Dean et al. (2017) Preservational Bias Controls the Fossil Record of Pterosaurs

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    Lisa Lundgren

    Recently the FOSSIL project social media team used Facebook and Twitter to ask what community members needed in terms of open access paleontology. The community’s feedback centered on holding discussions and receiving explanations on the scientific concepts found in open access papers. In this post (and in subsequent posts!) we’ll link to a specific paper and summarize it. We’ll also be hosting live discussions of papers, too, but that’s still in progress so stay tuned!

    For now, please jump into the forum posts with your interpretations of the papers we summarize.

    First up is a paper about pterosaurs. Click here for a link to it.

    The main point of the journal article:  Studying pterosaur fossils can help show preservational bias in the fossil record.

    Some key questions I ask when I read scientific papers: who, what, where, when?

    Who: Pterosaurs, which are *not* dinosaurs. They’re reptiles, and they’re the earliest vertebrates to have gotten powered flight.

    What: This paper is about preservational bias, which is related to taphonomy.

    Taphonomy is the study of how weathering and other processes affect fossils-it essentially asks, “what happens to an organism after it died but before its later discovery?” So preservational bias is the idea that not all organisms become fossilized in the same way or at the same rate. The authors also looked at “completeness” of each fossil specimen, which refers to the amount of fossilized material that can examined from that particular specimen.

    Where: Fossils found in lagerstatten (areas in the fossil record with really great preservation) throughout the world.

    When: The Mesozoic era, between 252 and 66 million years ago.

    To summarize the paper with main goals and findings:

    • Goals: To see if the “completeness” of specimens is related to “key” intervals of pterosaur history; and understand if “completeness” is a controlling mechanism for diversity
      • FINDINGS: “Completeness” of specimens does not limit understanding of taxonomic diversity nor does a lack of “complete” specimens relate to “key” intervals of pterosaur diversity
    • Goal: To see if lagerstatten impact pterosaur record
      • FINDING: Lagerstatten impact the pterosaur fossil record by inflating observed species diversity.
    • Goal: Compare preservation completeness of small bodied organisms and large bodied ones
      • FINDING: Completeness was different in small bodied organisms when comparing to large bodied organisms. This was especially true when looking at lagerstatten, where small bodied organisms tended to preserve more readily.

    Citation: Dean, C., Mannion, P., & Butler, R. (2017, October 16). Preservational Bias Controls the Fossil Record of Pterosaurs.




    Sadie Mills

    In the paper’s conclusion, the authors note that “The fossil record of pterosaurs is strongly and pervasively affected by Lagerstätten deposits and heterogeneous sampling, which consequently drives both observed pterosaur taxic diversity and completeness through time.” What are heterogeneous sampling techniques like within paleontology? Why do paleontologists use heterogeneous sampling strategies? Any ideas:  @vperez @mackenzie-smith @llundgren?

    MacKenzie Smith

    I think it’s just saying that pterosaur fossils get documented regardless of how they are preserved or where they are from. They are not a taxa that people tend to ignore. I feel like this is not entirely conscious since these specimens have been collected over hundreds of years but because they are large vertebrates people take interest in them. It’s heterogeneous because we are able to compile a large data set from multiple localities through the years.

    This brings me to another point – I think the “where” of this paper is actually online using the Paleobiology Database since that was how they compiled their data. Obviously, it takes fossils from the field to make this data set but the database is where the research was being done. I think it highlights the importance of open data and how not all paleontology is done in the field directly. A lot of our big picture concepts come from looking at large data.

    In terms of k-12, I remember reading a lot of peer-review papers in IB History classes and some in the natural sciences (since that was where my EE was in). Are there any IB Sci teachers that discuss peer review to answer @egardner ‘s question? If not I can share how we did it in history.

    Eleanor Gardner

    Late to the conversation on the pterosaur paper, @llundgren, my apologies.  Having done this type of review paper myself (but on the avian fossil record), I agree that a “Lagerstätten effect” likely impacts our understanding of many fossil taxa, including pterosaurs, birds, and amphibians.  It is not surprising that the statistical analyses in this study showed that completeness of specimens through time was influenced by Lagerstätten distribution.  However, because in my study I found that avian fossil specimens from Lagerstätten were much more likely to represent locations and time periods with warm and humid climates compared to cool and/or dry climates, I would be interested to know the climate data for the pterosaur Lagerstätten sites (many of which I’ll bet are the same as the bird sites).

    Also, an off-topic word of caution: the PaleobioDB is not error-free.  I found a variety of instances where formation, age, environment, or other information had been keyed into the database incorrectly.  That meant that my coauthors and I had the pleasure of carefully reading each of the 398 publications included in our study and making our own database (no small task!).

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