2017 Hurricane Season Changes Lizard Population in Turks and Caicos

Hurricane-induced selection on the morphology of an island lizard
Colin M. Donihue, Anthony Herrel, Anne-Claire Fabre, Ambika Kamath, Anthony J. Geneva, Thomas W. Schoener, Jason J. Kolbe & Jonathan B. Losos

What data were used? Individuals of Anolis scriptus were captured and specific measurements (such as total length, length specific bones, longest toe on fore- and hindlimb, area of toepad) were taken of each lizard along with pictures. In the initial survey study, 71 lizards were captured and measured and in the post-hurricane study, 93 lizards were examined.

Five lizard individuals undergoing the wind behavior experiment. In the first frame for each lizard you can see that they all have the same perch tactic on the dowel as the leaf blower is turned on. By the second or third frame, it is observed that their hindlimbs are starting to have air flow under them and by the third or fourth frame their back legs have completely detached from the perch. These are the lizards that were captured after the hurricanes occurred and have larger toepads and decreased femur lengths.

Methods: After taking measurements of all lizards, a multivariate analysis of covariance was completed. This type of analysis is used when a question has many variables (in this case all of the different measurements) and you want to know if there is a significant difference between the measurements. So the researchers in this case wanted to know how different the measurements taken before Hurricanes Irma and Maria were from the measurements taken after. In addition to this statistical analysis, a behavioral study was completed to see how the observed changes in predominant body type were beneficial in withstanding hurricane force winds. This elegant study was comprised of placing a lizard on a wooden dowel surrounded by a net and padding to catch the lizard as it was blown off the dowel. A leaf blower was then turned on and “wind speed” gradually increased until the lizard could no longer hold on to the dowel.

Results: After completing the statistical analyses, it was found that the morphologies (shape) of A. scriptus on these two islands were significantly different from the morphologies of the individuals measured prior to the hurricanes. Two of the most notable changes was the increase in size of toepads on both the fore- and hindlimbs, and the decrease in femur (thigh bone) length. These changes in morphology are what led the researchers to predict that these surviving lizards had a better clinging ability. The results of the wind behavior test show that all lizards clung to the dowel in the same way with their femurs jutting out. As wind speeds increased the hindlimbs lost their grip on the dowel first, suggesting that their hindlimbs catch wind and ultimately pull them off of their perch.

Why is this study important? This study is important because Anolis lizards are known to be good examples of adaptive radiation (evolving to be better suited for many different ecological roles) and this is the first study where researchers were able to study two populations immediately preceding and shortly after two hurricanes devastated the islands they initially studied.

The big picture: Big picture, this study is important to understanding how small island populations react to severe weather events. The researchers were able to determine that this was a natural selection event because even though there was variation in morphologies, the trends all show this shift to being better suited to hold onto a perch in high winds. The next question that is addressed in this paper is whether or not this will be a permanent adaptation or if the previous level of morphological variation will be able to return. The answer to this question lies with the lizards just as much as it lies with climate change. As the Earth’s climate continues to warm and weather events continue to become more extreme and more frequent, researchers and inhabitants of these islands may see permanent shifts in the morphologies of the organisms on these islands as they adapt to be able to survive these weather extremes.

*All lizards were returned to their habitats unharmed after their capture and the following experiments*

Citation: Donihue, C. M., A. Herrel, A. Fabre, A. Kamath, A. J. Geneva, T. W. Schoener, J. J. Kolbe, J. B. Losos, 2018. Hurricane-induced selection on the morphology of an island lizard. Nature, 1-8. Data from study.

New plesiosaur fossils from Antarctica

The first non-aristonectine elasmosaurid (Sauropterygia; Plesiosauria) cranial material from Antarctica: New data on the evolution of the elasmosaurid basicranium and palate

 O’Gorman, J.P., Coria, R.A., Reguero, M., Santillana, S., Mörs, T., Cárdenas, M.

What data were used?

New fossil material from Vega Island in Antarctica


The fossils were prepared using tools like a jackhammer to remove the fossils from surrounding rock. The fossils were then measured using digital calipers.


Rare fossil material recently found from Vega Island in Antarctica shed light on the evolutionary relationships of extinct reptiles, the plesiosaurs. While a lot of plesiosaur material has been found in the past in Antarctica, this particular field study turned up skull material, which is quite rare! The skull material preserved multiple features that allowed researchers to better understand the evolutionary relationships between different groups of plesiosaurs. Specifically, features of the palate in the skull, has features that link it to other groups of plesiosaurs, the elasmosaurids.

A representative of the specimen uncovered from Vega Island. Shaded in gray are the bones uncovered, including a rare example of a bone from the skull, preserving the palate of the plesiosaur!

Why is this study important?

This study is important for many reasons! First, it described very rarely preserved parts of the body (namely, the skull), which preserves a ton of information about its evolutionary origins. Second, Antarctica remains very unexplored for fossils; it is very expensive and difficult to travel and do field work in this part of the world. This means that with every new fossil find, our knowledge of the past history of Antarctica grows tremendously!

The big picture

New fossils from Antarctica provide new information concerning the biodiversity and evolutionary relationships of plesiosaurs from the Cretaceous. As Antarctica remains fairly unexplored for fossils, any new fossil finds contribute greatly to our knowledge of the history of the continent.


O’Gorman, J.P., Coria, R.A., Reguero, M., Santillana, S., 2017, The first non-aristonectine elasmosaurid (Sauropterygia; Plesiosauria) cranial material from Antarctica: New data on the evolution of the elasmosaurid basicranium and palate: Cretaceous Research, v. 89, p. 248-263, doi: 10.1016/j.cretres.2018.03.013

Something seems fishy here…warm blooded fish?

Whole-body endothermy in a mesopelagic fish, the opah, Lampris guttatus

Wegner, N.C., Snodgrass, O.E., Dewar, H., Hyde, J.R

Lampris guttatus, a fish who is able to produce its own body heat! (Source: fishbase.org). This fish is found worldwide, though it’s especially common in Hawaii and west Africa.

What data were used?
Captured and freely-swimming opah fish

Researchers measured the body temperatures of captured and freely swimming fish at their natural depth. Temperatures were taken in multiple places along the fish, including the temperatures of a number of the muscles. These measurements were taken by heat monitoring sensors placed in the muscles of the fish.

Researchers found that the core of the fish (pectoral muscles, heart, etc.) were much warmer than the surrounding environment. The cold, oxygenated blood of the fish is warmed by the conducting of heat from the warmer, deoxygenated blood leaving the respiratory system before the oxygenated blood reaches the respiratory system. This indicates that these fish, just like humans and all other mammals, are able to produce their own body heat (“warm blooded”) as opposed to creatures like reptiles, who rely on external sources, like the sun, to maintain their temperature (“cold blooded”).

Why is this study important?

The temperature of an opah fish as taken by the scientists of this study. Measurements were taken ~4-5 cm below the skin of the fish for 98 cm, the length of the fish’s body.

We’ve all learned from school that critters like reptiles and fish are cold blooded, whereas mammals (like us) are warm blooded. Simple, right? It turns out, it’s not nearly as simple as that! More and more, scientists have begun to discover that there are many animals that don’t fit into these neat categories, the opah fish being the most recent of these. This is important because in the fossil record, we don’t have the luxury of examining animals while they’re still alive, so we need to look for other clues! Dinosaurs and pterosaurs are excellent examples of this-we’ve always thought reptiles were cold blooded. But dinosaurs, like Velociraptor, had feathers! They had larger brains! Pterodactyls could fly by flapping their wings! All of these are examples of warm-blooded behavior. Fish like the opah show us how what we thought we knew might not always be the case!

The big picture
The picture that I want to stress here is that even the big things we thought we understood in science-like who’s warm and cold blooded-are subject to change with new data! Only within the last few decades have scientists begun to ditch the idea that animals fall neatly into categories of “warm” and “cold” blooded. It’s also important to note that discoveries such as these open our interpretations of extinct organisms-like dinosaurs, pterosaurs, and yes, even fish!- and how they were able to generate energy. Since we can’t bring a live pterodactyl (at least, not yet! Maybe we’ll learn more after watching Jurassic World: Forgotten Kingdom) in for testing, data such as these remind us that life isn’t as simple as just ‘warm’ and ‘cold’ blooded.

Wegner, N.C., Snodgrass, O.E., Dewar, H., Hyde, J.R., 2015, Whole-body endothermy in a mesopelagic fish, the opah, Lampris guttatus: Science, v. 348, p. 786-789, DOI: 10.1126/science.aaa8902

Mosasaurs preying upon echinoids

Eggs for breakfast? Analysis of a probable mosasaur biting trace on the Cretaceous echinoid Echinocorys ovata Leske, 1778

Christian Neumann and Oliver Hampe

What data were used?

The authors examined over 7000 specimens of Echinocorys for this study. Echinocorys is an extinct (no longer living) group of echinoids, commonly known as sea urchins or sea biscuits! Specimens were obtained from field excursions by the authors as well as examination of multiple museum collections. From examining such a large number of specimens they were able to identify many different types of predation traces but focused on the extraordinary bite traces for this study.


Each of the tooth imprints was measured as well as careful measurements of the test (body) of Echinocorys. Images of the trace (tooth imprints) were taken at various angles to visualize the structures in greater detail. A bite experiment was conducted by creating resin models of possible predator skulls with movable jaws. The skull could then simulate biting into modeling clay versions of Echinocorys. The resulting traces were measured and compared to those found in the real samples of Echinocorys.

Results and Discussion

Figure containing the images of the bite marks on the echinoid. The top part of the echinoid was not preserved so we are seeing the bottom side only, note the anus has been labeled and is not one of the punctures! (c) shows us the fine detail of where the echinoid healed the puncture wounds!

The results of this study indicate that the biting trace pattern was produced by a predator with large cone-shaped teeth that were arranged in a forward pointing direction. This was interpreted from the strange pattern in the traces. Two bite punctures are smaller and oval in outline where as two others are circular and larger, this is likely due to the angle at which the teeth made contact with the echinoid test (body).

The fact that the bite did not destroy the echinoid skeleton is quite interesting and could be interpreted as the attacker’s skillful prey handling and biting mechanics. Also, echinoid tests are very well structured, built from a series of meshwork structures that help reinforce the skeleton. This makes echinoid tests more difficult to crush compared to other invertebrate organisms such as snails or clams. Even though this echinoid sustained large punctures, it was able to begin to heal as evidenced by the newly developed skeletal material within the punctures seen in the figure above. This is not uncommon in echinoderms and has been well documented through time, quite amazing creatures!

The authors compared the bite punctures to other known predation traces in echinoids and found that it was not similar to those previously documented. They made comparisons to teeth shape, size, and when specific animals lived to attempt to identify the maker of these traces. The authors then used experimental methods with their resin models and clay-modeled echinoids to better determine the probable trace maker and found that it is most likely a globidensine mosasaur. This is from the teeth shape, pattern, time period they lived in, and experimental method to indicate the angle of teeth as they penetrated the echinoid.

This figure shows us the detail of the forward facing teeth matching up with the punctures on the echinoid test (body). In (c) we see the part of the echinoid not preserved in the fossil record.

Why is this study important?

This study represents the first likely record of mosasaur predation on echinoids. Mosasaurs were apex predators but were also opportunistic predators, as evidenced by this study. They didn’t just eat the most filling prey but also nibbled on those smaller animals that were shelly and lived on the seafloor.

The big picture

Predator-prey interactions can be observed today in a variety of environments and habitats but in the fossil record we are limited by what ecosystem interactions are preserved through time. Trace fossils are particularly useful in gaining a better understanding of how organisms interacted with one another in the past! It’s often quite difficult to gain a full understanding of the organism that left the trace since all we have is evidence of the behavior but this work provided a thorough examination of possible trace makers and even provided an experimental test to further support their idea!


Neumann, C. and Hampe, O. 2018. Eggs for breakfast? Analysis of a probable mosasaur biting trace on the Cretaceous echinoid Echinocorys ovata Leske, 1778. Fossil Record, v. 21, p. 55-66, doi: 10.5194/fr-21-55-2018

Are corals adapting to keep up with changes in ocean temperature?

Potential and limits for rapid genetic adaptation to warming in a Great Barrier Reef coral

Mikhail V. Matz, Eric A. Treml, Galina V. Aglyamova, Line K. Bay

What data were used?

Researchers looked at genetic data for Acropora millepora (coral common in the Great Barrier Reef) to model (simulate) how corals will adapt to increasing temperatures, establish a direction of coral migration, and measure genetic diversity. These data were then used to predict the future survival of A. millepora in the Great Barrier Reef.


The corals used in this study were previously described in van Oppen et al. (2011) and several samples were collected from Orpheus and Keppel Islands. The coral samples were then genotyped (the genetic material was sequenced so that researchers could examine it) and that data was used to model all of the other experiments that were conducted. The coral genomes were used to look at divergence between populations (how genetically different are the populations that were sampled) and what are the demographics among populations. A biophysical model was used to examine the migration patterns between known coral habitats and the broader region surrounding the Great Barrier Reef. This model required data describing the seascape environment as well as coral-specific data relating to adult density (how many adults), reproductive output and larval spawning time, as well as how far do the larvae travel or disperse.


Figure 1. A. A map of the coast of Australia and the locations along the Great Barrier Reef that coral samples were taken from. A temperature gradient is also plotted on the map, with warmer colors indicating warmer temperatures and cooler colors indicating cooler temperatures. B. A plot of the different water conditions that were measured for each study site and where each study site plots in relation to those water conditions. C. A plot of how similar each coral population was to one another. The separation of the purple dots indicates that it is more genetically separated from the other coral populations that were sampled. D. This plot further shows that the population at Keppel is more genetically distinct from the other groups as the proportion of blue to yellow is drastically increased.

The results of this study indicate that the populations examined are demographically different from one another and that overall migration of these corals is moving in a southward direction (higher latitudes). The migration southwards is still largely driven by ocean currents, rather than preferential survival of warm-adapted corals migrating to cooler locations. It was also determined through the model that those corals that were pre-adapted to a warmer climate, were able to survive gradual warming for 20-50 generations which equates to 100-250 years. However, as the temperature increased, the overall fitness (the ability of a species to reproduce and survive) of these populations began to fluctuate with random thermal anomalies (e.g. El Nino Oscillations) and these fluctuations in fitness continue to increase as warming progressed, independent of the severity of the thermal anomalies. The good news in all of this is that much of the variation in the trait associated with the ability to adapt to warmer temperatures is due to the type of algal symbionts (algae that helps the coral to survive and reproduce) in the area. This means that coral larvae have very plastic (easily changed) phenotypes (genes that are visibly expressed) and can easily adapt to whatever algal symbionts are locally available.

Why is this study important?

This study is important because it has been projected that the global temperature is going to rise 0.1°C per decade for a total of 1°C in the next 100 years and as scientists we want to know how that global temperature change is going to affect organisms. Corals function as a “canary in the coal mine” because they and their algal symbionts are incredibly sensitive to temperature and light changes in the ocean. If we know how corals are going to respond to these changes in temperature, researchers and conservationists will have a better understanding of how to better protect the coral’s environment. This study has shown that corals are able to adapt to the changes in temperature and are migrating southward, but also demonstrated that the ability of mature corals to reproduce in rising temperatures is declining. To combat this, because of this study, conservationists know and may be able to release larval and juvenile corals that have been raised in labs into new environments to perpetuate the species.

The big picture

The big picture here is that climate change is very real and we can use evolution and models of evolution to understand how organisms are going to and are reacting to increasing temperatures. This research indicates that even with low levels of mutation, corals are able to adapt to warming oceans and can associate with different, local algal symbionts as they migrate. However, mature adult corals have increasingly less fitness as ocean temperatures rise which means that they are reproducing less, leading to overall decreased coral populations. There is hope for this particular coral though, if researchers and conservationists can find a way to successfully raise coral larvae and release them into their current and future habitats.

Matz, M. V., E. A. Treml, G.V. Aglyamova, L. K. Bay, 2018. Potential and limits for rapid genetic adaptation to warming in a Great Barrier Reef coral. PLOS Genetics, 14:4:1-19, doi: 10.1371/journal.pgen.1007220

Geologic evidence for changes in paleoclimate on Mars

Dichotomies in the fluvial and alluvial fan deposits of the Aeolis Dorsa, Mars: Implications for weathered sediment and paleoclimate

Robert E. Jacobsen and Devon M. Burr

What data were used? In this study, the scientists used images and topographic data from satellites orbiting Mars. This data was collected using two instruments:

CTX (Context Camera) images from the Mars Reconnaissance Orbiter were used to map the locations and types of fluvial and alluvial (formed by flowing water) geologic features in the study area. Images from this camera can resolve features about the size of a room (5-6 m or 15-20 ft).

MOLA (Mars Orbiter Laser Altimeter) topographic data from the Mars Global Surveyor was used to find elevations of the different features that were mapped and infer their relative ages. For example, if one feature is on top of another, the higher one is inferred to be younger.

Methods: The authors made a geologic map of the Aeolis Dorsa region using images from thes two datasets described above. The Aeolis Dorsa region is a rectangular area roughly 500 x 500 km. There are many types of sinuous (snake-like) ridges in this area that were formed by wind depositing or eroding the sand and rocks, by flowing water, or by tectonics. Some of these sinuous ridges are interpreted by geologists as inverted fluvial and alluvial deposits. Fluvial refers to transport by rivers or streams and alluvial refers to transport by intermittent water, such as on a floodplain. These types of features are formed by water carving out a river channel and depositing rocks and sediments within that channel. When the water dries up, these rocks and sediments become hardened by a process called chemical cementation, which means the rocks and sediments are “glued” together chemically by minerals dissolved in the water. Later, the rocks around these indurated sediments are eroded and what was a channel now appears as a ridge. This enables geologists to use the inverted channels to map out ancient river deposits.

Map of the Aeolis Dorsa region with colors showing different topographic elevations. The red and brown are higher elevations and blue and green are lower. The brightly colored lines represent the different types of fluvial and alluvial features that were mapped, and the black boxes are smaller areas studied in detail.

Results: The locations and relative ages (which deposits are older than each other) of the inverted channels found in the Aeolis Dorsa region show two things. First, the deposits in the southern part of the region required more water and mud to form, implying that there was more rain and more cohesive (“sticky”) soil good for making mud in the south than in the north. Second, the amount of precipitation evolved over time. The older deposits were mainly fluvial and required more water/precipitation than the younger deposits which were mainly alluvial.

Why is this study important? This study is important because it shows how the climate varied over time and within different areas of the same local region on Mars. The study also used terrestrial analogs, which are places with similar features on Earth. This is important because we can’t yet go to places on Mars and directly sample the rocks, so scientists use these terrestrial analogs that they can directly sample to compare what they see in the geology of Mars.

The big picture: Understanding the local variations in paleoclimates on Mars is important to scientists because studying the past climate of Mars can tell us about past “habitability” – the availability of water and other resources for life. Studies like these can also help scientists find good places to land and explore further on future missions to Mars.

Citation: Jacobsen, R. E., and Burr, D. M., 2017, Dichotomies in the fluvial and alluvial fan deposits of the Aeolis Dorsa, Mars: Implications for weathered sediment and paleoclimate: Geosphere, v. 13, no. 6, doi:10.1130/GES01330.1

What does climate change mean for New York City?

Impact of climate change on New York City’s coastal flood hazard: Increasing flood heights from the preindustrial to 2300 CE

Andra J. Garner, Michael E. Mann, Kerry A. Emanuel, Robert E. Kopp, Ning Lin, Richard B. Alley, Benjamin P. Horton, Robert M. DeConto, Jeffrey P. Donnelly, David Pollard

Data and Methods: This study employs various models to understand the future impact of climate change from tropical cyclones. These cyclones create storm surges, which are abnormal rises in water that often lead to flooding. To model storm surge heights in the past (1970-2005), this study uses data from about 5,000 storms. For predicting future storm characteristics for the next few centuries, the study assesses about 12,000 storms. Researchers use storm data to run a variety of simulations that have varying parameters. For example, they can modify the trajectories and wind speeds of tropical cyclones, and the frequencies and intensities of storms to model different scenarios.

They then used the storm models to quantify potential flooding in New York City by combining estimates of storm surge heights with anticipated sea level rise. Such changes in sea level are governed by mass loss of glaciers and ice sheets, thermal expansion, ocean dynamics, and water storage on land. Again, they modified these parameters in a number of models to predict flooding from future storm surges. This study focuses on two specific scenarios from previously developed models: Representative Concentration Pathway (RCP) 4.5 and 8.5. Various modifications to RCP4.5 and RCP8.5 are used to make predictions about the future of storm-related flooding in New York City.

FIgure 1. Projected sea level rise from present day to 2300. Climate projections RCP4.5 (yellow) and RCP8.5 (orange) have much lower projections than the red and maroon projections that represent enhanced Antarctic Ice Sheet melt. By 2300, sea level near New York City could rise by a maximum of 15.7 meters (51.5 feet).

Results: This group found that the maximum wind speeds of tropical cyclones in the future are much greater than the maximum speeds we see today. From this they conclude that future tropical storms will be much more intense, and the storm surges that reach New York City will be greater. They also found that the tracks of tropical cyclones will shift with time, and the density of tracks near New York City will increase.

For the next century, this study estimates sea level rise for New York City to be between 0.55 and 1.4 meters (Figure 1). From 2100 to 2300, they predict possible rises of 1.5 to 5.7 meters. If they increase the potential ice loss from the Antarctic Ice Sheet, those values drastically increase to a maximum sea level rise of 15.7 meters by 2300. Remarkably, these values simply estimate relative sea level rise without the added effect of storm surge. Toward the end of this century (2080 to 2100), flood heights are expected to be 0.7 to 1.4 meters higher than modern New York City floods (Figure 2). By 2300, storm surges could cause floods that are 2.4 to 13.0 meters higher than modern values.

Figure 2. These four different models show flood height versus density. Each model compares modern heights to RCP4.5, RCP8.5, and both scenarios with enhanced Antarctic Ice Sheet melt. With all models and all scenarios, the average flood height is expected to increase.

Why is this study important? At present, an increase in the intensity and frequency of storms would have a negative effect on coastal zones like New York City. However, in a future with higher sea levels, the effects of tropical cyclones and storm surges could be catastrophic. Continued emissions of greenhouse gases, rising temperatures, and consequential melting of ice will create a future with significantly higher sea levels. As storms develop and create surges of higher water, their resulting floods will be larger than anything New York City–or any other city–has seen before. Comprising of nearly 50 million built square meters and over 8 million people, this coastal city is a climate change target. The hazards associated with sea level rise in such a large and populous area are unimaginable. This study only looked at the effects on this one city; but there are places around the world that risk losing everything to climate change and sea level rise.

The big picture: Sea level will rise as human-driven climate change continues to warm global temperatures and melt ice sheets. The combined effects of higher sea levels and more intense tropical cyclones will create storm surges with the potential for catastrophic flooding in major cities like New York.

Citation: Garner, A.J., Mann, M.E., Emanuel, K.A., Kopp, R.E., Lin, N., Alley, R.B., Horton, B.P., DeConto, R.M., Donnelly, J.P., and Pollard, D., 2017. Impact of climate change on New York City’s coastal flood hazard: Increasing flood heights from the preindustrial to 2300 CE. PNAS. DOI: 10.1073/pnas.1703568114

New echinoderm fossils from Anticosti Island, Quebec

Late Ordovician (Hirnantian) diploporitan fauna of Anticosti Island, Quebec, Canada: implications for evolutionary and biogeographic patterns

Sarah L. Sheffield, William I. Ausich, Colin D. Sumrall

What data [were] used? New fossils found from Anticosti Island in Quebec, Canada.

Methods: New fossils of poorly understood echinoderm (relatives of sea stars) fossils discovered from Upper Ordovician (445-443 million years ago) rocks were analyzed and compared with middle Silurian (434-428 million years ago) to better understand biogeographic and evolutionary trends.

Results: The Holocystites Fauna is a group of poorly-understood diploporitan echinoderms (a term that just means they breathe out of sets of double pores found on their body) that scientists assumed to have only lived in the midcontinent of the United States (e.g., Tennessee, Iowa, Indiana, etc.) during a very specific time within the Silurian. New fossil species Holocystites salmoensis, however, tells us that they actually also lived during the Late Ordovician of Canada, which extends their known range nearly 10-15 million years!

This fossil of Holocystites salmoensis represents a very important new datapoint that helps scientists understand poorly known echinoderm transitions from the Late Ordovician to the Silurian. A. The mouth area of Holocystites salmoensis. B. a close up of the diplopore respiratory structures. C. A line drawing of the mouth area of Holocystites salmoensis. D-E. Other fossils of Holocystites salmoensis and (F) an unidentified diploporitan found in the same deposit (Sheffield et al., 2017).

Why is this study important? So at first glance, this paper might not seem so important-it’s just one new fossil of a relatively rare group of echinoderms. What is so important about this is the time in which these fossils were found. Rocks from the Upper Ordovician, during which this fossil was found, are very rare because the ocean levels were very low. Earth was in an ice age, so a lot of ocean water was taken up in glacial ice. When sea levels are low, fewer rocks are preserved; therefore, fossil data from low sea levels are rare. Evolutionary transitions of fossils from the Ordovician through the Silurian aren’t well understood. Now that we’ve found evidence of Ordovician Holocystites, we can infer a lot more about when and how these organisms evolved.

The big picture: Crucial information about how life on Earth evolved is often hard to find from times like the Late Ordovician. Actively searching for rocks during these times and identiying fossils from within them can tell us a lot about how past life responded to mass climate change (like ice ages and significant warming periods). It can also tell us a lot about how organisms expanded and shrunk their biogeographic range. Even one new fossil, like the one identified in this paper, can change a lot about what we think we knew!

Citation: Sheffield, S.L., Ausich, W.I., Sumrall, C.D., 2017. Late Ordovician (Hirnantian) diploporitan fauna of Anticosti Island, Quebec, Canada: implications for evolutionary and biogeographic patterns: Journal of Canadian Earth Sciences, v. 55, p. 1-7, doi: 10.1139/cjes-2017-0160

New data suggests Louisiana coast is sinking at an accelerated rate

A new subsidence map for coastal Louisiana
Jaap H. Nienhuis, Torbjörn E. Törnqvist, Krista L. Jankowski, Anjali M. Fernandes, and Molly E. Keogh

Data: Data for this study was collected by another study (with a lot of the same authors) by Jankowski et al. (2017). The data is small-scale changes in wetland surface elevation – this simply means how high or low the wetland is compared to the water table.

Methods: These authors used a new technique through the Coastwide Reference Monitoring System (CRMS) program. They used long steel rods called surface-elevation-marker horizon records – in this case these rods had been in place for 6-10 years and allows the scientists to calculate how quickly the coastline is sinking (sinking of land is called subsidence). This working group also used GPS time series (data from GPS collected over a period of time) of stations below the land surface to capture deeper sinking.

Results: Their results are clearly visualized in the map of the coastline. The results indicate that there is a widespread area of subsidence (sinking) recorded at the land surface and that the rate of sinking is relatively uniform across coastal Louisiana. The results presented in this study are considerably higher than in other recent studies that have used other methods.

This subsidence map for the coastal Louisiana area is based on observational data (all of the black dots) for the last 6-10 years. The areas that are in white or gray were excluded from the analysis. These areas are either cities or agricultural areas, which have modified drainage systems (such as underground sewer systems). The warmer colors indicate increased rates of subsidence. 

Why is this study important? The gulf coast has experienced substantial wetland loss. These low-elevation coastal zones (LECZs) are very sensitive regions considering the recent rises in sea level, which are driven by the increasing climate change. In order to understand the acceleration of wetland loss, it is important to understand what has happened in the recent past. Scientists can then use this data to predict the migration of the coastline and help prevent damage and loss of life.

The big picture: These new techniques for exploring data in low-elevation coastal zones can now be applied to other locations in the world. With more scientists exploring changing coastlines, there will be a greater understanding on how sea-level rise will affect humanity in the near future.

Citation: Nienhuis, H. J., Törnqvist, T.E., Jankowski, K.L., Fernades, A.M., and Keogh, M.E. A new subsidence map for coastal Louisiana. GSA Today, vol. 27. DOI: 10.1130/GSATG337GW.1

How Did Horses Get to Just One Toe?

Mechanics of evolutionary digit reduction in fossil horses (Equidae) *
Brianna K. McHorse, Andrew A. Biewener, Stephanie E. Pierce
Summarized by Time Scavengers contributor, Maggie Limbeck

What data were used? This study used metapodials (toe bones) from 12 fossil horse genera as well as from a tapir (herbivorous mammal that looks similar to a pig, but that also has an odd number of toes) to collect data. The metapodials were imaged in cross sectional views to determine load strength (how was weight distributed among the main three toes of fossil horses and the one toe of recent horses) and geometry of the metapodials.

Methods: The metapodials from the fossil horses and tapir were micro-CT scanned (3D x-ray scanning, like the human procedure but on a smaller scale) and the images were manipulated to see the cross sectional area and other views using the open source program ImageJ with the plugin BoneJ. The images were then measured and corrected for evolutionary changes using the open source statistical software, R. Estimates for bone stress were calculated using a toe reduction index (TRI), reconstructed body weights, and angle of metapodial during ground reaction at two speeds of forward locomotion. Additionally, the amount of stress that the metapodials could support was estimated using beam mechanics (an engineering process that looks at how much stress a hypothetical beam could withstand before bending and/or breaking).

Results: Looking at the geometry of the metapodials, it was determined that as the fossil horses grew in both size and weight, their need for four front and three back toes was decreased, and as such the digits gradually decreased to one on all four limbs. For the stress experiments, as the fossils moved forward in time to recent horses, it is seen that the amount of stress that can be placed on metapodial III (what we see expressed as the hoof) increases through time and the dependence on the two metapodials on either side of digit III decreases. This statement is true for both front and back metapodials at both a moderate speed (trotting) and performance (acceleration, jumping).

Figure 1. Image of the toe reduction index (TRI) shown across a phylogenetic tree (evolutionary tree) with the cross sectional view of the metapodial being analyzed. Based on the TRI it is apparent that there is a gradient for toe loss and that there is only one genus of horse, Equus, that truly has one toe. You can also see that for those early horses that still had side toes that the shape of the toe in cross section has a much different shape and therefore still needs side toes to some extent.

Why is this study important? This study is important because it supports two hypotheses that were held about digit reduction in horses. That a) the increased body mass of horses selected for a single, strong metapodial and b) that as horses grew taller, the cost of speed from the side toes outweighed their use in stabilization. This also contradicts the commonly held belief that horses experienced digit reduction as an adaptation to the replacement of forests by grasslands.

The big picture: The big picture here is sort of two-fold. Digit reduction in tetrapods (four-legged creatures) has been of interest to many scientists because as tetrapods emerged onto land 5, 8, even more digits was the ancestral state for these organisms. As we see today, that is not the case. The vast majority of the organisms that we think of have 5 or less digits on their hands and feet, so we want to understand what drove the process of digit reduction in every animal. Second, this study highlights that it is important to keep testing hypotheses even if they have been held for a while. The additional lines of evidence provided by this study give more credibility to two commonly held hypotheses while continuing to falsify the common explanation for digit reduction in horses.

Citation: McHorse BK, Biewener AA, Pierce SE. 2017. Mechanics of evolutionary digit
reduction in fossil horses (Equidae)
. Proceedings of the Royal Society B 284: 20171174.

*all samples in this study were fossils, no live animals were used