Paleo Podcasts

When I work out, I sometimes listen to a mix of aggressive electronica and high-energy dance music to get me moving. But usually, I use my gym time to catch up on podcasts. My new year’s fitness resolutions mean I’ve been updating my mp3 player with new podcasts, including some paleontology-themed ones. The problem is, when you go to iTunes and search “paleontology”, “palaeontology”, or even “dinosaurs”, you don’t get much. Here are a few for the paleo-minded.

http://www.pasttime.org/

I’ll begin with a plug for my peeps: Past Time is hosted by Stony Brook University grad students Adam Pritchard and Matt Borths. Every couple weeks they post a ~20-25 minute show on some topic relating to vertebrate paleontology, and despite the hominid focus at Stony Brook, it’s rarely about humans. In addition to their entertaining and informative banter (Adam is a perfect straight man to Matt’s charming goofiness), each episode includes an interview with a paleontologist who worked on the topic of discussion. For example, recently they chatted about all these new tyrannosaur species discovered by University of Utah scientists, with Utah professor Dr. Randy Irmis as a guest. The interviews are woven into the discussion on the topic rather than longform interviews. One really awesome feature of Past Time is that they create a “field guide” for each episode, an associated page with tons more information, photos, maps, and further reading, including links to the original scientific papers (here’s the tyrannosaur field guide). The most recent episode is “The Hobbit – An Unexpected Discovery“, which discusses the species of tiny hominids living in Indonesia just 17,000 years ago, Homo floresiensis. This show is definitely kid-friendly (no swearing, shorter), and it’s accessible to non-scientists in language/themes).

For more Past Time, head to their website, subscribe on iTunes, and follow them on Twitter and Facebook.

http://www.palaeocast.com/

You should also check out Palaeocast, a UK show hosted by Dave MarshallLaura Soul, Joe Keating, and Jon Tennant. This show is a bit longer, 30-60 minutes per episode, with a new ep every two weeks. It’s a different style than Past Time; the interviewees are the focus and they have a longer chance to explain their research. Some recent shows I liked are a general overview of marsupial evolution and a discussion of the Riversleigh fauna, both featuring Dr. Robin Beck from the University of New South Wales. Another rad aspect of Palaeocast is that they cover scientific meetings; for example, these recent eps on the Society of Vertebrate Paleontology and the Palaeontological Association annual meetings. The pages for each podcast are image-rich, with pictures from the meetings or from the scientific papers the interviewee discusses. You could play this podcast with your kids in the car (no swearing), but younger kids with short attention spans might not like the longform interviews. Adults, however, will appreciate the clarity and depth of the discussions.

For more Palaeocast, head to their website, subscribe on iTunes, and follow them on Twitter. You can also like them on Facebook.

paleo after dark

Palaeo After Dark features ”informal discussions about evolutionary biology and palaeontology… over beer”, and is hosted by four current or recent University of Kansas geology graduate students: Curtis Congreve, Amanda Falk, James Lamsdell, and Randol Wehrbein. This is also a biweekly podcast, and it’s easily the longest of the bunch (some episodes are close to two hours). This podcast is stylistically a lot different from the ones above; it’s four friends discussing topics relevant to their shared research interests or primary literature. It’s neat to get this perspective into how academics interact with each other; this is far closer to how most science conversations start than the stodgy, formal, or awkward stereotype you see in movies or Big Bang Theory. Palaeo After Dark assumes their listeners are already pretty familiar with paleontological and evolutionary terminology, so it might not be as accessible to nonscientists. It also usually takes a long time to get to the meat of the episode. For example, the gang has over 26 minutes of amusing banter before they begin this interesting discussion of dinosaur ontogeny, taxonomy, and geologic dating. Because this is an informal podcast and alcohol is involved, there is a lot of swearing, so it’s probably not kid-appropriate.

For more Palaeo After Dark, head to the website, subscribe on iTunes, and like them on Facebook.

Dragon Tongues paleontology podcast

Our final paleo-exclusive podcast is Dragon Tongues, a show so new its first episode just aired on January 7th. Hosted by Sean Willett (an undergrad! at University of Calgary who also writes a dino column for UBC Okanagan’s The Phoenix News), Dragon Tongues will air the first Wednesday every month. It’s pretty short if the first episode (15 minutes) is a good indication. The first show begins with a statement of purpose: Sean’s goal is to tell the stories of fossils and Earth history in an accessible format, with each episode focusing on a species, and each season focusing on a theme. Season 1 is about dynasties, and episode one focuses on Carcharodon megalodon. I’m excited about this podcast; Sean has a dynamite radio voice and stylistically it’s sort of a paleontology-version of This American Life. Rather than fanboy gushing over mega-sharks, he tells the story of the role C. megalodon played in understanding what fossils are, and how they shaped our understanding of past life being different. Dragon Tongues is kid-appropriate and non-scientist accessible.

For more Dragon Tongues,  follow it on Twitter and subscribe on iTunes.

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If your main source for podcasts is iTunes, that’s it. Those are the only four paleo-only podcasts they host. However, there are several other science-themed podcasts aimed for a general audience, that feature paleontological topics.

http://tetzoo.com/

Tetrapod Zoology is a relatively new podcast hosted by SciAm blogger Darren Naish and palaeoartist John Conway. As with the blog, its topics include vertebrate paleontology in addition to the biology of living tetrapods, science fiction movies, and cryptozoology. These topics are all mixed into each ~60-90 minute episode, so there are no pure-paleo shows (so far). Recent episodes include discussions of woolly rhinos, mesosaurs (fossil vertebrates somewhat closely related to reptiles), and the tail of Jeholornis (a fossil bird from the Cretaceous of China). The show jumps right into the topic, and usually begins with zoology or paleontology. It shares the tone that makes the original blog work so well; Darren and John are both genuinely interested and it shows. It would be cool if they added links to the papers/books being plugged/discussed to the website, but it’s still new, so maybe this will happen in the future. The shows are kid-friendly and generally accessible to non-scientists (they explain technical stuff), but as I said above, not paleo-exclusive.

Follow TetZoo on their website and subscribe on iTunes. Also, you really should read the blog itself.

radiolab logo

Nothing else sounds like Radiolab. You might have heard it on public radio; it’s nationally syndicated. Each week, a different topic (often scientific, sometimes news or philosophical) is explored, presented from the perspective of the hosts as if they are learning about it in real time. Clips from interviews are woven into the discussion, so listeners follow how the scientists made their discoveries and changed their thought processes. Check out this recent ep in which University of Chicago paleontologists discuss using fossil corals to track changes in the number of days per year through time. Definitely kid- and non-scientist friendly: anyone who is natively curious about the world should like it. It’s one of my favorites, even when the topic isn’t science.

Follow Radiolab on their website, Twitter, Facebook, or iTunes.

science friday

Science fans are probably already familiar with the weekly Science Friday podcast, which is also aired on public radio stations across the US. Each week, host Ira Flatow examines several topics from recently published research, including short interviews with the researchers themselves. Recent episodes include discussions with NSCU grad student Edwin Cadena about car-sized giant turtles from Colombia and a conversation about Utah’s fossil history with Utah professor Dr. Randy Irmis, science writer Brian Switek, and BYU professor Dr. Brooks Britt. And just last week, Dr. Ted Daeschler from the Academy of Natural Sciences, Philadelphia was on the show to chat about the hind limbs of Tiktaalik. Go! Subscribe! Now!

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Given that people find paleontology so fascinating, it’s really weird that there aren’t more dedicated paleo-podcasts. I would have assumed  that there would at least be one weekly or bi-weekly “dinosaur roundup” show…

Do you blast your quads to a different science podcast? Have I missed some in this list? Let me know in the comments section!

Category: Miscellaneous, Paleontology | Tagged , , | 5 Comments

Sharing Phylogenetic Data — Public Comment Invited

Data sharing is important–it helps scientists to reproduce others’ results, add data to previous analyses, and otherwise maximize the impact of an individual publication. This isn’t really news, of course. But, now that we are in a world where data sharing is increasingly the norm, how do we make sharing as easy as possible? It’s not enough to slap some tables up on a personal website or even on an official data repository; the data have to be easily readable by humans and machines, easily reusable, and easily accessible for the long term.

One major goal of biology is to understand the arrangement of the branches on the Tree of Life (phylogenetics). Beyond the general drive to understand what is most closely related to what, a solid tree can help answer all sorts of interesting questions about the patterns and process of evolution. How did gigantism evolve in some dinosaurs? How did bird brains evolve? How did bone-cracking dogs get their beefy skulls? Of course, published trees are “just” hypotheses. The arrangement changes slightly (or occasionally even radically) with the discovery of new species, sequencing of new genomes, development of new tree reconstruction methods, and reinterpretation of old anatomy. Thus, data sharing is crucial for phylogenetics–scientists need to be able to add data, reanalyze old data sets, and reevaluate previous work in order to have the best possible tree.

Evolutionary trees help scientists understand the evolution of bird brains. Image from Smith and Clarke 2012. CC-BY.

Evolutionary trees help scientists understand the evolution of bird brains in concert with the evolution of their lifestyles. Image from Smith and Clarke 2012. CC-BY.

Data tables form the core of phylogenetic analyses, whether the data are in the ACGT of a DNA sequence or the 1′s and 0′s that mark presence or absence for the anatomy of a fossil organism. Alongside the data table are lists of characters, lists of specimens, and all of the other important supporting information. This makes for a complex situation, and there is considerable variability in how different researchers, and even different publishers, present these critical data. Standardization is a must!

Karen Cranston, Luke Harmon and Maureen O’Leary, lead researchers on the NSF-funded “Assembling, Visualizing, and Analyzing the Tree of Life” (AVAToL) project, are drafting a document that lays out best practices for sharing phylogenetic data. This includes trees, aligned gene sequences, data matrices, character lists, and all of the other technical details that underpin an analysis. Maureen relayed to me that she is particularly interested in comments on how to deal with time and other metadata. Are you someone who works with or is interested in phylogenetic data? They’re looking for your input!

The draft “best practices” guidelines are available as a Google Document, freely editable by anyone. In particular, input is requested on guidelines for data storage and formatting. The coordinators for this effort request your comments soonJanuary 22 or 23 at the latest, so act now if you are interested! There are already some great comments on the document.

I applaud the steps that Cranston, Harmon, and O’Leary are taking to make this a true community effort. Too often these kinds of “best practices” documents are crafted in the proverbial “smoke-filled back room,” catering to a handful of insiders. The more open the process, the better the guidelines and the more likely people are to use them! May this serve as a model for future efforts.

Want to add your input? Check out the draft guidelines for more information! 

Category: Miscellaneous, Open Data, Paleontology, Zoology | Tagged , , , , , | 2 Comments

Ichthyosaur is the New Black

Just yesterday, a group of 2nd graders asked me what color dinosaurs were. I was pretty excited to tell them we actually do know this through looking at tiny structure on feathers called melanosomes. Melanosomes are sub-millimeter sized round or cigar shaped organelles inside of animal cells that contain melanin, the substance that causes pigmentation. When we examine melanosomes in modern organisms, their chemical profiles (known as a spectra) tells us what type of melanin is in that melanosome. Eumelanin is responsible for black and brown pigment and pheomelanin is responsible for red or pink coloration. Carotenoids and porphyrins are other non-melanin pigments, and can produce other colors in birds like bright yellow and green. Interestingly, a blue coloration is produced not by pigment but the scattering of light from unique keratin ‘air pockets’ in certain type of bird feathers. This means blue is a structural, not a pigmented color.

Different types of melanin are really the easiest for us to distinguish in fossil specimens due to the fact their chemical profiles are preserved in melanosomes. From this type of research on dinosaurs, we have found out that Microraptor was shiny and black. A feather from the 1861 Archaeopteryx specimen indicates it too was black. This research, up until this point, has mostly focused on examining the melanosomes in birds, but this week, in Nature, this same idea was used to determine the colors of ancient marine reptiles.

This time, Johan Lindgren and coauthors were interested in the colors of extinct marine giants like ichthyosaurs, the mosasaur Tylosaurus, and an extinct leatherback turtle. Scrapings of “skin” were taken from these specimens and put into some special microscopes. The skin of these specimens is a blackish sort of film that, to the naked eye, doesn’t look like anything special. But up close in the scanning electron microscope, it is immediately apparent that the telltale cigar-shaped melanosomes are present. It is important to note fossil bacteria can look very similar to fossilized melanosomes, but distinct chemical signatures only on the body areas of the fossils and not on the sediment outside that zone seem to indicate they were present in life and did not form after death.

The chemical profiles of the melanosomes in all three of these marine reptiles indicated they were black in color because eumelanin was detected. Interestingly, it seems the ichthyosaur was black on the entire body- not just on the dorsal side. The mosasaur and turtle possibly had a dark top and a lighter underside. You may be wondering why any of this matters- what difference does it make if an ichthyosaur was black all over? In the paper, the authors aptly mention coloration is a trait that is subject to natural selection. Coloration in animals influences sexual displays, thermoregulation, and camouflage.  Certain animals can be better adapted to colder environments if their dorsal sides are darker in color, which will allow them to absorb more heat. Cordylid lizards in South Africa that had lower skin reflectance (more melanin) had a higher fitness than species that had lighter, more reflective skin.

Ichthyosaur specimen from the Alf Museum. Courtesy of Andy Farke. CC-BY

Ichthyosaur specimen from the Alf Museum. Courtesy of Andy Farke. CC-BY

Ichthyosaurs may have had eumelanin on their entire body due to a benefit in thermoregulation. If they spent time close to the surface, they could absorb more sunlight and stay warmer in cold environments. Extant leatherback turtles are dark on the top of their shells, possibly for this reason. This pigmentation pattern is called thermal melanism. On the other hand, most turtles and cetaceans are countershaded–dark on top and light on the bottom. This shading in cetaceans seems to obscure their own shadows while they are diving, making it easier to sneak up on prey. Species of whales that possess uniform dark coloration could be better adapted for diving to extreme depths where there is no light, but the evidence for this is mostly anecdotal at this time.

This study indicates for the first time there is convergent evolution of melanism in secondarily aquatic tetrapods, but more importantly expands fossil melanosome analysis beyond just feathers. Not that long ago, determining the color of extinct animals seemed impossible, but now it is very clearly possible for more organisms than we ever imagined!

References: 

Carney, R. et al. 2012. New evidence on the colour and nature of the isolated Archaeopteryx feather. Nature Communications. 3 (637). doi:10.1038/ncomms1642

Clusella-Trullas, S., Hvan Wyk, J., Spotila, J.R. 2009. Thermal benefits of melanism in cordylid lizards: a theoretical and field test. Ecology 90:2297–2312. http://dx.doi.org/10.1890/08-1502.1

Li et al. 2012. Reconstruction of Microraptor and the Evolution of Iridescent Plumage. Science 335 (6073) 1215-1219. DOI: 10.1126/science.1213780

Lindgren, J. et al. 2014. Skin pigmentation provides evidence of convergent melanism in extinct marine reptiles. Nature. doi:10.1038/nature12899

Category: Dinosaurs, Geology, Paleontology | Tagged , , , , | 3 Comments

Q&A with Daniel Field–Weighing Dead Birds

Although we can directly weigh modern birds, we can’t do this with extinct birds–and we need to know body mass to understand their biology! The previous post on this blog reviewed a newly published PLoS ONE paper on how to accurately estimate the mass of a bird from measurements of its skeleton. The senior author on that paper, Daniel Field, was kind enough to answer a few questions about the research and tell us some anecdotes that didn’t make it into the formal publication.

Daniel Field, lead author of the recent study on body mass estimation in birds, with a red-winged blackbird that escaped inclusion in the sample. Photo courtesy Daniel J. Field.

Daniel Field, lead author of the recent study on body mass estimation in birds, with a red-winged blackbird that escaped inclusion in the sample. Photo courtesy Daniel J. Field.

What was the inspiration for your research? 

As you mention in the introduction to your [previous] blog post, body mass correlates with many important biological parameters. Therefore, having an idea of how much a fossil organism weighed can provide important clues about its lifestyle–clues that may otherwise be difficult to infer. Although a considerable body of work presenting methods for estimating the body mass of fossil birds already existed, I was troubled by the fact that most studies investigating fossil body mass only quantify a single, mean mass estimate. This approach is problematic, since a considerable amount of uncertainty exists in our attempts to estimate fossil body mass; only presenting a single, mean estimate oversimplifies the situation, and runs the risk of making estimates seem speciously precise. With our study, we attempted to address this issue by providing simple methods for estimating well-justified 95% prediction intervals for fossil mass estimates.

Was this paper part of a larger project, or an isolated study?

This work constitutes a portion of my PhD dissertation, which will seek to apply well-justified body mass estimates to a variety of interesting problems in bird evolution.

You spent a lot of time in the Yale Peabody Museum collection gathering data for the study…is there any specimen from the project that sticks out in your mind as particularly interesting?

One thing that really emerges when you spend time looking at bird skeletons is the incredible disparity in their hindlimb proportions. Unlike in humans, where the femur and tibia constitute the vertical portion of the leg, the vertical portion of a bird’s leg is composed of the foot (the ‘tarsometatarsus’) and the tibia (‘tibiotarsus’ to be precise). Some of my favourite birds are waders and shorebirds (like herons, flamingoes and sandpipers), which exhibit some of the most extremely elongated hindlimbs in nature. I find the supremely elongated tarsometatarsus of stilts (aptly-named shorebirds of the genus Himantopus) to be some of the most graceful bones in any museum collection. Here’s a link to an image of a flying stilt in Spain, showing off its gangly legs.

Black-necked stilt (Himantopus mexicanus), showing off its amazingly gracile and elongated legs. Image by flickr user winnu - CC-BY 2.0.

A black-necked stilt (Himantopus mexicanus), showing off its amazingly gracile and elongated legs. If you’re not familiar with bird anatomy, you will probably be surprised to learn that the part below the bend in the leg on the animal in this picture (including the tarsometatarsus bone)–is equivalent to most of the sole of our foot. Image by flickr user winnu – CC-BY 2.0.

What was the most challenging part of this project?

With a project of this scale, a challenging issue that emerges is simply one of data management; with approximately 12,000 spreadsheet cells of raw data, simple frame-shift errors can have huge consequences! This was something that we all needed to be mindful of when inputting data, performing analyses, and making corrections.

You used the open source statistical software R for data analysis…how was that experience for you and your co-authors? Did you have much background with the software before this project?

At the outset of the study, only one of our group members (Simon Darroch) had much experience working with R, so his analytical work was crucial. At the time, the prospect of analyzing this much data seemed really daunting to me. However, I had the chance to participate in a statistical workshop geared towards palaeontologists last summer, which gave me my first exposure to R and taught me many skills that will be useful moving forward. Most of the analyses that we present are actually really simple to implement in R, as long as you have a bit of a background.

Thank you, Daniel, for telling us the story behind the paper! If you want to learn more, you can check out his personal website, read my blog post about the body mass estimation paper, or read the paper itself at PLoS ONE.

Citation
Field DJ, Lynner C, Brown C, Darroch SAF (2013) Skeletal correlates for body mass estimation in modern and fossil flying birds. PLoS ONE 8(11): e82000.doi:10.1371/journal.pone.0082000

Category: Interview, Open Access, Paleontology, PLOS ONE, Zoology | Comments Off

How much did that dead bird weigh?

“How heavy was it?” Body mass is not just an intuitive way to compare the size of animals, but it’s also critical for understanding their biology. Numerous scientifically interesting attributes can be related to body mass, such as growth rate, bone strength, and even metabolism. If we want to know if an animal grew unusually quickly or slowly, for instance, we probably want to compare it to animals of the same size. In order to fully understand these sorts of features on broad evolutionary scales, it would be really great to estimate body masses for extinct organisms. But, it’s difficult enough to get a live critter on a scale–so can we even hope to learn something about a dead critter known only from bones?

<i>Ichthyornis</i> died out over 80 million years ago. Can we ever hope to figure out how much it weighed? Image by Nobu Tamura, CC-BY.

Ichthyornis died out over 80 million years ago. Can we ever hope to figure out how much it weighed? Image by Nobu Tamura, CC-BY.

Thankfully, bone size is correlated with body mass. For decades now, scientists have developed methods to estimate mass from simple bone measurements. All it takes is a bunch of bones from animals of known body mass, and then you can write an equation that lets you plug in a bone measurement on one end and get an estimate of body mass out the other end.

The next question is: which bones should you study? An individual skeleton may have dozens or hundreds of bones to choose from, but not every bone will produce a good estimate. Ideally, you want a bone that is weight-bearing. For instance, in humans and other bipedal animals, much of our weight is transmitted through the femur (thigh bone), so you would expect a rather direct relationship between femur dimensions and body mass. Bones that aren’t weight bearing, such as ribs or tail vertebrae, may not produce as accurate of estimates. (Mammalian paleontologists often use teeth because they’re pretty common, but the connection between tooth size and body mass is a complicated one.) Even then, not every part of every limb bone will produce equally accurate body mass estimates, depending on the style of locomotion that an animal uses. Scientists usually use the circumferences of the middles of the shafts on the femur and/or the humerus, the two main weight-bearing bones in most terrestrial vertebrates.

In an ideal world, we would have “One Equation to rule them all” (apologies to Tolkien), but this may not produce the most accurate results. Different groups of animals have different limb bone shapes, and they all hold their limbs slightly differently. An equation that works well for mice may not work well for horses. It makes sense, then, that the best results might be achieved by tailoring equations to specific bones on specific groups of animals.

Want to measure the mass of a dead parrot? You have to weigh a live parrot first! Photo by Tony Hisgett, CC-BY.

Want to estimate the mass of a dead parrot? You have to weigh a live parrot first! Photo by Tony Hisgett, CC-BY.

Daniel Field and his colleagues at Yale University wanted to calculate accurate body mass estimates from the often fragmentary bones of extinct birds. Although previous researchers had taken a stab at this, the samples in many of these studies were sometimes small and almost always only focused on a handful of measurements across the skeleton. Thus, Field and crew were interested in two particular questions: 1) Which bony measurement could best estimate a bird’s body mass? and 2) What was the range of uncertainty on this estimate?

First, the researchers needed to figure out how to accurately estimate body mass in modern birds of known body mass. They measured 863 skeletons representing 317 different species of volant (flight-capable) birds in the collections of the Yale Peabody Museum of Natural History. With 13 measurements on each individual skeleton from the femur (thigh), tibiotarsus (shin), arm (humerus), shoulder (coracoid), and foot (tarsometatarsus) bones, that’s a huge amount of work–over 11,000 individual measurements! Body mass data, which were not always collected for the individual animals that provided the museum skeletons, were taken from the literature.

The researchers calculated statistics that evaluated the relationship between a particular measurement and body mass, and found that one measurement in particular worked better than all of the others. One of the shoulder bones, the coracoid (we humans lost a separate coracoid along the way) has a facet where the arm bone (humerus) attaches. The maximum dimension of this facet predicted body mass better than any other measurement in most of the birds that Field and colleagues looked at (in a few groups, the length of the overall coracoid was a slightly better predictor). Not only did facet length produce an accurate estimate–which many other bones did too–but it produced a tightly constrained estimate. Every time you estimate something from a bone measurement, there is a range of uncertainty. This range was tighter for the coracoid facet measurements than any other measurements. Accurate and precise!

Initially, it is somewhat surprising that part of the shoulder joint would be the best predictor of body mass in birds–after all, when they walk around, they walk around on their hind legs. Field and colleagues speculate that this relationship is due to the needs of flight–you don’t want your shoulder joint to fail when flapping your wings, so it makes sense that large birds would have large shoulder joints, and vice versa.

When it comes to fossil birds, it is very convenient that the coracoid is a good predictor of body mass. Coracoids are one of the more robust bones in the bird skeleton, and the part that contributes to the shoulder joint is one of the more commonly preserved pieces in the fragmentary fossil record of birds. Even when the coracoid is missing, there are now a whole bunch of well-tested equations that can be used on other bones. The work by Field and colleagues means that it will be much, much easier for paleontologists to reliably estimate body mass in a variety of bird fossils.

Skeleton of a parrot, with the coracoid highlighted in blue. Field and colleagues found that the size of the surface where the humerus (arm bone) attaches is the best predictor of body mass in their sample. Image modified from Lydekker, which is now in the public domain.

Skeleton of a parrot, with the coracoid highlighted in blue. Field and colleagues found that the size of the surface where the humerus (arm bone) attaches to the coracoid is the best predictor of body mass in their sample. Image modified from Lydekker 1894/1895, which is now in the public domain.

As an added bonus, the researchers published all of the data they used in their study! This means that anyone will be able to run their own analyses (it would be interesting to see if phylogeny is indeed a minor issue as posited by the authors), add additional specimens, or virtually anything else imaginable.

Coming up next…a Q&A with Daniel Field about the paper!

To learn more, check out Daniel Field’s web page or read the full paper over at PLoS ONE. Nic Campione and colleagues also recently published an open access paper on body mass estimation in terrestrial quadrupeds, which also is worth a read.

Citation
Field DJ, Lynner C, Brown C, Darroch SAF (2013) Skeletal correlates for body mass estimation in modern and fossil flying birds. PLoS ONE 8(11): e82000. doi:10.1371/journal.pone.0082000

Category: Open Data, Paleontology, PLOS ONE, Zoology | Tagged , , , , , | 1 Comment

Developing an Ethic for Digital Fossils

Fossils are part of our planet’s natural heritage. These traces of organisms that lived long before the founding of any nation are essentially the only record of how we came to be. As such, the past few weeks have seen some controversy over the sale and attempted sale of some vertebrate fossils. Many (but not all) paleontologists charge that these sales create a private commodity out of a resource that should belong to all of us.

However, this argument about fossils as our planet’s natural heritage has stuck in my craw. Not because I support unfettered commercialization of fossils (I don’t), but because many paleontologists and many museums send very mixed messages. We say, “Fossils belong to the world!” Then we turn around and say, “But photographs and other digital representations belong to the museum.” As a result, it is nearly impossible for an individual paleontologist to easily and legally distribute digital photographs or 3D scans of fossils without a mountain of restrictions and caveats. In this post, I argue that we need a new and consistent ethic for digital fossils, one that better reflects the idea of fossils as planetary heritage.

Eurychilina reticulata is an ostracod crustacean that lived 455 million years ago. Fossils such as this are critical for unraveling the evolution of earth's biosphere. Scale bar equals 320 µm. Modified from Mohibullah et al. 2012, CC-BY.

Eurychilina reticulata is an ostracod crustacean that lived 455 million years ago. Fossils such as this are critical for unraveling the evolution of earth’s biosphere. Scale bar equals 320 µm. Modified from Mohibullah et al. 2012, CC-BY.

Anyone who has done museum collections work knows about photography agreements. They’re those pieces of paper we never read and sign quickly so we can just get back to looking at fossils. These agreements generally say we’re allowed to take photos and use them for research and personal reference, but agree to not exploit them commercially or do other crass things with them. Examples of photography agreements are actually difficult beasts to find online, but for some examples check out the Harvard Museum of Comparative Zoology policy, or the policy from the Denver Museum of Nature and Science (pdf). Quoting from one, “The MCZ retains the copyright…to the image of any museum owned material.” Wait….what?!!

Usage restrictions for images of museum specimens are not unusual, and in some cases even somewhat understandable, but what do these restrictions say about the museum specimens? It’s pretty simple–these restrictions imply that museum specimens are not the world’s heritage, but the property of an institution. On the one hand, considering fossils as “museum property” makes sense from an insurance perspective and in emphasizing that a museum is responsible for specimen care. However, I argue this is not consistent with an ethic of fossils as global heritage.

If fossils are indeed part of our planet’s natural heritage, we need to start treating them this way. Not just by preserving fossils from mishandling, theft, and breakage, or by protecting field localities from unauthorized collecting, but by opening up digital access to every single person on the planet. We can’t have it both ways, by claiming fossils as planetary heritage on one hand and unduly regulating images of this heritage on the other.

I envision a world in which researchers and the public alike are allowed and even encouraged to post digital representations of fossil specimens, with minimal restrictions. This is not to say that all of those who create photographs or digital replicas of specimens should be forced to share them (except for cases where data sharing is necessary). Unless otherwise requested as a condition of specimen access or unless the data go into a publication, the person who gathers the data should be free to do with them as he or she pleases. It is just unethical for research museums to prevent those who want to distribute representations of fossil specimens to do so. I have a massive personal database of specimen photographs and CT scans–but as near as I can tell, I am virtually prohibited from posting many of them freely (e.g., high resolution, CC-BY license or public domain dedication) without extensive negotations (if I’m lucky), because there is a chance that someone else might use them for “unauthorized purposes”.

I have discussed this issue a few times with many colleagues, and inevitably they raise a few standard objections.

“If digital copies are available, why would people want to come to the museum to see the original?” Ask the Louvre. Ask the American Museum of Natural History. I could have a whole house full of copies of museum specimens, but at the end of the day this just makes me that much more interested in seeing the originals. The originals are interesting because they are the originals! This is what drives the commercial fossil trade, and this is what keeps visitors streaming through the doors of museums. (thanks to Heinrich Mallison for articulating this response to me so well in a conversation at the most recent SVP meeting)

“If anyone can do anything with images and scans of fossils, won’t museums lose out on revenue? This revenue helps museums pay for preservation of their collections!” This argument is seductive and not without its merits. Museums do need money, after all! However, it is flawed in two aspects. First and foremost, the vast majority of images and digital scans of the vast majority of fossils at the vast majority of museums have little if any potential for revenue generation (unless there is a sudden demand for high resolution photographs of partial horse teeth in orthogonal occlusal and lateral views). These 99.99% of specimens are effectively being held hostage in hopes that the remaining 0.01% will generate some money for the museum. Second, there is nothing saying that museums cannot generate money from casts or their own artistic photographic databases. A museum is not obligated to release its own photos or allow anyone to use its own molds, but neither should it restrict distribution of the products of (non-damaging) photography and digitization by others. Similarly, museums should have the right to be compensated reasonably for facility use. It costs money to keep the lights on and takes valuable staff hours to shepherd photographers. But once the photos or scans are taken of objects that belong to the world, how can a museum ethically dictate use of these images?

The nightmare scenario of someone profiting off of images of fossils.

The nightmare scenario of someone profiting off of images of fossils.

“But won’t someone make a [creationist textbook / pornographic film / action figure] of our fossils that will make the museum and the science look bad?” As already noted, the great majority of fossils (and images of fossils) are virtually useless from the perspective of commercial reproduction. There is thus little reason to clamp down on everything in the pursuit of control over a handful of potentially annoying cases.

Furthermore, you can already find images of specimens or casts of specimens from many major museums in just about any unsavory context. This includes specimens originally from the collections of the American Museum of Natural History on the cover of creationist treatises or casts of fossils originally from other major museums photographed in situations of exceptionally poor taste (I am not linking to those here, for reasons that are hopefully obvious). I severely doubt that the museums have the time or need to clamp down on such uses of images of “their” fossils.

One potential problem, of course, is that image credits may be seen by some as endorsements. For instance, the license associated with a CC-BY figure from a PLoS ONE paper means that anyone can reuse it provided the original authors are credited. So, this means that a figure from Farke & Sertich 2013 could appear in a creationist textbook alongside text that claims falsehoods about the age of fossils, along with an image credit to “Andrew A. Farke and Joseph J. W. Sertich”. Although I obviously wouldn’t like this use of the image, I also think you’d have to be a real idiot to think that reproduction with credit for the source implies endorsement. Not to mention the fact that someone who wants to dig deeper will end up at the original research paper with its valid information. Is it any different from a right-wing or left-wing website quoting Shakespeare with attribution? And, do we really want to go down the road of deciding who should and shouldn’t be allowed to use fossils that are part of the world’s heritage? Such logic bites both ways. Is this really much different from denying specimen access to a research rival?

“If you just ask the museums, they’ll let you post the images under your desired license.” This may be the case for some museums, but it represents both an unwieldy step (particularly for large data sets) as well as an opportunity for unnecessary red tape and stalling by institutions. I would far prefer to see permission to do such things granted at the time of photography or scanning. Some might also argue that these rights are already granted when museums allow photography for research–however, I am not so sure on this from the agreements I have read.

“Museums need to be able to track usage of their specimens.” This is an excuse for limiting digital distribution of fossil data, but it is not a reason. Thanks to the magic of metadata and search engines, it is actually possible to find out who is mentioning certain specimens (for instance, there are 281 mentions of AMNH 5244, a Montanaceratops braincase, according to a Google search, and around 40 mentions in the scientific literature according to Google Scholar). A search for “Tyrannosaurus” brings up images that can be fairly easily matched to relevant museums. It isn’t difficult, and it especially isn’t difficult today.

Just one example of the seedy underbelly of the Internet that awaits us if we disseminate fossil images willy-nilly.

Just one example of the seedy underbelly of the Internet that awaits us if we disseminate fossil scans willy-nilly. Hadrosaur radius (left) from Godefroit et al. 2012; sirenian petrosal (right) from Benoit et al. 2013; all CC-BY. For those who might be concerned, this is a parody.

First, Do No Harm
A museum’s responsibility with a fossil collection is to preserve the specimens for research, education, and exhibit. This is exactly why most fossils are kept behind locked doors under climate-controlled conditions, why sensitive locality data are not disseminated, and why trained museum personnel are the ones who (should generally) make decisions about procedures that may affect fossils. Museums may reasonably restrict photography and scanning if an unpublished specimen is under active study, or they may restrict handling and transport if these activities unduly risk damage to the fossil. However, once the photography or other imaging is cleared from the perspective of specimen safety, there is little reason not to allow unfettered use of the imagery. This does not harm the physical specimen, and arguably it reduces the need for handling of the specimen while increasing usage of the specimen–a long-term good. And as mentioned above, if fossils belong to the world, why should museums restrict distribution of various representations of fossils?

The Barn Door is Already Open
Another reality is that “unauthorized” use of images of specimens from museum collections is already rampant. A quick search on CafePress turns up all sorts of fossils on t-shirts and mouse pads that are almost certainly not expressly permitted by the museums. Thingiverse has (almost certainly unauthorized) printable 3D models of fossils on exhibit at major museums. Wikipedia articles are populated by photos of exhibit specimens, many taken without “proper” authorization or distributed under inappropriate licenses according to a strict reading of many museum public photography policies.

These uses may technically be unauthorized in many cases, but in nearly every single instance they are beneficial to museums and beneficial to paleontology as a field. Digital reproductions allow the public to engage with fossils in a way they might not get to otherwise. Digital photos allow the public and researchers alike to access fossils they might not have physical access to. Photos and CT scans reduce handling of delicate specimens, facilitating specimen conservation. Slapping unnecessary copyrights and restrictions on distribution of images does not help. At best, this provides an artifical sense of security, and at worst it discourages researchers from sharing their data. It certainly has discouraged me from sharing mine.

And let’s not forget…when scientists sign over copyright for their research papers to publishers, the museums that house the specimens will never see a single penny. An image in Cretaceous Research will return profits to the shareholders of Elsevier, but none of these profits revert to the institution (or the researcher). The revenue from an article describing a new species and published in Journal of Vertebrate Paleontology will support the activities of the Society of Vertebrate Paleontology (a worthy cause), but nothing will be returned to the museum for the care of that specimen. A paper with a figure of a dinosaur skull on the PLoS ONE website generates ad revenue for long-term maintenance of the journal, but nothing to pay for conservation materials to stabilize the fossil. Somewhat ridiculously, most museums (and paleontologists) have no problem with this but would be annoyed if I created a personal website that distributed my personal photos of these same specimens under a public domain dedication.

During a time when museums and science are under fire from nearly every financial and political quarter, do we really need another way to reduce access to museum specimens and fuel critics who deride “elitism” in our scientific, educational, and cultural institutions? If public museums want to distinguish themselves from the dreaded privately owned collection in someone’s summer cottage, make the imagery and scans of public fossils as public as possible! Cut out the caveats and restrictions that imply fossils are private property.

In the end, I understand why museums and paleontologists want some control over images and 3D scans of fossils. It’s a scary world out there. We need and have to abide by the regulations in place right now. But, fossils belong to the world. We can’t have it both ways. Let the world distribute and access fossil imagery.

Summary

  • If paleontologists and museums claim that fossils are part of the world’s heritage, unnecessarily restricting distribution of and access to digital representations of these specimens conflicts with an ethic of fossils as world heritage.
  • Museums and paleontologists need to develop an ethic for reproduction and distribution of fossil specimen imagery that ensures access to the greatest number of people with the fewest restrictions.
  • Even if researchers and members of the public with digital images and scans shouldn’t be required to share their data, they should be allowed to do so under a license of their choosing.

Closing Note: This is probably a provocative article for many, but I think the field of paleontology needs to wrestle more deeply with what it means for fossils to be “natural heritage” in the “public trust” (to borrow terms from the Society of Vertebrate Paleontology’s ethics statement). Have we gotten so wrapped up in the idea of copyright and museum property that we have lost sight of what it means for something to be a scientific and global resource? Is there still a place for museums to claim copyright on fossils where legally allowed? I’ve certainly been doing a lot of thinking about it lately, and encourage a discussion in the comments section. Opinions presented here are my own and are evolving. 

Category: Digitization, Open Access, Open Data, Paleontology | 18 Comments

One Year of Integrative Paleontology!

It has been one year since our inaugural post, and time has indeed flown by. In honor of this milestone, each blogger highlighted a favorite post from the last 12 months.

The Jurassic moth Mesokristensenia sinica

The Jurassic moth Mesokristensenia sinica, modified from Zhang et al. 2013. CC-BY.

Blogger Favorites
Sarah Werning picked her post on “Why Paleontology is Relevant” as a personal favorite. Although paleontologists are great at talking about why we are important, Sarah posited that at least some of the oft-cited reasons (e.g., we’re great at teaching anatomy) don’t cut the mustard. Instead, we need paleontology to understand our world today and the changes that it is undergoing. A vigorous discussion resulted.

Andy Farke cheated a bit, and picked a series of posts on proposed United States Forest Service regulations for paleontology on Forest Service lands. The series stimulated lots of productive discussion, largely thanks to the good faith participation of many people from all backgrounds–government paleontologists, museum paleontologists, private citizens, and the like.

Shaena Montanari selected her post on “Paleoecology and Poop” as a highlight for the past year, in which she highlighted the surprising amount of recent research on prehistoric droppings. It’s a poop renaissance, if you will!

So, check out these posts–and don’t forget to check out some exciting new posts that are on the way from our bloggers in the next few weeks!

Category: Background, Miscellaneous, Navel Gazing, Paleontology | Comments Off

The Colorado Plateau Coring Project: Getting Dates in the Triassic

Yesterday I wrote about how rocks layers are aged. After rock layers are lined up and put in relative order, they are dated radiometrically to get their age in years. Terrestrial rocks are difficult to date using relative ages alone, because the divisions of geologic time are defined based on changes in marine fossils (like ammonites and conodonts), which are rare in terrestrial rocks. We can make rough correlations if terrestrial layers are bracketed above and below by marine layers, which happens when sea level rises and oceans spill onto the edges continents. But the oceans reach continental centers  rarely, so long stretches of time may occur between the marine “brackets” that allow terrestrial correlations.

A lot of neat stuff has happened on land during the history of life, from the birth of flowering plants to the origins of humankind. If we had a better grasp on the exact dates that these important events happened, then we could place them in context of things happening elsewhere on the planet: volcanic eruptions, asteroid impacts, climate change, etc.

One time of particular interest is the Triassic Period. Not only is it bounded by two enormous mass extinctions, but the Triassic is when all the major groups of land vertebrates alive today got their start: the ancestors of crocodiles and birds, frogs and salamanders, mammals and lizards all first appear or begin to diversify in the Triassic. What caused this burst of diversity – recovery from the biggest mass extinction of all time, climate change, rifting continents, or something else?  How long did it take – was it simultaneous around the world or region; did it have pulses? The answers are in the rocks, but unfortunately, Triassic terrestrial rock layers are poorly correlated and poorly dated compared to other parts of the global geologic column.

Colorado Plateau Coring Project

Logo by Steven Seppi. Used with permission from the Colorado Plateau Coring Project.

Enter the Colorado Plateau Coring Project. The Colorado Plateau is an area covering about 130,000 square miles of Utah, Colorado, Arizona, and New Mexico. It’s well known for its dramatic geology and incredible national parks, including the Grand Canyon, Arches, Canyonlands, and Petrified Forest. It’s also rich in Triassic rocks and fossils. If the Colorado Plateau was better aligned to the global rock record and better dated radiometrically, it would be key to answering those questions above. The Colorado Plateau Coring Project (CPCP) is funded by the International Continental Drilling Program (ICDP)-funded and National Science Foundation to do just that.

Petrified Forest National Park preserves an especially rich record of the terrestrial Triassic, and comprises nearly 100 million years of continuous rock layers, many rich in fossils. So it makes sense that the CPCP would begin their alignment and dating efforts here. This is a large, collaborative project involving scientists at several universities: Randall Irmis (University of Utah; Natural History Museum of Utah), George Gehrels (University of Arizona), Paul Olsen (Lamont-Dougherty Earth Observatory, Columbia University), Dennis Kent (Rutgers University), John Geissman (University of Texas at Dallas), and Roland Mundil (Berkeley Geochronology Laboratory). For the past two weeks, the team has been at Chinde Point in Petrified Forest drilling a core half a kilometer deep to get the basic rock data to align and date the Colorado Plateau.

Last week, I interviewed Randall about the details of this important research project.

Chinde Point, petrified forest

Chinde Point at Petrified Forest National Park preserves a nearly continuous sequence of Triassic rocks spanning ~100 million years. Image courtesy of the Colorado Plateau Coring Project.

SW: What are the main goals of the CPCP?

RI: The CPCP aims to recover a nearly-continuous record of sedimentary rocks from the Early Mesozoic (252-150 million years ago) of the Colorado Plateau. This record will be recovered using continuous rock cores recovered from at least five different locations around the plateau. Our first stage is to core the entire sequence of Triassic sedimentary rocks at Petrified Forest National Park; these are the Chinle and Moenkopi formations.

SW: What are you hoping to learn? Will the CPCP tell us anything about the biology of extinct animals or climate change?

RI: We hope to answer the following major questions:

  • What is the tempo of climatic and biotic change during the Triassic, such as the rise of dinosaurs?
  • How did changes in greenhouse gases (e.g., CO2) affect ecosystems and the environment during the Triassic Period?
  • What caused a sudden change in plant and animal species at about 215 million years ago – could it have been a meteorite impact that hit Quebec at about the same time?
  • How do Triassic ecosystems and environments in western North America compare with those from the same time in eastern North America, Europe, South America, and Africa?

SW: What is a core – is it a common way to study rocks? Do you find fossils in the cores?

RI: Cores are basically columnar cylinders of rock drilled from a borehole using a diamond-studded bit, which is hollow in the middle.  Cores are a common way to study subsurface rocks in the petroleum and economic geology industry.  They’re also the primary way we study deep sea sediments.  However, the application of scientific drilling (i.e., not for industry) to continents has been a fairly recent phenomenon.  Fossils can be found in the core, particularly invertebrates and microfossils, but the primary goal of the core is not to recover vertebrate fossils.

sediment cores

Triassic sediment cores from Chinde Point. Image courtesy of the Colorado Plateau Coring Project.

SW: What do you do with this column of rock once you have it?

RI: We can do almost everything with the core that one would do with traditional rock samples from surficial outcrops.  The first step is to characterize the stratigraphy and sedimentology – to understand where in section we are and what depositional environments are represented.  The core is precisely oriented relative to both north and vertical, which allows us to look at paleomagnetism to develop a magnetic polarity stratigraphy.  We will take samples for radioisotopic dating, organic and inorganic geochemistry, etc.

SW: Where will most of the research take place?

RI: Once we finish drilling, the cores will go to University of Texas-Austin to be CT scanned.  They will then travel to LacCore at University of Minnesota where the cores will be split in half lengthwise, imaged, and analyzed for natural gamma radiation and other variables.  One half will be permanently archived at LacCore, and the other half will go to Rutgers University where the science party will meet to describe the core and sample it.  Most of the actual research will happen at a host of different institutions, including but not limited to Columbia University, Rutgers University, University of Texas-Dallas, University of Arizona, Berkeley Geochronology Center, University of Utah, and University of Oslo.  In addition to the PIs (Paul Olsen, Dennis Kent, John Geissman, George Gehrels, Roland Mundil, and myself), a number of graduate students and postdocs are involved in the project, and I’m sure undergraduates will be involved as well.

CPCP fieldwork is an all day, every day operation that lasts several weeks. Image courtesy of the Colorado Plateau Coring Project.

CPCP fieldwork is an all day, every day operation that lasts several weeks. Image courtesy of the Colorado Plateau Coring Project.

SW: How does coring differ from traditional paleontology fieldwork?

RI: The timeframe of drilling varies greatly, depending on the characteristics of the rock and how long of a core you want to drill (or how many cores).  This core will be somewhere between 450-500 meters long, and we expect it to take a couple of weeks to drill.  One big difference from traditional fieldwork is that drilling occurs 24 hours a day, 7 days a week.  The equipment is so expensive that it’s best to maximize time on the site.  We work in two twelve hour shifts – in this case one from 8am to 8pm, and another from 8pm to 8am.  The crew consists of two to three drilling staff from the contracted drilling firm, and 3-5 folks on the science team who log and process the core as it comes out of the ground.

SW: Why can’t you get these data from looking at rocks on the surface?

RI: The two main keys to the core are that it gives you unambiguous stratigraphic superposition, and completely unweathered fresh rock. What the first point means is that you know that you have a single column of rock and don’t have to worry about inferences from horizontal stratigraphic correlation. In most cases the advantage of the core over sampling surficial outcrop is data quality and resolution.  For detailed sedimentologic/stratigraphic, paleomagnetic, and geochemical sampling, one would have to dig trenches at least 1-2 meters deep to reach fresh unweathered rock. The time it takes to do this limits the density of sampling to a couple of samples per meter at best, and would take many months to complete over the ~450 meters of section we are coring.  One other main benefit of our core is an innovation of my co-PI Dennis Kent – drilling the core at a 30° angle from vertical.  This means we can very precisely orient the samples for paleomagnetic work, and it gives us more rock per stratigraphic layer, which is useful when you’re taking so many samples from a 2.5 inch diameter core.

The outside of a hill is weathered and potentially chemically altered. Cores sample unaltered rock from the inside of the hill. They can also sample below ground.

Rocks on the surface are weathered and chemically altered from exposure to the environment. Cores sample unaltered, unweathered rock in a single column, and can sample far below ground, which is hard to reach with shovels and picks. Sampling at an angle results in more rock to analyze (the diagonal is longer than the vertical).

SW: Why hasn’t coring been attempted before?

RI: The proximate reason is cost – this core costs just under US $1 million, and that doesn’t include any of the science we’ll be doing.  That being said, scientific continental drilling is quickly becoming more common in deep time rocks (i.e., before the Pleistocene), particularly as specific funding sources for these types of projects are becoming available.  A broader answer is that as scientists refine their scientific questions, we need better age control and data resolution, so we haven’t necessarily needed the resolution provided by coring until recently.

SW: Why did you start with Petrified Forest?

RI: We wanted to start with a core that was both logistically manageable and maximized integration of existing data. Petrified Forest National Park has been a great partner in the project, and has been very supportive the entire way.  They’ve provided housing for the science team, and encouraged visitors to stop by to learn about CPCP.  We’re drilling in the gravel parking lot at Chinde Point, so its easy to get equipment/personnel in and out, and that way we’re also not adversely affecting any park resources.  The Triassic rocks at Petrified Forest NP and surrounding areas have been well-studied for quite a while, so there’s a very large dataset of environmental and paleontologic information that we can immediately integrate with the core to get a holistic picture of the story during the Middle and Late Triassic.

SW:  How many of these cores do you have scheduled and where else are you going to drill?

RI: Currently we are focusing on the first core at Petrified Forest National Park, which will cover nearly all of the Upper Triassic Chinle Formation and all of the Lower-Middle Triassic Moenkopi Formation.  Some late-breaking news is that we’ve just received additional supplemental funding from the International Continental Drilling Program (ICDP) to drill a second shorter core in the Chinle Fm in the southern part of the park. This will allow us to precisely test using geochronology the stratigraphic correlations that have been proposed between the northern and southern part of the park, and therefore also test the biostratigraphic schemes built on these correlations (e.g., Parker & Martz 2011).  This is particularly relevant for understanding the biotic turnover at ~215 Ma that might correlate with the Manicouagan impact event in Quebec. In the longer term, we have plans to core a total of five sites across the Colorado Plateau, which span rocks that range in age from 250 million years old to 145 million years old.  Coring of these future sites will require additional separate funding.

The Manicouagan crater in northern Quebec is an  impact crater so large it can be observed from space. The impact occurred at the end of the Triassic. Image in the public doman, originally from NASA and accessed on Wikipedia.

The Manicouagan crater in northern Quebec is an impact crater so large (70 km diameter) that it can be seen from space. The impact occurred at the end of the Triassic (~212 million years ago). Image in the public domain, originally from NASA and accessed on Wikipedia.

SW: Who is funding the CPCP, and how long did it take to get the money together for such a big endeavor?

RI: The Petrified Forest core is graciously funded by the National Science Foundation and International Continental Drilling Program.  Just the costs associated with the drilling alone are almost US $1 million.  The project was initiated with workshops in 2007 and 2009, and we submitted our first proposals for funding in late 2009.

SW: Are there economic benefits or museum exhibits planned? Will the research benefit people outside the sciences? 

RI: There are definitely plans for a strong component of outreach and communication about the results of the project, through exhibits and public programs at Petrified Forest National Park as well as at each PI’s individual institution.  In fact, the drilling site itself can be visited by anyone who is visiting the park – so we’re an active ‘living exhibit’ at the moment.  The research that will come out of the core has direct societal benefits in that it will elucidate how ecosystems change in a warming world with high CO2, something we all face with anthropogenic climate change over the next century.  The project directly or indirectly supports dozens of jobs in the drilling industry, both through the drilling contractor itself as well as a wide variety of sub-contractors for everything from drilling mud to water supply to rental of generators and work lights.

SW: Thanks so much for all your time, Randy! How can we keep track of CPCP progress between now and publication?  

RI: The best way to follow the CPCP is via our Facebook page and blog.  I should give a shout out to Steven Seppi for designing the beautiful project logo.

——-
Literature cited: Parker WG  and JW Martz. 2011. The Late Triassic (Norian) Adamanian-Revueltian tetrapod faunal transition in the Chinle Formation of Petrified Forest National Park, Arizona. Earth and Environmental Science Transactions of the Royal Society of Edinburgh 101: 231-260.

Category: Climate Change, Geology, Paleontology | Tagged , , , , | Comments Off

Geologic time vs. absolute time

Tomorrow I’ll post an interview with Dr. Randall Irmis, a geologist and paleobiologist working on the Colorado Plateau Coring Project. Today, I offer some background information on the geologic time scale and why it is so hard to figure out how old rocks are.

Earth’s history is divided into different chunks of geologic time, going all the way back to the formation of our planet. Unlike calendars or clocks, which divide time into units of equal length (e.g., days or seconds), the divisions of geologic time aren’t the same length.  For example, the Mesozoic Era was ~186 million years long, whereas the preceding Paleozoic Era lasted ~289 million years. At 2.6 million years, the Pleistocene Epoch was much shorter than the Miocene Epoch (20.4 million years long).  These divisions may seem arbitrary at first, but they’re not; geologic time is based on the succession of rock layers. Geologic time was the first method scientists used to understand the sequence of events in Earth’s history. More recently, we’ve used other methods to associate actual dates with different rock layers, thus linking geologic time (a relative method) with absolute time (= numbers of years old). This merger of geologic time and absolute time is the geologic time scale. (Don’t have a geologic time scale handy? Get one here for free!)

Geologic time is hard to sort out. The first step requires understanding the relative order of the rock layers. For almost 1000 years, we’ve recognized that rock layers are organized in the order in which they were deposited. This idea was first put forth by the Persian polymath Avicenna, and later presented more formally by the geologist and Catholic bishop Nicholas Steno. They proposed that within a vertical column of rock layers, the oldest ones are on the bottom, and the youngest are on top. Today, we call this the principle of superposition. Related to superposition is the principle of original horizontality, which just means that rock layers are more or less horizontal when they are first deposited. Horizontality is important because today’s rocks are not always in their original orientation.

According to the principle of superposition, each rock layer is younger than the one it sits on, and older than the one it lies beneath. In this image, layer I is the oldest layer, and layer A is the youngest.   Image © 2013 Sarah Werning.

Superposition: each rock layer is younger than the one it sits on, and older than the one it lies beneath. In this image, layer I is the oldest layer, and layer A is the youngest.

Of course, the real world is more complicated than the above image. After rock layers form, their position can change through faulting or deformation. For example, the entire column can become tilted, in which case the rock layers get older or younger as you move horizontally along the ground, rather than vertically up a cliff:

syncline! look it up!

Tilted rock layers in the Rainbow Basin Natural Area near Barstow, CA. The rocks were originally deposited as a stack of horizontal layers but were later tilted through geologic processes. As you move from left to right in this picture, the rock layers go from oldest to youngest. Image © 2008 Sarah Werning.

There’s no place on Earth where rock layers going back to the beginning of the planet are visible all in one place, for several reasons. First, some of the layers are underground, so even if they’re present, we can’t always see them. Second, conditions aren’t always ideal for new rock formation, so there are times/places where new rock layers aren’t deposited. Also, rock layers erode at different rates in different places. For example, if there is a river running between two hills, the old rock layers will erode faster there than at the top of the hills. New rock layers are more likely to form in the riverbed and adjacent floodplains than on the hilltops. Different rates of erosion, deposition, and tectonic activity mean that the relative order of rock layers can be difficult to sort out in some places. To illustrate, look at the first image of rock layers above, with layers A through I. Let’s pretend that after layer A was deposited, a river carved out a valley:

CPCP layers erodedDepending on which  mountain you’re on, you might not see layers B or C. Also, there is no trace of layer A in this whole region, although it may be preserved somewhere else. Now, let’s say that after some more time, sediments accumulate in the valley and new rock layers begin to form:CPCP layers eroded new These processes occur over thousands or millions of years, so we can’t observe them in real time. But we can reconstruct the relative sequence of some events. For example, Layer 1 is older than layers 2, 3, and 4, which lie on top of it (thanks, superposition!). Layer 1 is younger than layer E (and F, G, H, and I), because it sits on top of E. Based on how layers 1-4 fill in the valley, we can also conclude that the erosion creating the valley likely happened after layer C was deposited. However,  in order to figure out if layer 1 is younger than layer B, we would need to look at another mountain that preserved both B and 1 in the same vertical column.

Once you have the correct order of your rock layers sorted out, you can begin to associate the rock columns in your area with columns in other regions. If at least one rock layer stretches for miles and miles, it’s easy to confirm you’re dealing with the same layer. In the image below, you can just walk along the grey layer from point 1 to 2 to establish that it’s the same layer in both places. You might then hypothesize that the red layers are the same layer, based on their position relative to the grey layer.

CPCP walk outcrop

More often than not, aligning rock columns is more complicated than this. Parts of your column might be underground, you might be missing rock layers from erosion, and/or the layers might vary regionally in thickness. Also, not all rocks deposited at the same point in time are identical. The appearance of rock layers depends on the local chemical and environmental conditions when they formed. Layers forming under the deep ocean will look very different than those forming in a coral reef, riverbed, desert, or swamp. Even more confusing, if environmental conditions are very similar, rocks deposited at two different points in time might look similar. So what’s a geologist to do?

One line of evidence for simultaneous deposition is when two layers contain the same fossil species. This is much easier to do for oceanic rock layers, because some ocean species (e.g., foraminifera, conodonts) are found around the globe. The types and sequence of these fossils can be helpful in lining up distant rock columns.

layers with seaLet’s say columns 1, 2, and 3 are rock columns separated by thousands of miles. In this picture, fossils are white, blue layers were deposited underwater, and the other colors formed in terrestrial environments. Columns 1 and 3 are mostly terrestrial, but there are three times when the ocean invaded the land – times of high sea level or inland seas. Because the oceanic fossil species are identical, these are probably the same layers seen in column 2; if so, these layers represent the same points in time in all three columns. The sequence of the oceanic fossil species is important, too: triangles, then hearts, then circles in all three columns. It’s more evidence that we are dealing with the same overall sequence of events. If these are the same oceanic layers  in columns 1 and 3, that means that the terrestrial layers between them are roughly correlated in time (I say “roughly” because there might be erosion or deposition gaps in one or both of the columns). Using the sequence of fossil species to correlate rock layers across big distances is called biostratigraphy, and it was extremely important for understanding the basic succession of rock layers on a global scale. Biostratigraphy is still important today for oil exploration, and is also used to align bores when drilling tunnels.

Once scientists had the rock layers aligned and their basic relative sequence sorted out, they noticed large-scale patterns in the succession of the fossils at a global scale. For example,  individual species of ammonites were good for correlating very small chunks of the rock record. At the same relative point in the rock column, all ammonite species disappeared in rock formations all around the world. Globally, blastoids, trilobites, and acanthodians were common in oceanic rocks up until a certain point, after which those types of fossils were never found again. Above that point, totally different types of fossils were found, such as plesiosaurs. Similar patterns were found in oceanic fossils as in terrestrial animal and plant fossils. Because these major shifts in fossil faunas and floras occurred simultaneously all around the world, biostratigraphers recognized that they could be used to bracket and define major regions of the rock column. Smaller shifts (between species rather than faunas) could be used to bracket smaller subregions of the rock column.

This is still how geologic time divisions are defined; saying “Triassic Period” is just shorthand for “the time represented by the chunk of the global geologic column between when we first see the conodont species Hindeodus parvus, up until we start to see the ammonite Psiloceras spelae tirolicum and the foraminiferan Praegubkinella turgescens” (seriously).

Metapolygnathus praecommunisti

Triassic conodonts. Image modified from Mazza et al. (2011), figure 2.

You might be asking yourself, “Well, if the fossils define the geologic time periods, isn’t it circular to use geologic time to tell us how long ago those fossils lived?”

Good question, but no. Remember that geologic time only tells you relatively how old something is; it doesn’t give us an age in terms of number of years ago. Let’s use this analogy: my High School Era is defined as “the time between when I first started attending high school up until I graduated high school”.  In the stratigraphic column of my life, the High School Era came after the Junior High Era, before the Undergraduate Era, and partially overlapped with the I Worked At A Movie Theater Epoch. If I find an essay I wrote for Mrs. Strutzel’s AP English class, I can tell you that it was written sometime during High School Era, and therefore before Undergraduate Era. But that doesn’t tell you how old I was in high school, or how many years ago that happened.

Can you believe those early-2000s fashions? Good Lord!

Sometime during the I Worked At A Movie Theater Epoch.

To find out how old something is in terms of years, you need a different metric, one that can determine absolute time. One common way to do this is radiometric dating. Radioactive isotopes are unstable. They break down (decay) over time, until they become stable isotopes (ones that don’t decay). Each radioactive isotope decays at a specific rate and results in specific stable isotopes – these are just basic properties of the atoms themselves. To estimate when that process started, you first take a substance and figure out its ratio between the radioactive isotopes and the stable (post-decay) isotopes. Then, you can use the rate of isotopic decay (also known as the half-life) to determine how many years of decay it took to result in that ratio – in other words, how many years since the process began, when the substance was 100% radioactive isotope and 0% stable isotope.

Carbon-14 is a radioactive isotope you’ve probably heard of. We use carbon dating to determine the ages of once-living things because it is present in plant and animal tissues. Carbon-14 decays pretty fast; a rate of 50% decay every 5,730 years. That rate of decay means Carbon-14 will completely convert to the stable isotopes Carbon-12 and Carbon-13 within ~60,000 years. This is a long time compared to the High School Era, but really short compared to the age of most rocks. So, we use other isotopes to date rocks; ones that decay at a slower rate. Common methods for dating rocks include uranium-lead dating and potassium-argon dating. These isotopes have much slower rates of decay (i.e., longer half-lives): the radioactive Uranium-235 converts to Lead-207 at a rate of 50% every 704 million years, and Potassium-40 converts to Argon-40 at a rate of 50% every 1.3 billion years.

Using radiometric dating methods, we can link absolute time to geologic time. These methods have already been used to date the rock layers containing the oceanic fossils that define and bracket the divisions of geologic time. So we now know how long each major division of geologic time lasted. Radiometric methods also have been used to date some terrestrial rock layers. Rather than roughly correlating terrestrial layers based on their associations with oceanic rock layers, we can now compare dates of terrestrial layers directly. As more and more rock layers are tagged with absolute dates, the geologic time scale is getting finer and finer resolution. As a result, we have a much better understanding the timing of events in Earth’s history and in Life’s history.

Tomorrow, I’ll talk more about a major new NSF-funded project that is extremely important both for aligning rock columns (calibrating geologic time) and putting absolute dates on individual rock layers (calibrating absolute time) from the Triassic Period.

Category: Background, Geology, Paleontology | Tagged , , , , | 8 Comments

Prehistoric Platypus: Revenge of the Monotremes

(I tried to make the title of the post sound like a SyFy movie title, let me know how I did)

 Obdurodon tharalkooschild is not your garden-variety platypus.

Today, the platypus is one of two remaining varieties of living monotreme (the other being echidnas). I could go on and on about the platypus- it does too many cool things to mention them all.  Ok, ok, I will name one. The male platypus both has pointy ankle spurs that contain venom (females have the spur, but no venom).  This venom isn’t fatal to humans, but is, of course, extremely painful. How is this known? Well apparently a guy wanted to test it out by getting stabbed in the hand by a platypus in the early 90s (paper here) and it really, really hurt. Additionally, “significant functional impairment of the hand persisted for three months”. So no need to try that at home people.

Foot spur! Copyright (c) 1995 E.Lonnon Wikimedia Commons

Foot spur! Copyright (c) 1995 E.Lonnon Wikimedia Commons

We don’t know if O. tharalkooschild was venomous, but we know that it was huge! This new species is described on the basis of one singular tooth. The beautiful part about mammalian teeth is that even one tooth can be so different than any other known specimen and it diagnoses an entire species.  When then-Honors student Rebecca Pian (now a PhD student at Columbia University/AMNH) was looking through the vast amount of fossil material from Riversleigh, she adeptly noticed that this monotreme tooth was not like the others. The tooth in question is a lower first molar, and based on its size, O. tharalkooschild was at least two times larger than its modern counter part Ornithorhyncus anatinus! An adult male platypus is ~50cm long, so O. tharalkooschild was at least 1 meter long!

Reconstruction of O. tharalkooschild by Peter Schouten

Reconstruction of O. tharalkooschild by Peter Schouten

Riversleigh, the fossil locality this specimen was discovered at, is a famous World Heritage site in the outback of Queensland, Australia. Some of the most spectacular fossil marsupials and monotremes that define the evolutionary history of Oz’s most iconic animals have been found here. Previously, the only fossil platypus known from Riversleigh was Obdurodon dicksoni and all vaguely platypus-y material was referred to that species.

The variation in morphology of this tooth really shakes things up in the world of monotreme relationships. All of the platypus relatives had very similar looking molars, indicating the evolutionary history of these animals was fairly simple. This big ol’ platypus throws a wrench in things—it is lacking twin lophs (ridges) on a certain part of the tooth, which indicates this is a separate radiation from the previously discovered modern and fossil platypuses.

The molar. Photo by Rebecca Pian.

The molar. Photo by Rebecca Pian.

The age of this specimen is a bit vague, based on current stratigraphic knowledge it could be middle Miocene (~15 Ma) or as young as Pliocene (~5 Ma). Either way, it is still an extremely unique specimen that changes what we know about fossil monotremes. The oldest fossil monotremes include animals like Steropodon and Kollikodon, both Cretaceous (~100 Ma) in age, from the Lightning Ridge locality in New South Wales, Australia. Besides being some of the oldest known monotremes, these specimens are unique because most of the fossils at Lightning Ridge are opalised—meaning the minerals in the bones and teeth have been replaced with shiny opal.

Steropodon opalised jaw. (c) Carl Bento Australian Museum

Steropodon opalised jaw. (c) Carl Bento Australian Museum

Besides the fossils I’ve mentioned, there are a few other fossil monotremes, but the record is relatively sparse. The origin of these animals is still a mystery, although the presence of yet another platypus relative fossil in Argentina (Paleocene in age) gives the indication there was, at one point, a Gondwanan distribution of these enigmatic creatures. Rebecca says “Other than the Patagonian platypus Monotrematum sudamericanum, we have nothing in between the early Cretaceous and the late Oligocene. No fossils have be found from Antarctica either despite evidence that they should be there.” There are a few fossil localities in Australia that seem promising for the discovery of monotreme teeth, so hopefully the record will be filled in in the coming years.

(This research is from an article in the Journal of Vertebrate Paleontology that is not yet available online)

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