, but also new findings. In a complementary way, it is required to put identifications in geographic context through faunal similarity/dissimilarity methods. I also use probabilistic biogeographic models (models that use statistics) to infer major distributional patterns and processes of several subgroups of xenartrans, so that we could understand in an analytic, non-strictly traditional narrative way, the changes of their occurrences in space. Finally, long distance dispersal events through poorly suitable environments for most xenartrans, like shallow seas, are approached through locomotive reconstructions to estimate dispersal capacity (vagility).

I want to end this post by giving an important advice to all those who aspire to be scientists. The path to work in science may be, to a greater or lesser extent, long and complex. However, if you remain true to your convictions and strive under a regime of self-discipline, you will not only be a scientist, but also one of the most prominent researchers in your field. Question everything, do not firmly hold onto hypothesis that have little associated evidence. And, above all, write, write to clarify in your mind many issues related to your research.

To learn more about Kevin and his research, check out his blog called ‘Caribe Prehistorico’. To find this post in Spanish, head to Kevin’s blog by clicking here.

Can you dig it?

Rose here –

In the geology gallery at the museum, scientists explore their own research and help visitors better understand the process of fossilization. Photo from @EPS_UTK on Twitter.

At the University of Tennessee in Knoxville, we have a natural history museum on campus called the McClung Museum of Natural History and Culture. Every year they do a family fun day event called Can You Dig It? where scientists from different departments on campus come and set up various activities to engage families. The Earth and Planetary Sciences department always shows up with several fun activities for families and kids of all ages. This year we had quite a few things going on.

Outside we had two tables of planetary activities. One table was talking about volcanoes and how to tell the difference between rocks formed by volcanic eruptions and rocks formed by meteorite impacts. We had real meteorites and impact deposits, as well as some volcanic rocks, so the kids could hold them all and really see the difference.

Other graduate students outside with experiments dealing with impact craters for visitors to explore!

I was at the other planetary table, where we had some more meteorites and 3D-printed models of actual impact craters on the moon and Mars. We used these to explain how the shape of impact craters change depending on the size of a meteorite and the speed at which it impacts. We also had a tub of flour with a thin layer of cocoa powder on top. There were several marbles and small balls, and kids could hold one above the tub and drop it to make their very own impact crater. The layering using cocoa powder allowed us to show them how ejecta blankets work at real impact craters. An ejecta blanket is made of rocks from the impact site being blown up and out of the crater and landing to form a “blanket” surrounding the crater. In the tub, you could see flour on top of the cocoa powder after the impact, showing how buried layers get exposed at the surface surrounding impact craters.

Graduate students have a STEAM (Science, Technology, Engineering, Arts, and Mathematics) for students and visitors to get more information about a variety of topics. Photo from @EPS_UTK on Twitter.

Inside the museum, we had a table where people could bring in rocks or fossils they had collected and geologists or paleontologists would help identify them. This is a really popular thing, and some people bring loads of rocks they’ve been collecting all year.
If you have a local museum, make sure to go check them out. Local museums are often cheap or free and also host fun events like this one!

Dipa Desai, Paleoclimatologist & Educator

Dipa working in Colorado with the National Park Service.

What do you do?

I am a paleoclimatologist, and I study the ecological and environmental effects of climate change using the fossil record. Specifically, I research how the Ross Ice Shelf in West Antarctica responded to temperature and atmospheric CO2 concentrations slightly higher than what Earth will experience in the next several decades. The Ross Ice Shelf is currently the largest mass of floating ice in the world, and West Antarctica is currently melting faster than the rest of the Antarctic Ice Sheet–what’s going to happen when this much ice melts into the ocean? How will melting affect regional plankton communities, the base of marine food webs? When that much freshwater is added to the ocean, what happens to ocean currents and circulation? I’m interested in answering these questions and using research outcomes to improve environmental policies and climate change mitigation strategies.

I’m also an educator! I spent the last two years in the classroom teaching 5th and 6th grade STEM (Science, Technology, Engineering, Mathematics) classes, and I informally teach when I participate in STEM outreach events and programs. I plan to use my research as a model to teach the next generation of voters and environmental stewards about their planet’s historical and future climate change, and inspire the next generations of diverse, innovative STEM professionals. As an educator, I have seen how disparities in access to educational opportunities disproportionately affect low-income communities, communities of color, immigrants and non-native English speakers, and other traditionally oppressed and disadvantaged groups. As a member of these communities, I see a lack of representation and inclusion in STEM professions, and a gap in scientific literacy in our policymakers, so I want to use STEM education to affect greater social and political change.

What do you love about being a scientist?

I love learning about the Earth’s past–being the first person ever to see a fossil since its deposition, using clues in the fossil record to understand and imagine what the Earth looked like millions of years ago, and making connections to predict what our world will look like in the future. However, my favorite part of the job is telling other people about what I do! I can see folks light up when I mention I study fossils, and it’s cool to see how many people grew up wanting to become a paleontologist, just like me! I think most people believe paleontology doesn’t have any real-world applications but in reality, paleontology offers a unique perspective to understanding the modern environment. When I tell students, I see them get excited about science and all its possibilities: I remember when I judged the MA State Middle School Science Fair once year, a participant was amazed that you can use fossils to study climate change, and she asked what else can we study using fossils? It is exciting to share my career with youths, especially those who look like me, because their idea of what a paleontologist looks like and does changes when they meet me.

Describe your path to becoming a scientist. 

As a kid I loved dinosaurs and exploring outside, so I knew I wanted to be a paleontologist from an early age, but I wasn’t sure if I’d ever get here. Growing up as a child of undocumented immigrants, our family faced housing, food, and financial insecurities, so college seemed beyond our means. However, I received the Carolina Covenant Scholarship to become the first person in my family to attend college, and I studied Biology at the University of North Carolina at Chapel Hill (Fun Fact: Time Scavengers Collaborator Sarah Sheffield was my teaching assistant for Prehistoric Life class!). I completed a B.S. in Biology, and minors in Geological Science, Archaeology, and Chemistry.

While I was an undergraduate at a large research institution, I didn’t have a dedicated mentor or the cultural capital to know I should pursue undergraduate research as a stepping-stone to getting into graduate school. After graduation, I pursued research opportunities with the National Park Service in Colorado and the Smithsonian Tropical Research Institute in Panama, where I got the chance to conduct independent research projects, help excavate and catalog fossils, and teach local people about their community’s paleontological history. While in Panama, I became fluent in Spanish and wondered how I could use my new experiences and skills to communicate complex STEM concepts to broader audiences. I transitioned to teaching middle school for the next two years; I taught hands-on STEM classes to 5th and 6th graders in the largely immigrant community of Chelsea, Massachusetts. I enjoyed giving my students educational opportunities that will help them in the future, and the challenges my family faced in my childhood prepared me as an educator to understand how my students’ personal lives affected their learning in my classroom.

The experiences I pursued after my undergraduate career gave me the skills and clarity needed to develop and pursue a graduate research degree. I’m currently working on my Master’s/Doctoral joint degree in Geosciences at the University of Massachusetts at Amherst.

How do you communicate science? How does your science contribute to understanding climate change?

For my graduate research, I’m studying how warmer-than-present paleoclimates affected Antarctic ice cover and the paleoecology of the surrounding ocean. Specifically, I study the Miocene Climatic Optimum, when global temperatures and atmospheric carbon dioxide concentrations were slightly higher than they are today, and close to what we expect to see at the end of the century. Studying the deep sea records of this time period reveals how microfaunal communities (i.e. foraminifera) reacted to a rapidly warming global climate, and how changes in Antarctic ice cover impacted sea level and ocean circulation; this can be applied to improve climate models and future environmental policies.

I want to bring my research to public audiences through in-person, multilingual outreach at museums, schools, and other educational institutions, and through online media to make climate science accessible and improve scientific literacy. Using multimedia, interactive, and open-access platforms to communicate science not only reaches more people, but also fits the needs of many different learning populations; this is why I believe STEM disciplines need to move away from the traditional format of communicating findings in paid science journals and articles.

What is your advice for aspiring scientists?

Mistakes are the first steps to being awesome at something.

Try as many new experiences as possible.

Identify what skills you need to do the job you want, then identify opportunities that will give you those skills.

Find a career that you enjoy, you are good at, that helps others, and hopefully makes you some money along the way.

Volunteering at Amherst Regional Middle School

Dipa here-

This past December, I got the opportunity to share my research and interests in climate change with a group of curious middle schoolers at Amherst Regional Middle School in Amherst, Massachusetts!

Amherst Regional Middle School during a beautiful New England fall day.

The school partners with University of Massachusetts Amherst Graduate Women in STEM (science, technology, engineering, mathematics) organization to connect graduate researchers to middle school students through 20-minute Science SoundByte presentations. The 7th and 8th grade students get to enjoy the presentations during their lunch times and learn about a variety of STEM research. As for me, I get to practice explaining my research and sharing my interests to the next generation of researchers.

An example of a fossil ammonite that I used for my outreach with the middle schoolers.

While I was planning my presentation I knew I wanted to get these students thinking about climate change, since it is a problem that affects them too. The students talked with each other and then shared out what they knew about climate change, sea level rise, and their impacts on the environment–they knew so much! To explain how I use fossils to study climate change in the past, I gave the students marine fossils (fossil shark teeth, mollusks, ammonites, and corals) and asked them to draw the organism and its habitat. Did it live in the reef, open ocean, at the seafloor, or in the water column? If these fossils were found in the same location, what does this say about sea level over time in that place?

The students had fun getting to touch and look at fossils, and they worked together to solve how much sea level rose over time for the activity! It was great to be back in front of a class and talk to students about their interests in STEM and how we can work together to understand modern climate change.

Exploring St. Augustine, Florida

Jen here –

Outside of the Castillo de San Marcos along the beach. It’s quite an impressive and old structure!
I was recently one of fifteen participants in a workshop. Most participants in this workshop are graduate students or recent graduates studying paleontology or biology. The workshop is a month long with very few days off. We had one two day weekend and decided it would be fun to be tourists and go to St. Augustine! St. Augustine is a very old city that is on the eastern coast of Florida and is home to Castillo de San Marcos National Monument.

a close up of my hand next to the coquina that was molded into a pillar. Abby next to that same pillar for a better scale! Most of the rock used for the buildings was coquina!
We were incredibly excited to realize that much of the local stone work was sourced from local rock. This rock is called coquina. Coquina is a sedimentary rock that is made up of shell fragments! The coquina is from the Anastasia Formation that was deposited in the Late Pleistocene (around 2.5 to 0.012 million years ago). We spent a lot of time with our faces pressed into walls looking at what shelly creatures were preserved in the wall. The National Park Service has a nice write up explaining how creating the fort out of coquina was incredibly beneficial, click here to read more. Essentially, the rock did not break when the opposing forces began firing weapons and at the fort. Instead, the rock absorbed the shock and compressed when hit with cannon fire!

A group of scientists examining one of the coquina walls. This one was absolutely filled with nice sized oysters.
We spent time exploring the fort, which had an amazing amount of rooms with some extraordinary details preserved. When I say the entire fort was made of coquina, I mean the entire thing. It was one of the most incredible things I have ever seen! There were rooms with barrel vaulted ceilings, tall arch like ceilings, some with carvings in the walls, and much more.

Underneath the boardwalk at the St. Augustine beach. These pillars were filled with organisms that stick on other things for most of their lives.
After visiting the fort we spent time around the city exploring and being tourists. Then we decided to venture out to the beach. Remember, paleontologists study ancient life. This means many of us have training in biological sciences and get really excited about animal life! We got to the beach and some people hopped right into the water while others sat on the beach and read or took a walk along the beach. May and I decided to walk along the beach and we eventually came to these large pillars supporting a boardwalk.

A close up of some of the barnacles with my finger for scale! Some of them were quite large!
These pillars were completely covered in sea creatures! Mostly oysters, other small clams, snails, and barnacles! Most notably were the large barnacles that were a beautiful pink/purple color! Barnacles are related to crabs and lobsters but look so very different. It is absolutely astounding that these creatures can be cemented to the pillars and live for periods during high tide. Not all of the animals were still alive that were on the pillars, especially those that were quite high up.

This is a great example of how we can better explore the world around us through the lens of different sciences! Geology that contain biological remains and lots of living organisms on the beach!

Florida Association of Science Teachers

Jen here –

Here is a flyer from our workshop with the information for the institute that I am part of.

Part of my new job is as a postdoctoral associate at a newly developed institute: Thompson Institute for Earth Systems. This institute has a primary goal of helping translate the complex science done at the University of Florida as it relates to Floridians. This includes anything related to the environment and the primary Earth systems (life, land, water, air). Recently, the institute was awarded a large grant to pursue a project to get scientists into Florida classrooms. To help promote and share content we hosted a workshop at the annual Florida Association of Science Teachers (FAST).

My supervisor had submitted the proposal for this workshop but was also giving a lecture the day before on the larger project and suggested I run the workshop instead. The idea was to give a brief but useful content overview to the educators and then allow time for lesson plan development and questions. This was a surprisingly daunting task: I’m used to giving quick research talks on a very specific topic and here I was tasked with describing how global processes can affect Floridians.

Simplified diagram to show the processes of weathering and erosion. One of the major limiting nutrients is phosphorus, which is held within the rocks!

It took me an incredibly long amount of time to decide how I wanted to structure the talk. A colleague had suggested we play BINGO during the talk. I made BINGO cards for the teachers with terms that I would use during the content portion of the workshop. If someone got BINGO they would have to share the terms and describe how they are interconnected. One of the key points of the workshop was to exhibit how interconnected all of the spheres really are. The talk began with a direct issue here in Florida – sea level rise. NOAA has a sea level rise viewer where you can simulate what happens in a specific area when sea level rises. So I zoomed in to the area directly around where the conference was in Miami, Florida. The simulator starts at 0 and goes up to 6 feet, and unfortunately the average elevation in Florida is only just above 6 feet. I then walked the educators through the four basic spheres of Earth system and how we can visualize them here in Florida. This included how sea level rises, ocean circulation, erosion and weathering, cave and sinkhole (karst) features, greenhouse gases, and more!

The next portion of the workshop was designated to allow the teachers time to brainstorm ideas for a lesson or activity and to ask questions to content experts (the rest of our lab group and team was there in the room). There were some really great activities thought out and we were able to discuss ideas with the teachers for how we can better serve them as an academic institute. Overall, it was a great experience for me to share more information about Earth’s natural systems and foster discussions with educators.

National Fossil Day at the Florida Museum

Jen here –

Our tables are the first two on the right! It was never jam packed but there were over 1700 visitors to the museum in 5 hours!

National Fossil Day is a holiday enacted in 2010 to celebrate prehistoric life. Each year museums, institutes, and organizations plan events around understanding geology, paleontology, and Earth’s history! This year, I helped plan activities for the FOSSIL project and the department of vertebrate paleontology at the Florida Museum of Natural History. The annual event has all the natural history departments and several local organizations set up as a knowledge fair. Adults and children can wander around to different tables to learn about Florida’s different animals, plants, and more!

View of the visitors at the museum for National Fossil day!

At the FOSSIL project table, we displayed real megalodon teeth, 3D printed teeth made of plastic, and digital teeth! On the myFOSSIL website you can look through a 3D gallery (click here) and move digital fossils around in your browser. We also had an app up that was developed by the iDigFossils group to estimate body size of the sharks based on their teeth! It was really fun and helped show the utility of the website!

A close up of my sticker! #NotADinosaur! My synapsid kin!

The vertebrate paleontology table had a modern turtle shell next to ancient fossil turtle pieces! The idea was you could select a piece of shell material and try to figure out where on the turtle shell the piece was fun. This was difficult with some pieces but others were very clearly the edge of the shell or contained ribs. As many of you may know, I am not a vertebrate paleontologist so I had to quickly learn as much as I could about turtles. Shout out to my friend Jeanette for teaching me how to identify turtle shell fragments the week before the event. Many of these turtle pieces were about 5 million years old and from areas around Florida! We also had a few jaws for people to look at different teeth and then play a matching game. The game had you match different animals and teeth, then we talked with the players about diet and how we can use differently shaped teeth to think about what food the animal was eating.

The entrance to the new Permian Monsters exhibit at the Florida Museum of Natural History.

I helped out at the two tables inside but outside we had a dig pit and wash pit stations. So one was where you would dig through sand to find different fossils and the other was where you would use a screen to sieve through material to find smaller fossils!

We had our National Fossil Day celebrations a bit early to coincide with the opening of a new exhibit, ‘Permian Monsters’. The Permian period is incredibly interesting because it was before dinosaurs when mammals were dominant and roaming the Earth. I was asked to be on the radio to describe the differences between dinosaurs and mammals in less than 30 seconds! At first I was thinking… what the heck am I going to say to these people but then I knew: ‘The major difference between these early mammals and dinosaurs is the amount of holes in their heads.’ The radio host lost his mind and then asked me a million questions after we were off air.

Right in the front door of the Permian Monsters exhibit was a giant eurypterid. I immediately requested a photo.

This was my first National Fossil Day at a new institution and I had a lot of fun! I hope everyone got to celebrate and share their love and knowledge for fossils!

How Much Did Antarctic Ice Melt 8 Million Years Ago?

Minimal East Antarctic Ice Sheet retreat onto land during the past eight million years

Jeremy D. Shakun, Lee B. Corbett, Paul R. Bierman, Kristen Underwood, Donna M. Rizzo, Susan R. Zimmerman, Mark W. Caffee, Tim Naish, Nicholas R. Golledge, & Carling C. Hay

The problem: There has been debate among scientists if the East Antarctic Ice Sheet melted substantially during the Pliocene (~5.3-2.6 million years ago) and Miocene (23-5.3 million years ago) when the amount of carbon dioxide in the atmosphere was higher (and thus the global average temperatures were much warmer). Some scientists think that as the Earth was warmer during this time, the ice melted back substantially, thus exposing some land surface on East Antarctica. Other scientists think this is not possible based on other lines of evidence. This study set out to investigate whether or not the ice sheet melted back and exposed land by measuring the amount of cosmogenic nuclides, Beryllium 10 and Aluminum 26 (written as 10Be and 26Al). Both 10Be and 26Al occur in rocks that have been exposed to the sun (to read more about cosmogenic nuclides, click here).

A figure from the Shakun et al. paper. Panel A represents a map of Antarctica, with the Transantarctic Mountains represented as triangles. The location of the core used in the study is denoted by a black star. Panel B is a zoomed-in area of East Antarctica (the box in Panel A) showing the directions that ice flows from the continent. Panel C shows what East Antarctica would look like if the ice melted back enough for the location of the drill core to be exposed to sunlight.

Methods: First, the researchers of the study needed to obtain rocks and sediment that was underneath East Antarctica. Lucky for them, there was already drilled cores from this area! In 2006-2007, a team of scientists went to Antarctica for the purpose of recovering sediment cores from beneath the East Antarctic Ice Sheet. The team ended up with two cores that were more than 1,200 meters (0.75 miles) in length. The project was called ANDRILL, and you can read more about it here. The cores are stored in a special facility, and any scientist that wants material (rocks and sediment) from the cores can request it.

Once the scientists in this study had the sediment and rocks, they cleaned the rocks of the very fine sediment until they had a good amount of rocks, which were mostly quartz. They then used a certain method to extract and measure the amounts of 10Be and 26Al in the rocks. The idea is that with long-term exposure to sunlight, the rocks would contain high amounts of 10Be and 26Al. This would indicate that at the time the rocks were deposited millions of years ago, the ice on East Antarctica would have to be melted away, and the land surface exposed.

Results: The scientists found little, if any, of 10Be and 26Al in their samples. This indicates that the rocks were not exposed to sunlight, and thus the glacier that covers East Antarctica did not melt back and expose the land surface millions of years ago.

Why is this study important? This study used a novel approach and really cool method to investigate a problem that scientists didn’t agree upon. It also indicates, to some degree, how much the glacier on East Antarctica melted during interglacial (warm periods within an ice age) times over the last millions of years.

Citation:  Shakun, J. D., Corbett, L. B.,  Bierman, P. R., Underwood, K., Rizzo, D. M.,  Zimmerman, S. R., Caffee, M. W., Naish, T., Golledge, N. R., Hay, C. C. 2018. Minimal East Antarctic Ice Sheet retreat onto land  during the past eight million years. Nature. doi:10.1038/s41586-018-0155-6

Grand Canyon Trip

Rose here –

Standing on a rock at Ooh Aah Point, about a mile down the South Kaibab Rim Trail.
A year ago I got the chance to visit the Grand Canyon National Park. I had been there once as a toddler, but of course I didn’t remember it, so I was very excited to have the opportunity to go again now, especially since I’ve been studying geology for a few years. The Grand Canyon is like Disneyland for geologists. There are SO many cool geologic processes and so much geologic time represented there (click here for a fun read on the geology).

Hiking down the South Kaibab Rim Trail and looking back up at the South Rim.
We were staying in Flagstaff, AZ for a conference, but my colleague and I had a free day before it started and since the Grand Canyon is only an hour and a half away we decided to just hop in the car and go. We started off early in the morning so we could try and beat the heat. When we arrived we headed straight to the rim.
It was one of the most exciting moments of my life. I had seen pictures of the canyon, but nothing prepared me for what it was actually like to stand there in person. We walked up to the rim with our eyes on the ground so we would see it all at once. When we got close enough we looked up and were utterly speechless for at least a minute. It was so worth it. The Grand Canyon is so big. Like, SO BIG. Apart from all the cool geology, it is a really amazing view.

Sitting near the edge by the Geology Museum (I was further back than it looks!).
One of the coolest things about the Grand Canyon (besides the size) is how you can really see textbook examples of geologic concepts displayed in a way that anyone can see. For example, the Great Unconformity is a famous example of an unconformity – a place where rocks were deposited or uplifted and then some time passed and/or erosion occurred before more rocks were deposited. The Great Unconformity is the place where the beautiful sedimentary rock layers that make up most of the Grand Canyon are deposited on top of older metamorphic and igneous rocks. The distinct sedimentary rocks layers we see exposed in the canyon help geologists understand what the environment was like at different times in the past. After all these rocks were deposited, the canyon itself was carved out by the Colorado River starting at least 6 million years ago (click here for more information), resulting in the Grand Canyon we see today.

A note from the editor (Jen): I wholeheartedly agree with this description, the view is beyond breathtaking. It takes a while to soak in the awe inspiring beauty. Time is so often taken for granted but when you can see so much time in the rocks, it gives you a new perspective.

A view of the Grand Canyon from near the visitor’s center, looking north from the South Rim.
Me standing at the South Rim, with Bright Angel canyon behind me.