New Fossil Evidence Reveals How Killer Whale And Other Hunting Whales’ Feeding Preferences Evolved

The origins of the killer whale ecomorph

Summarized by Lara Novalvos, a senior at the University of South Florida, majoring in Marine Biology and with a double minor in Geology and Environmental Science and Policy. After graduation, she expects to earn a Ph.D. in Oceanography. In her free time, she enjoys traveling, reading, and working out.

What was the hypothesis being tested: Scientists in this study are testing the hypothesis that hunting mammals is a trait that evolved more than once in whales and dolphins. The killer whale (Orcinus orca) and the false killer whale -a species of dolphin that resembles killer whales in feeding habits- (Pseudorca crassidens) are the only cetaceans (the group that contains whales and dolphins) that hunt marine mammals, a trait that was thought to have evolved once.

What data were used?:  A cetacean partial skeleton fossil found on Rhodes, Greece. The fossil skeleton preserved (among other bones) was its mandible (lower jaw), some teeth, and otoliths (“earstones”) belonging to fish that were eaten as the whale’s last meal.

Methods:  Morphological traits of the discovered species Rododelphis stamatiadisi were compared to those of other extinct and extant cetaceans (especially teeth count, size, and shape and upper jaw size) to build and infer an evolutionary tree that shows how the killer whale, the false killer whale, and the newly discovered Rododelphis stamatiadisi are related.

ResultsRododelphis stamatiadisi, the species found on the beach in Greece, is an extinct whale from the Pleistocene (2.59 million years ago – 11,700 years ago) that fed on fish. The results of the evolutionary (phylogenetic) analysis indicates that Rododelphis’ skull morphology is more closely related to that of false killer whales, placing them as sister taxa on the tree. However, another fish-feeding whale fossil previously discovered, Orcinus citoniensis, is considered killer whales’ closest relative. Researchers analyzed the teeth, jaws, and size of many cetaceans, extinct and extant, and concluded that delphinids (small whales with teeth such as dolphins, killer whales, pilot whales, and close relatives) evolved in six different lineages, half of them having many small teeth, and three of them having bigger, fewer teeth. From one of the lineages with few big teeth, killer whales evolved; false killer whales also appeared in a lineage of whales with big few teeth but not from the same one killer whales evolved.. These results indicate that the trait of feeding on other marine mammals appeared twice in the evolutionary history of whales, rather than having a single origin.

The figure above displays different delphinid species and its relationship based on morphological and molecular analysis. The phylogenetic tree shows a group of branches towards the middle of the tree colored in orange; these represent the lineage where the present killer whale evolved and its closest known ancestors. Towards the bottom of the tree, branches containing today’s false killer whale and its known lineage are colored in purple. The most closely related species to Orcinus orca is Orcinus citoniensis, while the most closely related species to Pseudorca crassidens is the recently discovered Rododelphis stamatiadisi; both extinct species fed on fish, whereas both killer whales species feed on other mammals, suggesting that the trait evolved in two separate instances.
The evolutionary tree containing extant killer whale and false killer whale. Orange branches show species in the killer whale’s lineage; purple branches show the false killer whale’s ancestors and lineage. Killer whales belong to a lineage that evolved before the false killer whale’s lineage did. Rododelphis stamatiadisi is more closely related to false killer whales than it is to killer whales; moreover, false killer whales are more closely related to Rododelphis stamatiadisi than to killer whales.

Why is this study important?: This study provided an opportunity to revise the evolutionary groups of the whale group. It focused on how different feeding habits evolved within the group, allowing for a deeper understanding on how the different species adapt to new environments, food abundance, or even climate change. Whaling has caused killer whales to switch to smaller prey, allowing us to observe how these whales adapt their feeding habits to different food abundance.

Broader Implications beyond this study: Research suggests that the coexistence of many large predators lead to the selection for even larger creatures; this study suggests that marine mammal predation can be correlated with whale’s gigantism. Both Orcinus orca and Pseudorca crassidens feed on marine mammals, but their most common ancestors did not.  Although the exact origin of why whales became so large is still unknown, it has been hypothesized that gigantism drove these two killer whales to develop their particular feeding preference.

Citation: Bianucci, Geisler, J. H., Citron, S., & Collareta, A. (2022). The origins of the killer whale ecomorph. Current Biology, 32(8), 1843–1851.e2.  

The diversity of 85-million-year-old European freshwater snails was influenced by global climate change

Onset of Late Cretaceous diversification in Europe’s freshwater gastropod fauna links to global climatic and biotic events

Summarized by Jordan Orton. Jordan Orton is a geology major at the University of South Florida. Currently, he is a senior. He plans to work for the water management district to help protect and preserve the aquifer system to ensure we have plenty of safe water to drink and use. When he’s not studying geology, he loves to watch movies, garden, play board games, and go on little adventures. 

What was the hypothesis being tested? The hypothesis of this paper is to determine which factors influenced the rate of speciation (the rate that new distinct species evolve from a common ancestor) to increase so rapidly. Was it because of annual precipitation, average temperature, geographic distance, or continental area (which is determined by the sea level)?

What data were used? Data for this study was collected previously by the same authors and includes estimates of temperature, precipitation, and other variables by geographic location. Their data set also included taxonomic records of 3,122 species of snails represented in this fossil record.

Methods: They compared the results of a birth-death model (a statistical model of how the population of a species changes over time) and a multivariate birth-death analysis (a more complex statistical model to estimate population changes over time that takes into account several contributing factors) with shifts from a 10-million-year timeframe before the peak in speciation of snails to a 10-million-year timeframe after the peak in speciation of snails in order to determine which of the four variables in the hypothesis most affected the rate of speciation.

Results: The researchers analyzed four factors that may have contributed the most to this increase in diversity of snails: annual precipitation, mean annual temperature, geographic distance, and continental area (which is a function of sea level rise and fall). According to the results of the analyses and models, the factors that had the most influence for so many species of snails evolving was a reduction in continental area (i.e., sea level rise) and an increase in geographic distance. 

A reduction in continental area means that sea levels rose and flooded parts of the continent, creating new niche habitats that are brackish (slightly saline) to freshwater. This allows species that can tolerate the less salty waters have a place to flourish and escape predation from marine organisms. This coincided with the Cretaceous Terrestrial Revolution, a bloom in diversity of flowering plant life, and high global water surface temperatures, which also increased marine animal diversity. The creation of these new habitats allowed multiple species to develop and feed from varying types of new flowering plants that were also diversifying in the new habitats. Over time, these organisms evolved into new species that specialized which plants they consumed (similar to the example of Darwin’s finches). The secondary factor that allowed for this increase in diversity of snails is that there was a greater distance between continents, so there was more habitable area for the snails to spread out into. Because the snails venture out further apart, they don’t have the opportunity to intermingle with each other as much, which causes more species to develop

The rate of extinction of snails was consistent through each of these 10-million-year windows, so the rate of extinction wasn’t particularly affected by these four factors. It is likely that there was a decline in the rate of speciation from 85 Mya to 80 Mya due to interspecies competition. Interspecies competition is when there are too many different species competing for a limited resource, so there is a decline in population.

This figure consists of four bar graphs: speciation rate from 95-85 Mya, speciation rate from 85-75 Mya, extinction rate from 95-85 Mya, and extinction rate from 85-75 Mya. The x axis is a range from -7.5 to 2.5 and the y-axis is the time period for that graph. Each graph has 5 factors that are correlated to rate of speciation or extinction: diversity, annual precipitation, mean annual temperature, geographic distance, and continental area. The factors that correlate most with increasing the rate of diversity from 95-85 Mya are an increase in geographic distance and a decrease in continental area, the factor that correlates most with the decline of the rate of speciation from 85-75 Mya is diversity. The rate of extinction from 95-85 Mya was not correlated to any of the factors, and the rate of extinction from 85-75 Mya was correlated to a decrease in continental area. The other variables: annual precipitation and mean annual temperature had a small effect on the data.
This figure shows the correlation strength of the four variables from the hypothesis plus the effect diversity has on the rate of speciation and extinction in the time period 95-85 Mya and 85-75 Mya. The factors that correlate most with influencing the rate of speciation in the period of 95-85 Mya are a decrease in continental area and an increase in geographic distance, while the factor that correlates most to influencing the rate of speciation in the period of 85-75 Mya was diversity. The rate of extinction was not heavily influenced by any of these variables from 95-85 Mya, but the drop in extinction rate from 85-75 Mya was influenced by a decrease in continental area.

Why is this study important? This study is important because there hasn’t been much research into the factors that drove the diversity of species of European freshwater snails; the marine and terrestrial snails are more studied and better understood.

Broader Implications beyond this study: Sea levels and average annual temperature are rising today. If we want to understand what sort of impact human activity is having on the increasing and decreasing rates of speciation of snails, we need to understand how they were affected by the paleoclimate (historical climate). We need to see how snails reacted to these conditions in the past to have a baseline that we can compare to how they react now to the same conditions (which are now being driven by humans).  Scientists can then determine how human activity (habitat destruction, nutrification, etc.) is affecting their rates of speciation. 

Citation: Neubauer, T. A., & Harzhauser, M. (2022). Onset of late cretaceous diversification in Europe’s freshwater gastropod fauna links to global climatic and biotic events. Scientific Reports, 12, 1–6. 

Meet the Museum: Waloseum in Norden, Germany

Linda here, 

I recently visited the Waloseum, a museum organised by the seal sanctuary Nationalpark-Haus Norddeich in Norden, on the German North Sea coast. While the seal sanctuary has its own exhibition, focussing on everything related to seals, the Waloseum showcases the local fauna with a strong specialisation on cetaceans and shore birds. Even though their name sounds a bit like it, they have no live whales, they show models, skeletons, videos, and audio recordings of whales. But since the Waloseum is part of the local seal sanctuary, the ground floor of the building also hosts the quarantine station for baby seals which were found sick, injured or abandoned on the beach. The visitors can spend some time observing baby seals; though to be honest, while very cute, a sick baby seal is not really doing a lot of interesting activities, so let’s move on, so they can rest and recover. Other live animals exhibited here include an aquarium with local fish that live close to the sea floor such as catsharks or flatfish, and benthic invertebrates like echinoderms, allowing visitors for example to closely observe the complicated anatomy of sea star locomotion in action (fig 1). Also included in this area is a wonderful collection of mollusc shells such as cone snails, fearsome predators. 

Figure 1

The lower floor of the Museum hosts the whale exhibition, beginning with whale evolution (fig 2) and anatomy, for example showing a life size model of a blue whale’s heart (fig 3), which is illuminated in red light pulsating with the same frequency as a blue whale’s heartbeat. Across the museum and between the exhibits, hand painted wall decorations illustrate whale behaviour or anatomy, such as for example the feeding mechanism of baleen whales (fig.4). I especially enjoyed the displays showing the different extant whale species grouped by geographic area in which they live, such as this display of species of the Southern Ocean surrounding Antarctica (fig. 5). 

Exhibit display of whale evolution. There is a sign explaining the small reconstruction of an ancient whale. There is a drawn tree of relationships on the lower right arcing to the upper left showing how whales have changed to what we see today.
Figure 2
A museum exhibit of a life size model of a blue whale's heart. There is a sign with information in the foreground and a heart with different parts lit up.
Figure 3
Exhibit display that details the feeding mechanism of baleen whales. Behind a pane of glass there are four small models of whales showing how they feed and what the brush like teeth looks like up close.
Figure 4
exhibit dispay showing the species of the Southern Ocean surrounding Antarctica. There are scaled models of the different species mounted to the wall with a small screen in the foreground with more details.
Figure 5


But everyone agrees that the absolute highlight of the museum is the 15m (~50 feet) long skeleton of a male sperm whale that is exhibited in its own room (fig. 6). The skeleton is shown together with a replica of a human skull for size comparison, as well as a giant squid model, an important prey species for sperm whales. What is extra special about this specimen is the fact that the skeleton comes from a sperm whale that was washed up dead at the German coast in 2003 just a few kilometres from the museum. The whale weighed about 40 metric tons! Pictures of the washed up specimen are included on one of the walls, together with information on migration routes and many other interesting details. The entire room is very dark, only the whale is illuminated, the entire atmosphere feels like the deep sea. Sperm whale songs are played in the background. Everything about this is very impressive, the first step into the room takes your breath away. 

Display of a male sperm whale, with a human skull and other objects below it to aid with understanding scale. a giant squid is in the background.
Figure 6

A small side room branching off here shows very special deep sea ecosystems: hydrothermal vents! Lots of information about the geological processes leading to hydrothermal vents are shown in figures and illustrations, but the nicest part of this section is the hydrothermal vent model, which even includes tiny vent crabs and tube worms (fig. 7).

An exhibit display that is a hydrothermal vent model, which even includes tiny vent crabs and tube worms
Figure 7

Following the natural environmental sequence, one floor above the sea floor and open ocean exhibit, sea and shore birds of the local area are showcased (fig. 8). Just like in the sperm whale room, the background is full of animal sounds, in this case seagulls’ and other birds’ calls. The upper floor also includes important information about human-environment interactions, a big topic is environmental destruction through pollution but also the importance of the local Lower Saxon Wadden Sea National Park, which has a size of almost 346,000 hectares (~1,300 square miles) and is the largest national park in Germany.

Sea floor and open ocean exhibit, sea and shore birds of the local area are showcased in a room. The scene is set up like a portion of a beach with signage to explain the different animals.
Figure 8

Even though this museum is very small, through modern exhibits, the very smart use of light and background sound, detailed models and illustrations, the museum creates the perfect atmosphere for learning about marine and coastal life. I highly recommend a visit, especially if you’re looking for something fun to do on one of the many, many rainy days this area gets.

First evidence of fossilized ‘earstones’ in Cretaceous-aged cephalopods

First Cretaceous cephalopod statoliths fill the gap between Jurassic and Cenozoic forms

Summarized by: Gabrielle Scrogham completed her Bachelor’s of Marine Biology degree in 2020 and is currently a Geology Master’s student at the University of South Florida, Tampa. She is studying methods for tracking changes in diet of fish over time based on stable isotope and trace metal analysis. Their interests include marine ecology and biogeochemistry. Outside of academia, Gabrielle enjoys snorkeling, painting, and practicing martial arts.  

What was the hypothesis being tested? Cephalopods are a group of animals which include octopuses and squids. In this paper, researchers compared recently discovered fossils of cephalopod statoliths, also known as earstones, from the Cretaceous Period (145 – 66 million years ago) to older earstone fossils from the Jurassic Period (201 – 145 million years ago) and to earstones found in modern squid and cuttlefish to see how they change over time. Earstones are small, calcified parts found in the head of animals to help with navigation, movement, and balance. Earstones, or other structures for sensing balance, are found in most animals and even some plants. Statoliths in cephalopods are analogous to structures called otoliths in bony fish, as they perform the same function. The researchers hypothesized that differences in the shapes and abundances of earstone fossils would reflect evolutionary changes in cephalopod lineages. They also hypothesized these newly discovered fossils would support evidence from other paleontologists that a large-scale shift in animal dominance from cephalopods to fish occurred during the Cretaceous. 

What data were used? Five fossilized cephalopod earstones were collected from two sites in Poland and England. Several images from scanning electron microscopes were used in this study, including the newly collected earstones, a Jurassic earstone fossil, and earstones from modern squids and cuttlefish. This allowed for detailed comparisons of their shapes. The earstone structures were then compared to data compiled from previous studies on cephalopod lineages. The number of earstones found for both cephalopods and fish from each time period were also counted. 

Methods: Sediments were wet sieved using a fine (0.375 mm) mesh to separate fossils from the clay and silts in the rocks. Both collection sites were chosen due to being known Lower Cretaceous formations and for being uniquely accessible at the time of sampling. The collection site in Poland is now flooded, meaning additional samples from this area cannot be accessed. Once identified, the fossils were photographed using a scanning electron microscope. 

Results: The shape of the single earstone fossil from Poland differ than those found in England, which are more similar to earstones from Jurassic fossils. Some differences in traits include the shape and angle of the rostrum, the spur, and the lateral dome (see Figure 1 for what these features look like). Since the earstone from Poland has unique features not seen in other fossils, this likely represents a new lineage of cephalopod. There are some indications that the Poland specimen may have been a juvenile organism, so in addition to only having one fossil available, this data cannot be considered comprehensive. The earstones from England are more similar to fossils from the Jurassic, which means they may be more closely related. In addition to the analysis of the shape differences, the number of cephalopod and fish earstones were compared. Cephalopod earstones were more abundant than fish earstones in the Jurassic sediments, while fish earstones become more dominant in Cretaceous sediments. Thus, this is evidence for a shift in dominance from cephalopods to fish around 145 million years ago.

Four rows of earstone fossils pictured at different angles with significant features labelled. Figures are labelled by letter for specimen and by number for angle, with a total of six angles showing differences in the structures. Most are shaped loosely like ovals, but have thicker and thinner parts to them distorting the shape. Average size is just over 200 microns.
Images from scanning electron microscope comparing cephalopod earstones, also called statoliths, from different angles. Four samples are represented including A: modern pygmy squid; B: Cretaceous cephalopod fossil from Poland; C: Jurassic cephalopod fossil from Poland, and D: modern cuttlefish. Some distinguished features include the rostrum (r), spur (sp), and the lateral dome (ld). Scale bar = 200 microns.

Why is this study important?: Cephalopod statoliths have been found and recorded from both the Jurassic and the Cenozoic (modern), but not from the time period between those two, which is the Cretaceous (145 – 66 million years ago). This type of comparative data can reflect changes in animal lifestyle, such as shallow versus deep water environments, which can be used to reconstruct ancient habitats. Similarities between these fossils also allow researchers to look for connections in evolutionary lineages over time. Some of these fossils are also collected from sites that are no longer accessible, increasing their scientific value as it would be difficult to collect new evidence from the same regions. 

Broader Implications beyond this study: This study documents shapes of new cephalopod earstones, which could be used to examine ancient environments and reconstruct what types of animals lived in those habitats. The proposed shift in dominance of cephalopods during the Middle Jurassic to a dominance of bony fish in the Early Cretaceous would demonstrate a large-scale change in marine ecology. This dominance shift would also additionally explain the noticeable increase of fish abundance over cephalopods in the fossil record and modern oceans.

Citation: Pindakiewicz, M, K., Hyrniewicz, K., Janiszewska, K., & Kaim, A.  (2022). First Cretaceous cephalopod statoliths fill the gap between Jurassic and Cenozoic forms. Comptes Rendus Palevol, 21, 801–813. 

Gabrielle Scrogham, Marine Ecologist

Tell us a little bit about yourself. I have a Bachelors in Marine Biology and love to admire nature and the fascinating designs evolution and the planet have produced. I do art in my downtime, specifically painting, although I have interests in ceramics, woodworking, and sculpture. Most of my inspiration for art comes from interesting animals or landscapes. Swimming, snorkeling, and hiking are things I love to do given the opportunity. I like to write, discuss philosophy, and have been a martial artist for over ten years. 

What kind of scientist are you and what do you do? I am a Geology Master’s student at the University of South Florida, Tampa. I study food webs in aquatic environments and the transfer of different nutrients and metals between fish species. I am interested in using geochemical methods and data to look at ecological relationships. Specifically, I analyze tissue samples and look at proportions of different compounds to determine what level of predator they are and how quickly those chemical signals can change over time. I am also hoping to incorporate computer programming into my research by developing data processing code that can be used by any researchers using similar data. 

What is your favorite part about being a scientist, and how did you get interested in science? My favorite aspects of science are the creative challenges associated with it, such as experimental design and problem solving, and the opportunity to constantly be learning new things. In environmental science, there are multiple fields that intersect including biology, chemistry, geology, physics, ecology, and so on—in my research, I am constantly reading and learning about these things as part of my job. I was always interested in science as a kid, and specifically ocean life. Curiosity about how those organisms lived and what determined how much or how little we knew of them made me want to study science. 

Gabrielle Scrogham in mangrove swamp with field gear, including quadrat, meter stick, and jellyfish resting on platform for measuring.
Gabrielle Scrogham in a mangrove swamp with field gear, including quadrat, meter stick, and jellyfish resting on platform for measuring.

How does your work contribute to the betterment of society in general? I am hoping that the methods I am studying for my thesis can be applied to a variety of fields, including future geochemistry work, conservation biology, and fisheries management. One advantage to the geochemical methods I use, which include mass spectrometry, is that small sample sizes can be used. This means that we can monitor live fish populations without using lethal methods. The techniques are being studied with fish populations, but these can hypothetically also be applied to other biological systems, to medical research, and to different subfields of geology. 

What advice do you have for up and coming scientists? My biggest advice for other people (like me) who are beginning or early-on in their academic careers would be to focus on what you find interesting, even if you don’t have the ability to study that right away. Part of that drive or curiosity, in my mind, is critical to long-term success in science. My second piece of advice would be to learn as many skills as possible. Outside of books and coursework, knowing things like knowing how to use hardware tools or how to write computer code can be very useful. Knowing PVC plumbing can help with knowing how to put together an aquarium for study animals—and it’s stressful to only be learning it once the skill is needed immediately. Diversity in experience is also something that generally helps with confidence and being able to find a place to make yourself useful. 

Background: blurry beach with some greenery in the far back. Foreground: Gabrielle Scrogham at beach examining a sea star and brittle star.
Gabrielle Scrogham at a beach examining a sea star and brittle star.

New spider family discovered in Europe

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

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.

Andrea’s Academic Background and Career Goals

In 2017, I began my academic journey majoring in Political Science and International Affairs at Florida State University. Throughout this time, I learned how ingrained politics is in every aspect of our society and how important it is to get involved in civic duties such as voting and researching legislation on major social and fiscal issues. A significant part of politics involves the country’s history as well, which was required curriculum taught by several courses including American History, Protests in America, European History, and International Affairs. These courses taught critical material about the oppression and discrimination that has shaped the legislation still in existence today targeting all minority groups living in the U.S. These courses helped to dismantle unconscious biases and stereotypes that help us become more educated voters in the future. My courses also focused on the processes of the U.S. government system, as well as how the U.S. interacts with other countries and global entities. This is especially important when it comes to global issues where it is crucial for all states, countries, and territories to work together. In this day and age, one of the most pressing and time-sensitive issues of all is climate change.

Alt text: Woman in jean jacket and blue hat stands in front of Zion National Park canyons by river.
In Zion National Park.

In 2021, I decided to take my political science background and apply it to a master’s degree in Environmental Science and Policy at the University of South Florida. Above all, I realized that my passion has always been to protect and conserve the planet’s biodiversity and natural ecosystems. I knew how much policy determined either the protection or destruction of the environment, and I made it my goal to use my background to be on the side of preservation and restoration. Since then, I have begun my third semester of graduate school and have learned  about environmental policy, conservation in urban environments, geology, remote sensing, and environmental ethics and philosophy. 

This summer, I also had the opportunity to spend two months working with the Student Conservation Association in Yellowstone National Park. During my time there, I volunteered alongside a National Park Service conservation crew replacing a bridge with sustainable materials. The purpose of this is to ensure that people can appreciate nature in a safe way for both themselves and the wildlife and minimize impacts to areas outside of the trails. I plan to continue pursuing these opportunities that expand my knowledge on best practices for environmental policy and learning first-hand from the most experienced people in the field. These experiences have only augmented my appreciation for this field, and I hope to build a career in conservation in Florida upon graduation next May. 

Diversification Patterns of Trilobites during the Ordovician

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.

A Brief History of the Trials and Tribulations of Teaching Evolution

Faith Frings, Ohav Harris, and Kaleb Smallwood 
*Authors listed alphabetically; all contributed equally to this piece

The teaching of evolution has always been a polemical topic. People often consider evolution and religion to be in direct opposition to one another, when in actuality the two are concerned with separate realms of reality. Many teachers, and even college professors, often feel nervous about bringing up the topic because they worry about how not only students will respond, but also, in the case of K-12 educators, how their parents might react. In fact, a survey conducted in 2007 and published in 2010 concluded that roughly 532,000 students in Florida were taught by teachers who either felt uncomfortable teaching the subject or refrained from teaching evolution entirely (Fowler and Meisels, 2010). This discomfort with discussing evolution has been present since before Darwin published his theory in On the Origin of Species by Means of Natural Selection in 1859. Darwin himself feared how religious and scientific authorities would respond, as scientists such as Georges Cuvier, a lauded naturalist of the time, decried the belief that the extant species had changed much since they first came into being. This caused him to delay his publication after his return to England in 1836 (Pew Research Center, 2009). The controversy surrounding the teaching of evolution reached a head in the United States in 1925, during the Scopes trial.

The Scopes Trial of 1925 (also called the Monkey Trial) is one very infamous example of the aggravation evolution can bring about in the classroom. John Thomas Scopes, a Tennessee high school science teacher, was accused of teaching evolution, which was against Tennessee law at the time due to the Butler Act, which outlawed any philosophy that opposed creationism and taught that mankind descended from animals (Arnold-Forster, 2022). Scopes did so intentionally, as he was working with the ACLU to defy this law as the defendant. Democratic presidential candidate William Jennings Bryan aided the prosecution. Citizens acted as chimps to mock the defense. Unfortunately, since Scopes himself was on trial and not the law he acted against, the defense was not allowed to call scientists in to provide testimony and Scopes was found guilty of breaking the law and fined $100. The verdict was overturned in 1927, but this was only on a technicality. This means that for two years, it was illegal to teach evolution in schools in Tennessee. Two years may not be much in hindsight, but ideas can become entrenched in a person’s mind in that amount of time. Numerous people would have been ignorant of evolution or told that it was a lie in some cases, breeding a lack of scientific literacy that would have made it more difficult for people to accept evolution or science in general in the future. Worse still, laws of this nature persisted in places such as Mississippi and Arkansas (Arnold-Forster, 2022).

While the thoughts and feelings that led to events like the Scopes Trial may seem like a thing of the past now, such vehement sentiments against evolution have flared up more recently than one might think, leading to yet another court case regarding the teaching of evolution in 2005, this time in Pennsylvania. Kitzmiller et al. v Dover Area School District et al. differed from the Scopes Trial in two crucial ways. First, the issue was not a law banning the teaching of evolution, but the school district teaching evolution alongside intelligent design, a philosophy often used as an alternative to creationism. Second, the defense was allowed to call expert scientists as witnesses, turning the trial into something of an educational seminar for those in attendance, showing them that there is plenty of evidence in favor of evolution and that a scientific theory differs from a theory in the colloquial sense (Humes, 2008). Rather than a denial of science in favor of religion, this trial showed not only that evolution is valid, but also that it can be accepted while holding religious beliefs. Many opponents to the teaching of evolution, due to religious beliefs, came to understand the evidence for evolution over the course of the trial and came to accept it without sacrificing their religious values. While the significance of this trial and its subsequent ruling cannot be understated as they allowed the legal teaching of evolution to continue, the most important note to take from this trial is the masterful teaching put on display. Rather than chide the crowd and opposing litigants for their lack of comprehension of science, the scientists brought on by the defense were considerate, respectful, and humorous. There are important lessons to be learned from this trial by those who aspire to teach evolution or subjects such as paleontology or biology where evolution is integral to a comprehension of the subject.

For example, one important point established by the defense in the Kitzmiller case is the fact that science and religion are not mutually exclusive, but they deal in different areas of reality. Religious explanations of phenomena and other things observable in the world often tend to be supernatural, going outside of the confines of what science can and should be used to explain. Science deals strictly with the natural, observable world. Science uses what evidence exists in the natural world to come to conclusions best supported by that evidence. As such, scientific explanations of processes observable in the world do not rule out the existence of a god or other greater power. Science cannot broach the subject at all. Consequently, acceptance of evolution does not require a rejection of one’s faith, nor are the two in conflict at all. It may be helpful to point out this fact for those in a class who feel strongly about their religious affiliations to ease their worries in that regard. Additionally, this trial shows the significance of preparing thoughtful and clear  answers for any questions  raised by students in class. One outlandish argument brought up during the trial was that of irreducible complexity. It was argued that cars and planes are made using similar parts, but neither a car nor plane came from the other. Additionally, if one vital part of a car or plane was removed, the object would cease to function. It was argued that the same went for organisms. Ken Miller’s response was complete and used the relevant example of the multipurpose proteins in bacterial flagellum, which was something discussed ad nauseum in the trial, to show that organisms are not irreducibly complex (Humes, 2008). The proteins that make up the flagellum can also be used for various other functions, so it is not accurate to say that the system is irreducibly complex. In another setting, those proteins can be seen performing completely different functions. Being ready to address questions and detractors is crucial to getting an audience to listen to and respect you. Doing so while respecting people’s lack of knowledge or their skepticism is equally crucial. Through proper teaching, evolution can transition from the controversial topic it is sometimes seen as into being well-accepted as the scientific theory that it is by the public, similar to the theory of gravity or cell theory. Calmly explaining to students that we did not come from monkeys, assuaging their worries regarding religion, and encouraging scientific thinking are all important steps along this road. Evolution is just as important a scientific subject to understand as any other to allow people to understand the natural world around them and how it functions.

Works Cited

Arnold-Forster, Tom. “Rethinking the Scopes Trial: Cultural Conflict, Media Spectacle, and Circus Politics.” Journal of American Studies, vol. 56, no. 1, 2022, pp. 142–166., doi:10.1017/S0021875821000529.

Humes, Edward. Monkey Girl: Evolution, Education, Religion, and the Battle for America’s Soul. Harper Perennial, 2008.

“Darwin and His Theory of Evolution.” Pew Research Center’s Religion & Public Life Project, Pew Research Center, 4 Feb. 2009,