USF Paleo/Strat

New spider family discovered in Europe

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First Record of the spider family Hersiliidae from the Mesozoic of Europe

Summarized by Devan Legendre, a geology major at the University of South Florida. He is currently a senior in his last semester. Once he earns his degree, he plans to work in the geotechnical industry and gain experience to actively promote himself within the field. When he’s not studying geology, he enjoys running long distances to clear his head and gain new insight. 

Hypothesis: The aim of this study is to describe a new male spider found in ajkaite (sulfur-bearing resin found in brown coal) from the Ajka Coal Formation in Hungary and place the male spider in a new taxonomic group. The climate and the environment in which the resin was found was used to evaluate the current environmental description for the Ajka Coal Formation and better predict past environments. 

Data used: Arachnid fossils that are found preserved in amber resin offer a unique glimpse into the build of arachnid fossils, which usually don’t have their legs preserved.  The amber provides a preservation that is often entirely complete, shows the entire body build, and has a level of detail not often found in other methods of preservation for fossils. This can also help to understand the behavior and ecology of arachnids. The amber fossils used in this study are from the Ajka Coal Formation in Hungary that is one of two areas known for Mesozoic amber inclusions dated between 86 to 83 million years of age.

Methods: The chunk of ajkaite resin for this study was almost completely opaque, making it too dark for examination by light microscope. An X-ray tomograph from the University of Pannonia in Veszprem, Hungary was used to scan the large chunk of ajkaite. Upon scanning, multiple arthropod inclusions were discovered inside the chunk, including a relatively large sized spider. To achieve a better resolution scan on the spider, the ajkaite was broken to a smaller size for easier scans. A micro-computed tomography scanner in Hamburg, Germany used multiple images taken at various specifications along with specialized computer programs in Matlab, and the Astra Toolbox. 

Results: The images taken allowed scientists to identify a short third pair of legs and lateral spinnerets unique to the Hersiliidae family of spiders, that differs from the extinct and extant families. The specimen can be seen in Figure 1.  This is why scientists proposed the Hungarosilia genus to accommodate the new arachnid fossil. Based on drill cores samples, the climate for the Ajka Coal Formation has been projected as tropical, with large amounts of rain. The forests were likely fern dominated in the subtropical or tropical environment.

A dark mass with multiple protruding stick like objects (the spider body and limbs), as well as two pointy objects coming from the rear of said dark mass. The pointy objects are the spinnerets, it appears. Entire body is about 3 mm in height; with legs, about 6 mm in width.
An image of the spider scanned from the amber inclusion, that was found in the Ajka Coal Formation in Europe. Hails from the Mesozoic time period. Scale bar = 2 mm

Why is this study important? This specimen is unique in that it is a new genus of spider from the Mesozoic. The only other genera in this spider family that have been described so far are Burmesiola and Spinasilia, both of which were found in amber from Myanmar. These two genera have distinct differences that set them apart from the newly found specimen, which differs mainly with the longer rear end, triangular separation between the spinnerets, and short middle section. 

Broader implications beyond this paper: Up until this specimen was found, there have been very few spiders or spider-related inclusions found in the Ajka Coal Formation . With the identification of this specimen, the Hersiliidae family of spider establishes the oldest known record for this family in Europe, as well as being the second record of this fossil from the Mesozoic. The discovery of this specimen has greatly improved the knowledge on the Mesozoic diversity of the family Hersiliidae, and the Ajka Coal formations paleoenvironment. Further specimens may help to expand the diversity of spiders in the Mesozoic of Europe.

Citation: Szabo, Marton, Jörg U. Hammel, Danilo Harms, Ulrich Kotthoff, Emese Bodor, Janos Novak, Kristof Kovacs, and Attila Ősi. “First record of the spider family Hersiliidae (Araneae) from the Mesozoic of Europe (Bakony Mts, Hungary).” Cretaceous Research 131 (2022): 105097.

Determining the Maturity of Bivalves in Puerto Rico and the Dominican Republic to Determine Historical Processes that Affected Deposition

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Strontium Isotope Stratigraphy for Oligocene-Miocene Carbonate Systems in Puerto Rico and the Dominican Republic: Implications for Caribbean Processes Affecting Depositional History

Ortega-Ariza, D., Franseen, E. K., Santos-Mercado, H., Ramírez-Martínez, W. R., and Core-Suárez, E. E.

Summarized by Andrea Gann, a graduate student pursuing a master’s degree in Environmental Science and Policy at The University of South Florida. Currently, she is in her second year. After graduation, she plans to work as an environmental science analyst for an environmental consulting firm in Tampa. When she’s not studying environmental science, she enjoys kayaking and swimming in the many springs located in Florida. 

What was the hypothesis being tested? This paper aims to establish the ages of two fossil clam species, Kuphus incrassatus and Ostrea haitensis, by using absolute dating methods. Absolute dating is when scientists calculate the amount of radioactive decay in the isotopes of minerals found inside the fossil. Isotopes are known as elements that share the same number of protons while differing in their number of neutrons. This data was used to better understand under what conditions certain shallow marine systems in Puerto Rico and the Dominican Republic were deposited. 

What data were used? The data collected in this study is called strontium (Sr) isotope data. Strontium is known as a common trace element, which is a chemical component present in many organisms that includes both essential and non-essential elements. For example, zinc is considered an essential element in most organisms, while other elements like aluminum or uranium are deemed non-essential. To study and determine the ages of certain fossils – in this case, bivalves – the authors are applying the 87Sr/86Sr ratio. Within strontium are four isotopes, and these two are the closest to each other in abundance. The ratio involves the decay of rubidium isotope 87Rb, a trace element, into  87Sr over geologic time. By studying the increase of 87Sr/86Sr, researchers can determine the absolute age and origin of certain fossils by calculating ratios.  

Methods: The researchers began by collecting shell samples of both Kuphus incrassatus and Ostrea haitensis bivalves and drilling small amounts of their shell to chemically analyze. These shells are composed of low-magnesium calcite, which means that they tend to be fairly stable where other forms of minerals would change in the fossilization process.  Scientists compared the ratio of the bivalve fossils to modern-day fossils to ensure no chemical changes would have affected the 87Sr/86Sr ratio. Here, a Thermo- Finnigan MAT 253 isotope ratio mass spectrometer was used to calculate the isotopic ratios of the bivalves, which were then juxtaposed with the ratios of modern mollusks. Concentration levels of other trace elements such as iron and manganese were also confirmed and compared with Sr values as another indicator of chemical alteration. Finally, the Sr isotope ratio produced three values – each with a corresponding minimum and maximum age. The 87Sr/86Sr ratio value reflects the mean age, while the minimum and maximum values exist as a range for any error or uncertainty.  

Results: 117 samples were collected, and 41 of those samples were at values expected of a shallow-water environment. . The authors also discovered a depletion in carbon values that could have been caused by freshwater runoff or an insufficiency of open-ocean water interchange. The absolute age of the bivalves, used to determine the ages of the rocks in which they were found, were included in the results. For example, the San Sebastian Formation in Northern Puerto Rico was set in the middle-late Oligocene at a mean age range of 29.78 to 26.51 Ma. Another formation named the Yanigua-Los Haitises Formations were set in the Middle Miocene at a mean age range of 15.75 to 15.25 Ma.

A four panel figure labeled A to D. A- shelly layer of fossils with a sharpie for scale. B- shelly layer of fossils with a pointer finger indicating to a zigzag break in the structure. C-horizontally striped microstructures that appear similar to a ripple effect. D. layered fossilized tissue with round edges and smooth overlapping structure that resembles a palmetto leaf.
The images above display the samples of Kuphus incrassatus and Ostrea haitensis bivalves tested in the study. Images (A) and (C) are Kuphus incrassatus which show that the interior shell texture is still intact, as well as the outer layers which have recrystallized. Images (B) and (D) display Ostrea haitensis bivalves with consecutive layers of preserved tissue and partially recrystallized shell texture. The condition of these bivalves demonstrates the lack of chemical alteration found in the study.

Why is this study important? The framework created in this study provides insight into how the chronostratigraphy of bivalves is directly correlated with time and surrounding local processes and regional processes. The meaning behind chrono is time, while the meaning behind strat is ‘layer’. Thus, chronostratigraphy is the analysis of rock layers over time. By identifying the absolute age of these shells, the authors can then determine what global and local processes influenced its deposition. 

Broader Implications beyond this study: This model will allow other stratigraphers and geologists to replicate this study with bivalves or other shells in their own regions globally. The authors describe methods using multiple pieces of scientific equipment (e.g., a Thermo- Finnigan MAT 253 isotope ratio mass spectrometer, microscope-mounted dental drill, transmitted light microscope petrography, plasma atomic emission spectroscope, and more). There is in-depth detail about the formulas utilized to calculate for chemical alteration that can help guide other geologists with their own chronostratigraphy and absolute dating analyses. Overall, absolute dating helps construct a structured timeline and establishes the depositional conditions and processes that were occurring. 

Citation: Ortega-Ariza, D., Franseen, E. K., Santos-Mercado, H., Ramírez-Martínez, W. R., & Core-Suárez, E. E. (2015). Strontium Isotope Stratigraphy for Oligocene-Miocene Carbonate Systems in Puerto Rico and the Dominican Republic: Implications for Caribbean Processes Affecting Depositional History. The Journal of Geology, 123, 539–560. https://doi.org/10.1086/683335

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Diversification Patterns of Trilobites during the Ordovician

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Post-Ordovician Trilobite Diversity and Evolutionary Faunas

Bault, V., Balseiro, D., Monnet, C., and Crônier, C.

Summarized by Alexa Milcetic, a senior at the University of South Florida studying geology, with minors in astronomy and geographic information systems (GIS). She plans on furthering her education by obtaining a master’s degree in planetary geology. After she earns her degree, she plans to work for the National Aeronautics and Space Administration (NASA). When she isn’t studying geology, she loves to listen to music, watch movies, and read.

What was the hypothesis being tested? The hypothesis being tested required an investigation of the evolutionary history of trilobites, marine fossils, after the Late Ordovician Mass Extinction (LOME). Scientists wanted to evaluate the amount of diversity of trilobites after the LOME and understand the shifts in the broad groupings of diversity, called ‘evolutionary faunas’. Researchers asked what kind of environment did these different groups of trilobites live in? How did their differing regions they were acclimated to help or harm them during extinction events that happened after the LOME. 

What data were used? Trilobite data was downloaded from the Paleobiology Database which spanned 23 families. Where they were found, specifically the rock they were found in (lithology), can be used to estimate where they lived and where in the ocean they were found. For this, the Paleobiology Database was primarily used. This database was used to determine the post-Ordovician biodiversity of trilobites. Essentially, researchers put the data into the database, and these scientists then downloaded the information. This was then represented through the creation of a plotted graph (Figure 1), showing the diversity of trilobites throughout this range in geologic time. Using this same database, habitat conditions and the location of where these organisms lived was also collected. The lithology (the geology of their habitat) data became separated into the categories of carbonate, siliciclastic, or mixed. The preference for sediment that these trilobites had changed throughout time, and scientists wanted to see if there was any correlation with this preference and how certain groups became extinct. Bathymetrical data also became separated into categories of shallower or deeper, showing if a certain group preferred living in a certain region of the water where another group would not be able to survive. The latitude locations of their habitats also became separated into categories of low latitude, middle latitude (equatorial), and high latitude.

Methods: These trilobites within this period of the Post-Ordovician were in four distinct groups according to their similar characteristics, environments, and time they lived in. These were then used as variables to evaluate the evolutionary faunas. What the fauna was made of was determined by the latitude, lithology, and overall environment of the habitat they lived in. They looked at who was present, and the features of their environments, to better understand if things like lithology, etc. might explain more of their survival. They took all the data and ran tests to determine if there were patterns driving the biodiversity in these trilobites and tested the results to see if they were statistically significant. 

Results: Four groupings of trilobites showed up in four different chunks of time from the Silurian until the Permian–Triassic extinction (444 to 252 million years ago), where trilobites ultimately went extinct. Throughout the Silurian period, trilobites were highly diverse (i.e., many genera were present; more genera means more diversity). These are called the Silurian fauna. During this same period, these trilobites still maintained a high diversity even at higher latitudes and in richer siliciclastic (i.e., more sand and mud instead of limestone) environments, especially when compared to the more recent faunas. Next, there is the Devonian fauna, where especially in the Early Devonian there was the highest post-Ordovician diversity found within this study. In the Middle Devonian, there was a large reduction in trilobite diversity. This was likely due to the decrease in the amount of atmospheric oxygen, as well as with changes in sea level. The evolutionary fauna that developed here, within the Devonian, occurred during environmental changes, like an increased greenhouse environment, more carbonate environments, and high sea levels, indicating  a warmer climate. In the Late Devonian, diversity within trilobites was still low and the fauna is called the Kellerwasser Fauna.This was still due to the abrupt environmental changes that occurred during the Middle Devonian, that decimated previous evolutionary faunas. After this, there was the Hangenberg Event, known as the end-Devonian Extinction, which affected all existing trilobite groups. The survivors of this are called the Late Paleozoic Fauna (Figure 2). Since there was a decrease in diversity during the Mississippian (Early Carboniferous), there were only a select few faunas able to survive until the Permo-Triassic extinction. 

Figure showing 11 different types of trilobite groups that lived and or died during the time of the Cambrian (521 million years ago) to the end of the Permian (252 million years ago). The great diversity when many of these groups lived, ended as the Devonian ended (360 million years ago). Since this study focuses on Post-Ordovician, the diversity during this time interval was greatest in the Early Devonian. Overall, the diversity of trilobites was greatest in the Ordovician.
Figure 1: Evolutionary history of the different types of trilobites, from the Cambrian where they are first found in the geologic record, to the Permian-Triassic extinction where all trilobites became extinct. The Y-Axis is time in a Logarithmic scale.

Why is this study important? In the trilobites, the diversity ranged vastly across different geologic times, which allowed them to make it through multiple extinction events. With this, we can begin to study who survived and who didn’t, and the common characteristics they shared or did not share with each other, such as: what made them more likely to live, and what characteristics made it more likely for them to die. This study is important because trilobites were an extremely common part of the early Paleozoic and why they went extinct in the pattern that they did (across multiple mass extinctions) isn’t well understood. The variables that likely controlled this include climate change and the environment each of these distinct trilobite groups lived in. While they never recovered from the Late Ordovician mass extinction, there were slight increases in diversity in the Early Devonian, possibly caused by warmer climates and large inland seas. 

Broader Implications beyond this study: These trilobites left us a blueprint. Since something with so much diversity has died out, it is important to find out what could have caused this. Their extinction was heavily affected by high greenhouse gasses. It is important to use this information in the past to decide how to best mitigate and protect the organisms we have today, as human activity is releasing high greenhouse gasses today. Understanding how trilobites responded to these mass extinctions can help us understand how other animals did too. We can use this information to see how current and future trends in climate will affect organisms today.  

Citation: Bault, V., Balseiro, D., Monnet, C., & Crônier, C. (2022). Post-Ordovician trilobite diversity and evolutionary faunas. Earth-Science Reviews, 230. https://doi.org/10.1016/j.earscirev.2022.104035

Small tracks found in Southern Colorado, USA show scientists details about the fossil record in an area that experienced volcanism

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Small bird and mammal tracks from a mid-Cenozoic volcanic province in Southern Colorado: implications for paleobiology

Lockley, M. G., Goodell, Z., Evaskovich, J., Krall, A., Schumacher, B. A., and Romilio, A.

Summarized by Brysen Pierce, a geology major, working on Geographic Information Systems and Technology, as well as environmental science and policy minors. Currently, he is a senior who has not decided what to do for his career path. When he is not studying geology, he enjoys watching movies and hiking. 

What was the hypothesis being tested? Several fossilized animal tracks have been discovered in Rio Grande National Park (Colorado, USA). After locating samples containing tracks near the first site, the authors hypothesized that since there was already one set of tracks located, there could be others nearby in a similar geologic setting. The purpose of this study was to define the tracks and identify what kind of creatures may have made them.

What data were used? Samples were collected from the field and analyzed. The source of the data was in southwestern Colorado in the San Juan Volcanic Field and from a smaller site in New Mexico. At the first site, there were two tracks that indicated two different birds and another unfinished track, which contained small prints that did not follow a distinct trail or were not able to be identified. The second site had four completed tracks that were left by birds and mammal traces that formed another track and there were some more traces that did not complete tracks. 

Methods: The tracks were found close to fifty meters apart from each other in two different locations. The tracks were preserved in a piece of a volcanic block, which had since been moved from its original position; once the rock had been moved, it became exposed. A volcanic block is a piece of a solidified fragment that has been ejected thrown from a volcano by an eruption and is measured to be larger than sixty-four millimeters in diameter. Since these trace fossils were the first of their kind that have been recorded in this type of volcanic environment, researchers wanted to expand on this topic. From here, the scientists were able to collect samples and take casts so that they could do measurements of the prints and better analyze the trace fossils and define what they could have been from. 

Results: Three total samples were collected or casted and brought to museums to study. Three species were identified in this study: two of them were bird species and the last was a species of mammal related to modern day rodents. The birds were some of the smallest found in the fossil record and have relations to creatures like the sandpiper whose habitat is shorelines. Some tracks were not easily identifiable because they are incomplete. The bird tracks in this area were identified Avipeda circumontis named after the region it was found in and the mammal tracks are Musvesigium minutus whose name means small mouse footprints. Both species share similarities between other closely related species that are found in the western United States, which makes identification of the species difficult.

This image shows three smaller images labeled a, b, and c. a) is a picture of the broken off block that is showing the tracks with a measuring tape across the broken surface that measures across at about 23 inches. b) is a drawn model of the block that includes two complete fossil tracks and other markings around the surface that measures 23 inches and shows a 30 cm scale next to it. This image is reversed from a) and shows the clear impressions compared to the photograph. This bird is tridactyl and we can see 8 steps in a row and another set of a couple steps following a separate path in a similar direction of northeast. c) is a 3d modeled created from images of the surface that shows the fossil tracks and two small measuring tools to show the scale of the sample measuring 23 inches and scale of 25 centimeters.
These images show the first site where the bird tracks can be located. a) is the image of the bird tracks in the block which it was found inside of. b) shows a drawn replication of the bird tracks but flipped it. c) a 3d model of the bird tracks on the block in situ. This is telling us that fossil tracks are visibly seen on this site and shows in varying amounts of detail.

Why is this study important? This study is important because it shows us that trace fossils can be found in a volcanic setting, which has previously been unreported. The study shows us what kind of species lived in this area during the mid-Cenozoic and could provide additional information about an environment that has not been preserved in the past with fossils. New types of trace fossils were identified in a setting that previously had produced no fossils. We learned that not only small birds, but also small mammals, once lived in the volcanic province of south Colorado. 

Broader Implications beyond this study: Since this is the first study that has described animal tracks found preserved in volcaniclastic setting, this could lead to other discoveries within similar environments in the geologic record . There is a lot to learn from sites like this because the species that the footprints were left by were previously undiscovered. The bird and mammal fossil tracks found here could be unique to this setting, but this means that tracks are able to be preserved in this type of environment and that the animals were, in fact, leaving evidence behind.

Citation: Lockley, M. G., Goodell, Z., Evaskovich, J., Krall, A., Schumacher, B. A., & Romilio, A. (2022). Small bird and mammal tracks from a mid-Cenozoic volcanic province in Southern Colorado: implications for palaeobiology. Historical Biology, 34, 130-140.

Fossilized Lynx skulls from Southern Italy provide a window into the Evolutionary History of the Endangered Lynx pardinus

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The tale of a short-tailed cat: New outstanding late Pleistocene fossils of Lynx pardinus from southern Italy

Mecozzi, B., Sardella, R., Boscaini, A., Cherin, M., Costeur, L., Madurell-Malapeira, J., Pavia, M., Profico, A., & Iurino, D. A.

Summarized by Vincent Levin, a geology major at the University of South Florida in his third year. He loves geochemistry and is contemplating graduate school. While he isn’t splitting rocks with a tile saw, Vincent loves to spend time at the USF Catholic Student Union, where he is a very active member and part of their leadership team. He also enjoys video games and playing the bass guitar. 

What data were used? This study was conducted on the fossilized remains of a group of large cats, the lynxes, and particularly the Iberian lynxes (Lynx pardinus) (L. pardinus). These fossils were found at the site of Ingarano in Foggia, South Italy. Unearthed there were 415 late Pleistocene Lynx remains. Of these remains, this study focuses exclusively on craniodental fossils, or fossils of the skull and teeth. 

Methods: The fossils were gathered throughout the 1990s by different researchers. To collect the data used in the study, they used CT scans and CT imaging software on the complete skull fossils. This allowed them to create 3D models of the two skulls. They also used ZBrush 4R6, a modeling software, to restore missing points of the skull. They also incorporated other Lynx fossil data from different sites in France, Spain, and other parts of Italy. Lastly, they estimated Lynx body mass using a method that uses skull measurements to determine overall body mass.

This is a map of Europe and part of the middle east. The fossils of Lynx issiodorensis, Lynx pardinus, Lynx lynx, Lynx sp., and the Lynx remains from the Ingarano site are listed here. Lynx pardinus fossils have been found ranging from the middle to late Pleistocene, moving from France and Italy into Spain. The Lynx remains from the Ingarano site are represented by a pink circle in Southern Italy.
The geographic distribution of Pliocene and Pleistocene lynx fossils in Europe. This figure covers a large portion of Europe and shows the distribution of the different species of lynx. In pink is the Ingarano site in southern Italy. The Iberian Lynx, in green, is shown to arise in the early Pleistocene and spread into the Iberian peninsula and into modern day France and Italy.

Results: Researchers determined that all of the cranial remains contained permanent teeth, indicating that they were all from adult cats. Many of the skull pieces and whole skulls still retained many upper teeth, which were beneficial in the final analysis. The lower teeth and mandibles (jawbones) also showed that all the remains were from adult specimens. However, these fossils showed much more size variation, and none of the lower incisors were preserved.

All the characteristics of the fossils found fit the overall morphology of L. pardinus. Overall, the Ingarano samples have larger cranial dimensions than other data sets. They concluded that there was also little sexual dimorphism, with the male to female body mass ratio being mostly equal. Sexual dimorphism is what accounts for biological differences between the sexes of a species.. Due to the limited sample size, it is hard to determine a correlation between Lynx body size and any potential environmental factors.

The most important result of this study was found in the cranium (skull) fossils. The cranium fossils provided a new insight into the evolutionary history of Lynx issiodorensis (L. issiodorensis) as a possible ancestor to Lynx pardinus and the still-living Eurasian lynx (Lynx lynx). L. issiodorensis, hypothesized to be representative of an ancestor of the modern Lynx, was shown to have similar cranial features to L. pardinus. The data found in this study supported the hypothesis that these cranial features were homologous, or features inherited from an ancestor. 

Why is this study important? This study compiled data on 68 craniodental (skull and teeth) Lynx fossils. Teeth and skulls are an important window into the morphology, what it looked like, and ecology, how it lived and interacted with its environment. Many of the studies done on Lynx fossils have lacked any substantial cranium (skull) data. This study was able to add that to the overall discussion on Lynx evolutionary history. Lynx evolutionary history was hard to nail down due to the coexistence of the two modern species of Lynx, Lynx pardinus and Lynx lynx, during the same time period. The addition of the cranium data added some clarity to the overall discussion.

The big picture: The Iberian Lynx (L. pardinus) is currently endangered. This study adds to a decades-long effort to better understand the ecological and biological characteristics of these cats. This could add data to create better conservation efforts for the preservation of this species against natural and manmade threats. 

Citation: Mecozzi, B., Sardella, R., Boscaini, A., Cherin, M., Costeur, L., Madurell-Malapeira, J., Pavia, M., Profico, A., & Iurino, D. A. (2021). The tale of a short-tailed cat: New outstanding Late Pleistocene fossils of Lynx pardinus from southern Italy. Quaternary Science Reviews, 262, 106840. https://doi.org/10.1016/J.QUASCIREV.2021.106840

A Tooth for a Tooth: Evolutionary Development of Dental Structure Based on Common Mutations of the Bearded Dragon

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The developmental origins of heterodonty and acrodonty as revealed by reptile dentitions
by: Salomies, L., Eymann, J., Ollonen, J., Khan, I., & Di-Poï, N.

Summarized by Kat Cool, a fourth-year geology student studying at the University of South Florida. She is pursuing her major with a geophysics emphasis and a minor in Geographic Information Systems and Technology. She is also the proud owner of three bearded dragons that have inspired her interest in this article. In the future she hopes to study meteorology at the graduate level and hopefully specialize in severe weather forecasting.

What data were used?  Discovering evolutionary mechanisms for dental changes could have implications in phylogenetics, taxonomy, and ecological identification of animals that are extinct as well as those still here today. This could be especially useful in key taxa groups that have a poor fossil record or a more mysterious evolutionary history. One group of reptiles the lepidosaurs (snakes and lizards), are a perfect candidate for this research due to their diversity in dental structures. Mutations in the genetic codes of lepidosaurs could provide key insight to the mechanisms behind their dental evolution. One mutation commonly seen is variation of the ectodysplasin (EDA) pathway. This mutation can be observed in many vertebrate species, including humans, and causes changes in the appearance of hairs, feathers, scales, nails, and teeth. The subject for this study group will be the humble bearded dragon (Pogona vitticeps), due to the different stages of EDA mutations one can easily observe. Since this mutation is also known to influence tooth development, scientists decided to look at the dental structure of these morphs as well.

Methods: To analyze the tooth development of bearded dragons, scans were taken to take a closer look at the EDA mutation both during embryonic development and after the hatchlings have emerged from the egg. Then 3D-rendered bearded dragon skulls were compared at 14 days after hatching. The teeth of the wild-type bearded dragon, the leather-back (Sca/+), and the silk-back (Sca/Sca) were then compared based on the appearance (or lack thereof) of pleurodont and acrodont teeth (Figure 1 for images and descriptions of teeth; Figure 2 for images of the lizards).

Figure 1 (A) shows diagrams of different tooth structures. The jawbone, dental pulp, dentine, and enamel are color coded in each of five tooth structures. Bearded Dragons have two of these types of teeth. The first is pleurodont teeth which are shown in the diagram by having one side of the tooth connected to the jawbone while the other side is exposed. The second type of teeth in this diagram of interest to us are the acrodont teeth. The acrodont teeth are shown in the diagram by having the jawbone go about halfway up on both sides of the tooth.(B) A phylogenetic tree showing families and subfamilies of Acrodonta connected by lines based on their relationship. The tree stems off into two main groups: The Agamidae and the Chamaeleonidae. The Lepidosauria reptiles are on the Agamidae side of the tree. (C) 3D-rendered skulls of lizards representing the main Acrodonta subfamilies. Each skull shows an X ray of the bones and teeth in the lizard’s skull from a straight on angle as well as from the side of a lizard’s skull. The anterior pleurodont teeth are highlighted in red and the acrodont teeth are noncolored
Figure 1 (A) Different tooth attachment types in vertebrates. There are two main types of teeth present in these reptiles: Pleurodont teeth are set on the inside jaws, while acrodont teeth are generally larger and attach to the jaw by connective tissue. Pleurodont teeth are accepted as the norm for Lepidosauria; however, there are certain families like Agamidae, Chamaeleonidae, and Trogoniphidae that show an understudied mix of pleurodont and acrodont teeth or a singular acrodont tooth. Another unique feature of living lepidosaurs is the lack of or absence of tooth replacement in acrodont teeth. (B) Phylogenetic tree showing families and subfamilies of Acrodonta. The Lepidosauria clade includes the Rhynchocephalia order with the single surviving species, the Tuatara, as well as the Squamata order with many living members like lizards and snakes (C to J) 3D-rendered skulls of lizards representing the main Acrodonta subfamilies

 

Results:  It was found that wild-type hatchlings had eight acrodont teeth and one small pleurodont tooth per jaw. There is also a central egg tooth on the middle jaw bone (premaxilla) that is replaced with a pleurodont tooth soon after hatching. However, it was found that both scaleless bearded dragons (Sca/+ and Sca/Sca) often did not have pleurodont teeth on their premaxillary bone, leading to about half of juvenile dragons with an EDA mutation having few or no teeth on this bone at all. It was also found that bearded dragons with EDA mutations had fewer teeth in total than the wild-type dragons, as well as wider teeth. These observations were more evident in the silk-back juveniles (Sca/Sca).

Figure 2 Two female bearded dragons sitting next to each other on a pillow. They are laying on their stomach with their heads looking forward. Their round abdomen consolidates by their hind legs where their long tails extend out of frame. The bearded dragon on the left is a wild type bearded dragon. She is yellow and brown in color and her spikes are much more apparent than the bearded dragon on the right. The bearded dragon on the right is more orange and tan and lacks the same spiky texture as the other bearded dragon.
Figure 2. An image of a wild-type bearded dragon (left) and a leather-back bearded dragon or Sca/+ (right). If you are familiar with bearded dragon morphology, the EDA mutation is responsible for two of the most well-known morphs: the ‘leather-back’ and the ‘silk-back’. The leather-back bearded dragon (Sca/+) has one copy of the EDA mutation, resulting in reduced scale size than the bearded dragon’s without this mutation (also called wild type in this study). This reduction in scales creates a leathery appearance, earning these little mutants the colloquial name ‘leather-back’. The silk-back (Sca/Sca) bearded dragon has two copies of the EDA mutation: one from each parent. The result is a more extreme version of the features observed in the leather-back dragons: instead of reduced scales there appears to be an absence of scales all together.

Why is this study important: At the time of these results, the scaleless bearded dragon was the first known example that researchers had found of a gene mutation that resulted in position changes in teeth. These results provide a contrasting prospective to results found when studying the dental structures of mice. While the research with mice indicated that vertebrate tooth position was based on a complex model of gene expression patterns, the scaleless bearded dragon data suggests tooth identity can be produced with the modification of a simple gene.

The big picture: The simple modifications of the EDA gene had very observable effects on the position of the teeth. Though more research is necessary, this study shows that through observations of living species today, mechanisms of dentition diversity can be discovered through many different approaches to better understand evolutionary development. Though it is sometimes a long, slow process that can span across millions of years, it can also sometimes be isolated to a change in a single gene at a specific moment. 

Citation: Salomies, L., Eymann, J., Ollonen, J., Khan, I., Di-Poï, N. (2021) The developmental origins of heterodonty and acrodonty as revealed by reptile dentitions. Science Advances 7(51). DOI: 10.1126/sciadv.abj7912

Examining the types of Devonian trilobites in North Africa

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Trilobite biodiversity trends in the Devonian of North Africa

Bault, V., Crônier, C., Allaire, N., & Monnet, C.

Summarized by Tom Shea, a fourth-year geology major at the University of South Florida. After completing his degree, he plans on going to graduate school to study seismology. Outside of class, Tom likes to go to USF games and spend time at the beach. 

What data were used?  1,171 trilobite fossils of 556 different species found in 168 locations throughout Northern Africa.

Methods:  This study ranked the trilobite samples by taxonomic rank (i.e., species, genus, family, etc.) to find ranks which were unique to Northern Africa and then used that information, called taxonomic richness, to show the biodiversity trends over the course of the early Paleozoic. This experiment focused heavily on trilobite genera (plural of genus).

Results: The data show that the biodiversity of trilobites varied significantly from the late Silurian Period through the Devonian Period. During the late Silurian, specifically during the Ludfordian and Přídolí Epochs (~427-423 MA and ~423-419 MA, respectively), biodiversity of trilobites declined steeply until there were eventually zero trilobites in the entire region (figure 1; also refer to figure 1 for the geologic time scale terminology used throughout this summary). The biodiversity of trilobites started rising again once the Devonian Period began.

Figure: A graph showing the biodiversity of trilobite genera in the late Silurian Period and the entire Devonian Period. The x-axis represents time, running from the Ludfordian Epoch to the end of the Devonian Period. The y-axis represents the number of genera, running from 0 to 60. Four lines are plotted on the graph: one for shareholder quorum sampling for 70 samples, one for sampled in bin index, one for range-through diversity, and one for boundary-crosser diversity. Each of the four plots show that the population of trilobites in this area started at nearly none at the end of the Silurian, but then exploded during the first few epochs of the Devonian before crashing back down near zero once again in the mid to late Devonian.
Figure 1: This graph shows that the number of different trilobite genera peaked in the Emsian Epoch of the Devonian Period after a few million years of rapid growth, followed by the population crashing right back down to near zero. The different curves indicate different measures of diversity, but all follow the same overall trends of the highs and lows of diversity.

During the early to mid-Devonian, and particularly in the mid to late Pragian Epoch within the mid-Devonian (~410-407 MA), trilobite diversity rose rapidly, from around 10 different genera in an interval to around 40 in only 1.5 million years. Once the Pragian gave way to the Emsian Epoch (~407-393 MA) though, the trilobite numbers in North Africa began sharply decreasing once again. This decrease continued until around halfway through the epoch, when the trilobite biodiversity suddenly and rapidly rose once again. The trilobites in North Africa eventually peaked with roughly 60 different genera sampled in a single interval near the end of the Emsian. After the peak, the number of genera began rapidly falling, a fall which became even steeper when the Emsian became the Eifelian Epoch. The event became known as the Choteč Event, which was relatively minor to most creatures for an extinction event but was absolutely devastating to trilobites in North Africa; this was caused by water becoming much deeper and causing extinction in shallower water trilobites. Trilobite numbers continued falling until there was not a single genus of trilobite living in this part of North Africa, which happened shortly after the Frasnian Epoch of the Devonian (~383-372 MA) began. Some genera of trilobites would return to North Africa later in the Frasnian, and these trilobites in the area fared better than many other creatures would in the Kellwasser mass extinction (~372 MA, the boundary of the Frasnian and Fammenian epochs of the late Devonian), which was one of the largest mass extinction events in history. Three of the five remaining orders of trilobites went extinct due to the Kellwasser event, severely limiting the chance of trilobite biodiversity in North Africa being anywhere near what existed prior to the Choteč Event.

Why is this study important? This study is important because it revealed a lot about the history of the past ocean, now part of Morocco, and the chronostratigraphy of that area, meaning the types of rocks in relation to the time period. This study ties sea level change and hypoxia (i.e., low levels of oxygen) to biodiversity in trilobites. For example, the sea level rise of the Choteč Event caused extinctions in shallow water trilobites; since trilobites were unusually hard-hit during the Choteč, this allowed scientists to see a different view of this geologic event. The Kellwasser extinction showed increasing hypoxia that led to extinction as well. With such a great fossil record like the trilobites seen here, we can get extremely detailed pictures of how certain groups responded to extinction events.

The big picture:  This study shows that by looking at the fossil record, you can tell a lot about the geologic history of an area. It is also important to note that this study helps us understand more about extinction events and biodiversity trends in the Paleozoic of Africa, as most paleontological studies have focused on data collection from Europe and North America that tend to bias our understanding of global events. 

Citation: Bault, V., Crônier, C., Allaire, N., & Monnet, C. (2021). Trilobite biodiversity trends in the Devonian of North Africa. Palaeogeography, Palaeoclimatology, Palaeoecology, 565, 110208–. https://doi.org/10.1016/j.palaeo.2020.110208

From Lichen Trees to Woody Trees

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Ordovician-Devonian lichen canopies before evolution of woody trees

Gregory J. Retallack

Summarized by Saraiyh Newton, an undergraduate geology student at University of South Florida.

What data were used? Nematophyte fossil data was collected from the Silurian-age Bloomsburg and Ordovician-age Juniata formation (in Pennsylvania and Tennessee, USA respectively); ancient layers of soil called paleosols, that encases the fossil nematophytes, were also used in this study. Nematophytes are a loosely defined grouping of organisms such as algae and lichen found in the Silurian to the Devonian period that were able to form large canopy- like structures (similar to tall trees in modern forests); in this study, the nematophytes are the lichen canopies the title alludes to. The researcher used various data from modern plants to calculate estimated heights of the fossil lichen canopies. 

Methods: This study illustrates the presence of these nematophytes that created canopies, which has components that could have nurtured early land plants that grew under it, which would eventually allow woody trees to thrive. First, the study identifies where the nematophytes are through various methods, like visual surveys of the paleosols for features such as extensive fungi-like root traces.

Brownish bedrock with white, clay cracks lines covering the bedrock (these lines are root traces) on this bedrock is a rock hammer on the right of the picture for scaling and multiple arrows along the top of the image to indicate where the root traces are purposes. Total image is about 2 hammers high.
Evidence of nematophyte root structures (white arrows) in paleosols of the late Silurian Bloomsburg Formation. Hammer for scale.

After finding the nematophyte remnants, the study author calculated the possible height that the nematophytes might have grown to when they were alive. Plant height is calculated by using an allometric growth equation, which is the relative change in proportion of a part compared to its body, based on 670 modern species of trees. This equation uses the trunk’s diameter at about 1.4 meters above the trunk’s base, or breast height, to calculate the height of the tree. With the calculated height, Retallack calculated the possible density of plants per square meter to create a picture of what forests may have look like with these nematophytes. 

Results: The calculated density and spacing between the trees (which is also found within the paleosols) illustrates a dense cluster of the nematophytes within ancient forests. Since these nematophytes were most likely densely clustered all over forest during the time, these organisms might have nurtured and created an environment where vascular plants, like woody trees, would be able to thrive in the future (later Devonian to present, when trees became extremely widespread). This could have happened because the nematophyte fungi-like roots had an extensive reach in the soil and this fungi network could have nourished environments to the point where plants would have thrived.

Why is this study important? This topic is quite interesting because when we look at modern lichen, they are mostly flat, low growing organisms. They usually do not grow very tall, but they can spread over different surfaces in the forest. So, knowing this about modern lichen species and learning that there was once lichen species that were big enough to have canopies could show how forest ecosystem and species changes over time. 

The big picture: These nematophytes can illustrate how a dominating species in a region can create an environment that allows newer species to thrive in the future. These nematophytes made a good environment for woody trees to thrive in and woody trees eventually became a dominate plant grouping, so we may be able to study how woody trees might be facilitating the evolution of other organisms, too. Learning about how species affect the world around them can improve our knowledge on how ecosystems can change over time. 

Citation: Retallack, G., 2022. Ordovician-Devonian lichen canopies before evolution of woody trees. Gondwana Research, 106, pp.211-223.

Ancient saber-tooth cats may have been more social than we thought

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Computed tomography reveals hip dysplasia in the extinct Pleistocene saber-tooth cat Smilodon

Mairin Balisi, Abhinav Sharma, Carrie Howard, Christopher Shaw, Robert Klapper, Emily Lindsey

Summarized by Nicole Christensen, a senior geology major at the University of South Florida. She went to community college for her Associates’ degree, and initially started working on a degree in Environmental Engineering before pursuing geology instead. She likes many different fields in geology and isn’t yet sure what she would like to specialize in, but she knows she’d like to get her Master’s degree someday. In her spare time, she likes to play music, draw, and knit.

What data were used? The pelvis (hip) and right femur (upper leg bone) of a saber-tooth cat were found in the Rancho La Brea asphalt seeps in California. The pelvis was an unusual find, as it is asymmetrical, with a build-up of bony growth on the right side. The disfigured right hip socket is shallow and oval-shaped, rather than the circular shape of a healthy socket. This disfigurement was originally thought to be due to an infection when the animal was alive; however, further disfigurement is seen on the later-found matching right femur, which bears a flat head instead of a typical rounded one, to fit the shallow hip socket.

Methods: All fossils were collected from the same deposit to limit the range of time represented in the study. Dr. Balisi and her team then observed the surface of the pelvis and femur, comparing their characteristics to other deformed bones from different specimens of the same species. A 3D scan was taken using an Artex Space Spider, which is a type of 3D scanner that produces high-resolution color scans. They then used CT scans to capture images of the internal structure of the bones and allow the 3D models to be cross-sectioned. The cross-sections allowed them to determine cause of the deformations. Since the bone lacked fractures, calluses, or healing markings and the bones did have the presence of arthritic degeneration, researchers were able to narrow down the causes, explained in the results. In order to estimate body size, they measured the pelvis length and femur circumference in question, as well as other deformed and non-deformed femurs and pelvises of other specimen from the same location as a comparison. 

Four different angles of the deformed pelvis on white background, each to show off the extent of the deformation clearly. The right hip socket where the femur would fit is much shallower and larger than the non-deformed left hip socket. The left hip socket has a ridge to keep the femur in place, which the right hip socket is missing. The pelvis is asymmetrical; the right side is smaller with thick bony growths, while the right side is smooth.
Figure 1: The recovered deformed pelvis of a saber-tooth cat. A) The right-side view, showing deformation of the hip socket. B) The left-side view, showing a non-deformed hip socket, but with extra bone growth around the edge. C) The top view and D) bottom view, showing that the pelvis is asymmetric.

Results: The deformations seen in the femur and pelvis, shown in Figure 1, are consistent with hip dysplasia, a condition that the Smilodon in question was born with, rather than due to an injury later in life. The femur wasn’t fully developed, and so it didn’t properly fit into place against the pelvis. This would have led to pain when walking, causing the cat to not bear weight on its right leg. Researchers ruled out possibilities that the cat could have had an injury, infection, or degeneration over time. If the cause was injury or infection, the femur and pelvis would have been fully developed before the degeneration began, and so the top of the femur would not have been affected. However, the femur of this study has a deformed head, indicating the hip socket was not properly developed. In the same area that the studied pelvis and femur were found, there were several other pelvises that showed signs of deformation similar to the pelvis of this study.

Why is this study important? Saber-tooth cats are ambush predators. They wait until the right moment to leap at their prey and then drag it to the ground. It would have been very difficult for one to reach adulthood without being able to use one of its hind legs effectively. Based on the size of the pelvis and femur, the studied Smilodon lived to adulthood. Hip dysplasia begins to affect animals from a young age. This means it is likely that saber-tooth cats lived in communities, which provided both food and protection from predators to those who could not take care of themselves.

The big picture: Evaluations of bones and their markings can lead to discoveries about the lifestyle and behavior of extinct animals, even ones as well-known as Smilodon. Many living species of cats do not show social behavior, making this an advancement in understanding the behavior of Smilodon. Modern technology, such as CT scans, can bring about new methods of evaluating bones past their surface appearance. In this study, CT scans showed evidence of degenerative arthritis in the right hip socket, as well as markings on the top of the femur. Both of these indicate the deformation results from hip dysplasia. CT scans could also build a paleopathology dataset for reference in future studies. 

Citation: Balisi, M. A., Sharma, A. K., Howard, C. M., Shaw, C. A., Klapper, R., & Lindsey, E. L. (2021). Computed tomography reveals hip dysplasia in the extinct Pleistocene saber-tooth cat Smilodon. Scientific reports, 11(1), 1-12. https://doi.org/10.1038/s41598-021-99853-1

 

Crab Population Decline Since the Late Pleistocene

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Predation Scars Reveal Declines in Crab Populations Since the Pleistocene

Kristina M. Barclay, Lindsey R. Leighton

Summarized by Nicholas Stanton, a geology major at the University of South Florida. Nicholas is a Navy veteran who went back to school to follow his passion in the study of Earth’s history. Nicholas has worked for USGS for 2 years as a hydrographer, continuing his love for all things science.

Data that were used: The number of customers that visited Joe’s Crab Shack in a month was the determining…. JOKING. The data that was used in determining if there was a decline in crab populations is quite fascinating and it starts with snails. The Tegula funebralis to be specific, but to make it a little easier these can be referred to as a black turban snail. These snails are extremely helpful, telling stories of the past by their healing attributes. They leave remarkable healing scars after attacks from predators, also known as predation scars.

Methods that were used: So, we just count how many snails have predation scars and that accounts for how many crabs there are in the ocean right? Well, there are a few other factors that need to be eliminated before we can equate these two pieces of information. For example, can the failure of crab attacks account for fewer scars due to the snail shell never being penetrated to create a scar in the first place? Or, can the size of the snail and the size of the crab determine the amount of predation scars found? Well, it is a good thing science rules and we have a bunch of cool scientists that have already conducted studies to help in answering these questions. Other studies have inadvertently shed light on this by answering these questions, even though the purpose of their study was not to calculate crab populations. This other study ended up showing that a change in the success of crab predation is not an explanation for a change in repair frequency. Instead, it is likely that the change in repairs is caused by the change in crab population. In the study summarized here, fossil and modern specimens were collected to compare and determine the crab abundance dating back from the Pleistocene to present day, with the maximum geologic age for the fossils extending to 120 ka (thousand years). Most of the fossils were taken in southern California, specifically the Palo Verdes Hills and the San Diego area. The modern specimens also came from these same areas as to reduce biases in the study. A total of 712 fossil specimens were gathered, 261 from the Palos Verdes Hills area and 451 from the San Diego area. The modern specimens came from seven locations in the same two areas previously listed. Collecting these modern samples was tedious to ensure certain biases did not enter the study. Researchers would walk up and down in symmetrical lines spaced two meters apart collecting around ten to twenty snails on each line. This was done until a total of 1,152 snails total were collected.

A dark colored snail with a cone shape that gets narrower as it extends upward. There is scar, which is a jagged vertical scar that covers 2/3rds of the cone shaped shell on the side. This scar was caused by predation from a crab. Left is a side view, right is a bottom view of the snail
Figure 1: These are examples of predation scars on the black turban snail. In box A the red arrow is pointing to a typical repair scar seen in these snails. Box B shows the size of the snail being taken at the time of attack. This helps show the size at which the snail was and the success of the attack. A snail with a high conical shape and a large groove covering nearly 2/3 of its body shows signs of repair from predation scars.

Results: It was discovered that modern black turban snails have fewer scars than those fossils dating back to the Pleistocene. It was concluded from the study that changes in the frequency of repairs since the Pleistocene is indicative of a change in the number of attacks. The maximum size of repairs between the fossils collected and modern samples were similar, showing crab strength had not changed much over the years. This helped eliminate the thought that lower predation scars were due to the lower success of attacks. This tells the researchers that the crab population has declined since the Late Pleistocene, due to the decline in predation scars in snails.

Why is this study important? Paleontology is crucial for understanding the story book of Earth’s past. It is a nice guide in determining questions about Earth’s future, as well. Fisheries have poor data and little money to invest in expensive research on how to maintain their fishing numbers in the ever-declining industry. Overfishing is playing a huge part in the decline of not only crab population, but thousands of species of marine life. For example, Somalia was once a successful fishing port, but due to larger countries overfishing those waters, the economy collapsed. This is a devastating notion that an entire country’s economy can be significantly affected due to overfishing.

The big picture: This study has mapped an entire population of crab, and this can inform fisheries on how to sustain a healthy number, without depleting the entire species. Things such as climate change, long line fishing, and pollution are wiping out our marine diversity swiftly. Paleontologists, as well as all other scientists, understand the effects of climate change and pollution on Earth’s ecosystem. These scientists are on the front lines combating these realities with knowledge, with evidence, and with SNAILS! 

Citation: Barclay, K. M. & Leighton, L. R. (2022). Predation scars reveal declines in crab populations since the Pleistocene. Frontiers in Ecology and Evolution. https://www.frontiersin.org/articles/10.3389/fevo.2022.810069/full