Publications from 2019

I was involved in some fun research that was finally published last year, and I didn’t have chance to write blog posts for all of it, so here’s a summary of what came out of the Falkingham lab last year:

The year started off with a paper led by collaborators at Brown.  My simulation work is an incredibly data-dense resource (every movement of every grain of sand in a footprint), and understanding that is not straight forward. The computer visualization experts at Brown have been using a Virtual Reality ‘Yurt’ to try and find new ways of exploring and understanding what’s going on when a virtual foot interacts with a virtual substrate. We published on this in the journal IEEE transactions on visualization and computer graphics.  Well outside the normal biology/palaeontology remit, but great fun nonetheless.

Figure 14 from Novotny et al 2019, showing the process of scientific sketching to produce VR visualizations.

This was followed up by a paper led by Dr Kristen Crandell, from Bangor University on the evolutionary relationship between morphology and drag reduction in the kingfisher family, published in Royal Society Interface. This was a really fun paper to be involved with, and I’m grateful to Kris for including me.  It’s a neat paper too, even if I say so myself – combining physical experiments with CFD simulations.

Figure 5.
Figure 5 from Crandell et al 2019, models and CFD domain for several kingfisher heads.

Two of my PhD students published the first papers from their PhDs this year too, which was great to see:

Pernille Troelsen (now Dr Troelsen, having successfully defended her PhD last year) saw her paper on plesiosaur hydrodynamics published, in which she led a team looking at just what effects the long neck in plesiosaurs might have had on their swimming performance. In light of plesiosaurs being extinct, and therefore being difficult to observe and measure, Pernille used CFD to simulate plesiosaurs swimming, changing neck length and curvature, and looking at the effects.  Her work was published in the Journal of Vertebrate Palaeontology.

Figure 1 of Troelsen et al 2019, showing how Nelly constructed her CFD plesiosaurs from figures of fossils.

Cat Strickson also so her first PhD paper published in the Journal of Anatomy.  Cat was exploring the relationship between under-foot area calculated using soft tissues, and also just bones.  Utilizing CT scans, Cat spent many months segmenting a whole bunch of scans of feet, and measuring the contact area they would have with the ground.  The result is a fairly consistent relationship between ‘skeletal area’ and ‘soft-tissue area’, but interestingly that relationship is different between the manus and pes – a really important finding in the context of the rest of her PhD. (Cat’s paper actually has a 2020 date now due to the nature of publishing)

Figure 2 from Strickson et al 2019, looking at how foot area differs if skeletons are used, rather than soft tissue.

Finally, just before the year closed out, a paper led by Prof Jim Farlow made it into the journal Ichnos.  This had been on the burner for a while, first submitted well back in 2018. It was a cool description of a site in Texas with manus-only sauropod trackways.  I had some really interesting conversations with Jim about how the tracks were formed, and we went back and forth between punting sauropods and variable underfoot pressures.  I think in the end, we have a really thorough paper exploring a whole bunch of data to interpret a site.

A cast of one of the sauropod tracks from Coffee Hollow, captured with photogrammetry

It wasn’t a mind-bendingly productive year, and I’m disappointed that I didn’t get a first author paper out (I like to aim for at least 1 or 2 per year).  There’s a couple of manuscripts currently sitting at the review/revision stage that I’m really excited about, particularly a couple that continue analyses of XROMM data collected 5-6 years ago now, but we’ll have to see how 2020 goes.

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  1. I thought you might be interested to know that animal weight, can be derived from (typically) one rear footprint surface area using approximately 5,000 lbs per square foot of rear foot print surface area. The Limitation is the ultimate bearing capacity of soft soils, and how far the animal is allowed to sink into the mud until a layer is reached where the soil will no longer displace vertically, and is confined laterally, and will support the animal. If the animal sinks some but not up to its belly, it survives to reproduce. If its feet are too small for its leg length, it gets stuck, bellows, and gets eaten. If its feet are too big for its leg length, then the pendulum actions make it slower than its friends, it ends up last in a race, and it gets eaten. The result of this is evolution toward the smallest allowable feet for the fastest large animal that just will not quite get stuck in the mud as it crosses a river.

    The Large footprint at Dinosaur Ridge, Dakota Ridge, Morrison Formation, Colorado at about 148 Ma has a single rear footprint surface area of about 4.43 SF, multiplying by 5,000 gives a max weight of around 22,150 lbs. The distance between the Right Rear footprint and the left rear footprint was about 10.95 feet, which gives an estimated leg length of between 13 and 14 feet to the rear hip socket, and around 20 feet to the hump on the animals back over the hips. Animals walking thru and sinking into mud 30 to 40 inches have longer than normal stride lengths , so the interior angles of 75 degrees, and 75 degrees with a diagonal base length of 10.95 feet do not apply. It is closer to , but not nearly at an equilateral triangle, of 60 degrees. It was closer to around 65 degrees, but who knows.

    The guess is around 60 feet long, and the age was like that of a teenager as its feet were way too small to be a full grown adult. The Largest full grown adult footprints are around 4 foot wide and 5 foot long oval , and around 15.9 SF of one rear footprint surface area. 15.9 X 5,000 = about 79,500 lbs.

    Note that 22,150 / 79,500 = 27.86 % of the maximum allowable sauropod weight.
    Taking the cube root of 0.2786 = 0.6531 or about 65.31 % of the maximum length for the time period of 148 Ma. 0.6531 X 90 = 58.78 feet long ( minimum ).

    Occasionally someone will make a statement that a sauropod weighed 190,000 lbs.
    This was never physically possible, they always were less than 80,000 lbs in all time periods. A 190,000 lb sauropod would require a single rear footprint surface area of
    38 SF. Footprints of this size have never been found, and will never be found. But you can make an educated guess as to how big it was but using ratios. 15.9 / 38 = 0.41842.
    0.41842 X 2200 = 920.5 lbs of water weight in the time period that the animal lived.
    This would barely let the animal swim with its head above water.
    79,500 / 920.5 = 86.366 cubic meters of maximum volumetric displacement.

    86.366 / 5.84255 = 14.78 224405 Male African Elephant Volumes.

    ( 14.78224405 )^(2/3) = 6.0232 Surface areas.
    6.0232 / 14.78 224405 = 0.40746 g
    Note that since the calculated surface gravity is just less than the supposed 190,000 lb
    surface gravity, of 0.41842, the actual animal could have been just slightly bigger when it died, but it still would never get over 79,500 lbs, and it still would never displace over about 89 cubic meters, and the lowest water weight was around 892 lbs per cubic meter, and the lowest surface gravity was about 0.405480 g. The 920 lbs is more characteristic of the time period where most Morrison Formation Dinosaurs were found. Roughly around 150 million years ago, rather than the maximum size at 167 million years ago, and
    a lowest water weight of dinosaurs of 892 lbs per cubic meter.

    Animals got smaller this side of 167 million years ago, generally.

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